The closest an artist comes to painting with pure pigment is when applying soft pastel to the ground. From the earliest cave art, humans have applied powdered earths and chalks to surfaces. Some of the oldest surviving masterpieces made using coloured chalks include those of Leonardo da Vinci, and are sometimes incorrectly referred to as pastels.

An example is this drawing of Isabella d’Este from 1500, described here as using “black and red chalk, yellow pastel chalk on paper”. But there is no such thing as “pastel chalk”, any more than there is “oil watercolour”.

Pastels are much more than just a stick of pigmented chalk or coloured earth, as they’re made by mixing pigment and a bulking powder, with water containing a gum or glue, into a thick dough-like paste. That paste is dried slowly in sticks to become sufficiently firm as to be capable of being sharpened and applied to paper or another ground.

Painting in pastels requires many sticks of different colours; although those can be blended on the paper or ground, pastels don’t mix like oil paints to produce good intermediate colours. You can’t paint properly in pastels with just half a dozen different colours, but need dozens or hundreds to support a broad spectrum. This shows one of my sets of pastels, a Windsor & Newton boxed set of 200.

Careful assessment by Thea Burns has established that the earliest painter in pastels was probably Robert Nanteuil.

Nanteuil’s Portrait of Monseigneur Louis Doni d’Attichy, Bishop of Riez from 1663 is one of the first true pastel paintings, relatively small, but expertly worked. When these became popular in the eighteenth century they quickly became all the rage. Unlike oil paints applied in layers over a period of weeks, pastels adhere to the ground mechanically, and have no drying time. A good pastellist could produce a fine portrait in just a few sittings, making them far less demanding on both parties, much quicker, and of course considerably cheaper. The ‘look’ of pastel paintings also came into vogue, with flesh looking lifelike with a soft, matte finish.

Initially there were no fixatives to help the adhesion of pastel to ground, so they all had to be glazed, and even then didn’t prove as durable as a well-made oil painting. But at that price, only the very rich would care.

Next, mainstream artists started using pastels in preparatory work and sketches, here Charles Antoine Coypel’s dramatic portrait of Medea (c 1715).

One of the most brilliant of this first big wave of pastellists was Rosalba Carriera, whose work demonstrated that a good pastel painter could match the accomplishments of the best oil painters of the day. She had a painterly style at times, as shown in her rich marks in Africa, for which I don’t have a date.

In the fingers of a skilled pastellist, materials like hair and fur that had long challenged painters in oils became great strengths. Carriera’s superb Self-Portrait as ‘Winter’ from 1730-31 is a fine example, as seen in the detail below.

Look carefully and you can see individual grains of pastel that form each mark she made. She didn’t just apply her pastels dry and from the stick, but in places turned them back into a paste using water, and applied that to the paper with a brush.

The star pastellist of the middle of that century was undoubtedly Maurice Quentin de La Tour, whose works are readily seen in the Louvre and elsewhere.

De La Tour not only excelled at modelling softer surfaces and materials to which pastels are so suited, but tackled harder and glittery materials used in jewellery and the like. They’re particularly well shown in his Portrait of Marie-Josèphe of Saxony, Dauphine of France (1731–1767) (1756-60).

After de La Tour, the next brilliant pastellist was quite a contrast: Jean-Etienne Liotard, whose meticulous realism is just breathtaking. Applying his pastels to parchment rather than paper, he was able to paint painstakingly detailed works like The Chocolate Girl (c 1744-45). This shows how the medium was moving on from regular portraits.

Only when you see the patterned grain of the pastel on parchment does it become clear that this is not oil paint. I still marvel at the glass of water: surely a demonstration tour de force to make the viewer gasp in wonder.

Louise Élisabeth Vigée Le Brun’s simple portrait of a baby from about 1790 takes up from where Carriera and de La Tour had made their marks. This infant’s face is softly rendered, but their clothes are sketched in a loose style far in advance of oil paintings of the day.

Pastel painting remained popular through the nineteenth century, but its next major advances came with those around the Impressionists, rather than the core Impressionists, who overwhelmingly preferred oils.

Édouard Manet’s Woman Fastening Her Garter (1878-79) shows a motif many would associate more with Degas, and a spontaneous and sketchy style, with an emphasis on form.

Paul César Helleu was radical and exciting in his pastels; his portrait of Consuelo Vanderbilt, Duchess of Marlborough (c 1900) combines perfect, smooth blending over her face with vigorous mark-making through the fabrics and the ornate frame of the chair, as shown in the detail below.

Edgar Degas was another innovative painter in pastels, whose work encouraged Odilon Redon to take the medium on into the twentieth century.

His recurrent theme of a small sailing boat, which kept appearing in Redon’s later paintings, was expressed most extensively in his pastels. Some, like Flower Clouds (c 1903), above, show the boat sketched in roughly, his paper being dominated by nebulous patches of colour from behind.

His best-known painting of the boat, The Yellow Sail (c 1905), below, was painted in pastel too. He exploits new and more intense pigments here, for the sparkling gems in the boat, and the clothing of the two women.

Although the period since has seen new media such as acrylics, there is still nothing else like painting in pure pigment.

Reference

Thea Burns (2007) The Invention of Pastel Painting, Archetype. ISBN 978 1 904982 12 3.

Look in the log, and Visual Look Up (VLU) on an Apple silicon Mac apparently involves a great deal of work, in both CPU cores and the neural engine (ANE). This article reports a first attempt to estimate power and energy use for a single VLU on an image.

To estimate this, I measured CPU, GPU and ANE power in sampling periods of 100 ms using powermetrics, and correlated events seen there with those recorded in a log extract over the same period, obtained using LogUI. The test was performed on a Mac mini M4 Pro running macOS 15.6.1, using Preview to perform the VLU on a single image showing a small group of cattle in an upland field. Power measurements were collected from a moment immediately before opening the image, and ceased several seconds after VLU was complete.

When used like this, powermetrics imposes remarkably little overhead on the CPU cores, but its sampling periods are neither exact nor identical. This makes it difficult to correlate log entries and their precise timestamps with sampling periods. While powermetrics gives power use in mW, those measurements aren’t calibrated and making assumptions about their accuracy is hazardous. Nevertheless, they remain the best estimates available.

Log narrative

The first step in log analysis was to identify the starting time of powermetrics sampling periods. Although execution of that command left no trace in its entries, as it has to be run with elevated privileges using sudo, its approval was obvious in entries concluding
30.677182 com.apple.opendirectoryd ODRecordVerifyPassword completed
A subsequent entry at 30.688828 seconds was thus chosen as the start time for sampling periods, and all times given below as given in seconds after that time zero.

The following relevant events were identified in the log extract at elapsed times given in seconds:

• 1.3 com.apple.VisionKit Signpost Begin: “VisionKit MAD Parse Request”
• 1.3 com.apple.mediaanalysis Running task VCPMADServiceImageProcessingTask
• 1.4 ANE started and an ObjectDetectionModel run for 0.2 s
• 1.6 ANE activity and a NatureWorldModel run for 0.25 s
• 2.0 ANE activity for 0.15 s
• 2.4 ANE activity for 0.1 s
• 8.1 ANE activity and a UnifiedModel run for 0.01 s
• 8.1 PegasusKit queried Apple’s SMOOT service, the external connection used to populate the VLU window.

Thus, the ANE was run almost continuously from 1.4-2.2 seconds after the start of sampling, otherwise was used little over the total period of about 9 seconds. Over that period of activity, an initial model used to detect objects was succeeded by a later model to identify objects in a ‘nature world’.

Power and energy estimates

From the log record, it was deduced that the VLU was started in powermetrics sample 10 (1.0 seconds elapsed), and essentially complete by sample 75 (7.5 seconds elapsed), a period of approximately 6.5 seconds, following which power use was low until the end of the sampling periods. All subsequent calculations refer to that series of samples and period of time.

Sums, averages and maxima of power measurements for that period of 6.5 seconds are:

• CPU 64,289 mW total, 989 mW average, 7,083 mW maximum (10 P cores)
• GPU 3,151 mW total, 48 mW average, 960 mW maximum (20 cores)
• ANE 1,551 mW total, 24 mW average, 671 mW maximum
• total 68,991 mW total, 1,061 mW average, 7,083 mW maximum.

Thus for the whole VLU, 93% of power was used by the CPU, 4.6% by the GPU, and only 2.2% by the ANE.

For comparison, in the M4 Pro chip running maximal in-core loads, each P core can use 1.3 W running floating point code, and 3 W running NEON code. The chip’s 20-core GPU was previously measured as using a steady maximum power of 20 W, with peaks at 25 W.

As each power sample covers 0.1 seconds, energy used during each sampling period is power/0.1, thus the total energy used over the 6.5 second period of VLU is:

• CPU 6.4 J
• GPU 0.3 J
• ANE 0.2 J
• total 6.9 J.

Those are small compared to the test threads used previously, which cost 3-8 J for each P core used.

Power over time

Power used in each 100 ms sampling period varied considerably over the whole 10 seconds. The chart below shows total power for the CPU.

Highest power was recorded between samples 10-25, corresponding to 1.0-2.5 seconds elapsed since the start of measurements, and most events identified in the log. Later bursts of power use occurred at about 4.2 seconds, and between 6.6-7.1 seconds, which most probably corresponded to opening the info window and performing the selected look-up.

Almost all power use by the neural engine occurred between 1.5-2.1 seconds, correlating well with the period in which substantial models were being run.

Peak GPU power use occurred around 1.0-1.5 seconds when the image was first displayed, at 3.1-3.2 seconds, and between 6.5-7.4 seconds. It’s not known whether any of those were the result of image processing for VLU as GPU-related log entries are unusual.

Composite total power use demonstrates how small and infrequent ANE and GPU use was in comparison to that of the CPU.

Conclusions

Given the limitations of this single set of measurements, I suggest that, on Apple silicon Macs

• power and energy cost of VLU is remarkably low;
• the great majority of work done in VLU is performed in the CPU;
• although use of the neural engine may result in substantial performance improvements, VLU doesn’t make heavy demands on the neural engine in terms of power or energy use;
• VLU may appear impressive, but it’s not actually that demanding on the capability of the hardware.

Passing on from the circle of gluttons, Virgil leads Dante past the great foe of Plutus, a wolf-like creature who is chided by Virgil, and so they descend to the next circle, densely populated by avaricious misers and prodigal spendthrifts.

Plutus most probably refers here to a composite of the god of wealth, thus the root of the evil in these souls in this fourth circle of Hell, and Pluto, one of the gods of the classical underworld. Either of those roles justifies Dante’s description of him as the great enemy of mankind.

As opposites, the two groups of spirits are locked against one another, each rolling great boulders around in opposition. When their rocks crash together, they turn about and push in the other direction, and so on for eternity. Among those whose sin is avarice are many clerics, including cardinals and popes.

Virgil explains the role of Fortune in all this, that neither group of sinners can ever be satisfied with the riches that she has. Thus both the avaricious and the spendthrifts curse the angelic Fortune for their own sins.

Dante is led by Virgil past a dark spring to the swamp of the River Styx, so entering the fifth circle of Hell, where other souls covered in mud are attacking one another, punching and kicking as hard as they can. These are the sinners who were overcome with anger. Also in the swamp are their opposites, the mournful and miserable, whose breath bubbles up through the muddy waters.

The two reach the foot of a high tower, on top of which two flames are lit to signal to another tower in the far distance. This brings them a ferry, this time rowed by a man who Virgil calls Phlegyas, who is to carry the pair across the Stygian waters in his boat.

Phlegyas is a character drawn from classical legend and myth, including Virgil’s Aeneid. After Apollo raped his daughter Coronis, Phlegyas flew into a fit of rage and burned the temple of Apollo at Delphi, so the god killed him and sent him to the underworld to undergo eternal torment.

As Phlegyas rows Dante and Virgil across rough water, the spirit of Filippo Argenti, an arrogant Florentine who is hated by Dante, rises out of the water and tries to capsize their boat.

Dante tells him to be off, and Virgil assists in pushing him back into the river. They see Argenti’s ghost cast among those fighting on the shore, where he is torn apart by them, to Dante’s delight.

Their boat then approaches the moated city of Dis, in the depths of Hell (circles six to nine), where Phlegyas lands them. Virgil goes forward to secure their admission, but the gate to the city is slammed shut on him.

The artists

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, which were first published in 1857 and continue to be used. These were followed in 1867 by more illustrations for Purgatorio and Paradiso. This article looks at his paintings.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 323. Here are my solutions to them.

1: Well-guarded like West Berlin was, it holds your greatest secrets.

2: Motor nerve processes your images.

3: Cloth or worsted to connect it all together.

The common factor

I look forward to your putting alternative cases.

At first sight, this might seem a simple question to answer. Allow me to demonstrate that it’s more complex, has changed over time, and still hasn’t been resolved.

Before 1984

Although there were exceptions, before the Mac most file systems that we were likely to encounter were simple. Each file consisted of stored data, together with a small entry in the file system’s metadata containing information such as the file’s name and its time and date of creation. By convention, as that’s not stored with the file’s data, that isn’t included in its size.

The only complication here was that storage is divided up into blocks, so in addition to the file’s actual size, we’d also want to know the total size taken by the storage blocks it used, as any given block couldn’t be shared between files, a figure often known as size on disk, and dependent on the size of those blocks. If the block size is 4,096 bytes, then any file whose data was equal to or smaller than that had a size on disk of 4,096 bytes, 4 KiB or 4.096 KB. (There are 1,000 bytes in a KB, but 1,024 bytes in a KiB.)

Classic Mac OS

One of the many innovations in the first Mac was its file system MFS, in which every file has two forks, one the traditional data fork, the other a resource fork for storing structured blobs of data termed resources. As MFS was replaced by HFS and eventually HFS+, those resource forks continued.

Resource forks often reached considerable sizes, and although they are stored separately from data forks in HFS+, Apple usually gave the sizes of the two forks, as shown in this dialog, where the size of the resource fork is 117,836 bytes, almost as large as the file’s 144,788 bytes of data. Information about the size of that file’s entry in the file system data, its attributes, wasn’t given, though.

HFS+ in Mac OS X

In the early years of Mac OS X, there was controversy as to whether it should continue supporting the use of resource forks, and most of their uses were replaced by flattened data files arranged in bundles. Nevertheless, in Mac OS X 10.4, HFS+ became multi-forked with what were dubbed extended attributes or xattrs, one type being com.apple.ResourceFork, the classic resource fork. However, the practice of giving separate sizes for the data fork and other forks died.

APFS

When APFS was released in 2017, it changed the way in which xattrs are stored, as explained here. Now, each file can consist of:

1. file system attributes, stored in the file system metadata structures;
2. small xattrs of up to 3,804 bytes, stored separately from its attributes, but in file system metadata;
3. large xattrs over 3,804 bytes, typically including any com.apple.ResourceFork, stored as data streams with separate records;
4. data, stored in storage blocks as set out in their file extents.

As demonstrated using crafted files, initially the Finder ignored items 1-3 in stating file size, and just gave that of 4, the data, although it could instead still have been including resource forks, of course.

The size of this text file is given as 391 bytes in the Finder’s Get Info in High Sierra, but as you’ll see below it contains over 90,000 bytes of extended attributes that figure simply ignores.

macOS Sequoia

Here are the sizes given for another of my specially crafted demonstration files, for APFS in macOS 15.6.1 Sequoia.

According to the Finder’s Get Info dialog, this file contains 263,195 bytes and occupies 266 KB on disk. On an SSD with the standard 4 KiB block size, that should be 65 blocks, or 266,240 bytes, as given correctly. There’s something amiss with that file, though, as it claims to be a Zip archive but has an image thumbnail.

Listing its xattrs using xattred reveals no less than 14, including two of 80 KB each. xattred claims it has a data fork size of 183,136 bytes and 161,406 bytes in xattrs, making a total size of 344,542 bytes, which is nowhere near that given by the Finder. (It’s the com.apple.ResourceFork xattr, a classic resource fork, that contains the image thumbnail displayed by QuickLook instead of the normal Zip file icon.)

To discover how the Finder arrives at a size of 263,195 bytes, we need to subtract the data size from that, making 80,059 bytes, the size of the file’s resource fork or com.apple.ResourceFork xattr. So, without being explicit about forks, it’s behaving the same as in Classic Mac OS. You might find that puzzling, given that there’s another xattr of the same size that it’s ignoring, and a dozen more that don’t get a look-in. As the use of com.apple.ResourceFork xattrs has long been discouraged if not deprecated, isn’t that a strange behaviour? The more so when modern xattrs that Apple has introduced relatively recently, such as com.apple.quarantine, com.apple.macl and com.apple.provenance, are ignored.

The deeper you look into this, the more puzzling it becomes. Here are the same file’s figures as shown in Precize.

Sizes are given a few lines down, from two sources, URL Keys and the file system (FileManager), and they also differ. There’s a list of xattrs given at the foot of this window, but that only gives 12 and ignores com.apple.ResourceFork and com.apple.FinderInfo.

In the macOS API, code can obtain values for file sizes from its URL. Two keys are available, fileSizeKey and totalFileSizeKey. The first gives the data size, and the second is the same ‘total’ as that shown by the Finder, i.e. data + com.apple.ResourceFork xattr, but excluding all other xattrs. Apple’s documentation explains those as:

• fileSize is “the total file size, in bytes”
• totalFileSize is “the total displayable size of the file, in bytes. The allocated size in bytes may include space used by metadata.”

FileManager also gives the data size in its FileAttributeKey.size, but doesn’t give any for xattrs, even com.apple.ResourceFork. The size of the Metadata shown for the File system is instead calculated by totalling the individual sizes of all its xattrs, including com.apple.ResourceFork and com.apple.FinderInfo.

This may appear to be nit-picking, but data sizes are given to the exact number of bytes, and the size on disk for non-sparse files should always be within 4,095 bytes of the data size. Yet accounting for xattrs remains rooted in Classic Mac OS from 25 years ago and still pretends that xattrs either don’t exist, or don’t take any space.

In the first article of this pair looking at paintings of windmills, I covered traditional views up to the first of the pre-Impressionists. This article takes this account from around 1850 up to the period between the two World Wars. Although the development of steam power during the nineteenth century brought great changes to many industries, windmills continued to flourish until the middle of the century, and even then they only declined gradually until the Second World War.

Samuel Palmer’s Summer Storm near Pulborough, Sussex from about 1851 refers to Dutch landscape painting, in a very Kentish context. A storm is seen approaching the rolling countryside near Pulborough, now in West Sussex. On the left, in the middle distance, a small bridge leads across to a hamlet set around a prominent windmill, whose blades are blurred as they are being driven by the rising wind.

Windmill styles differ outside northern Europe. When Jean-Léon Gérôme travelled down the River Danube in about 1855, he claimed to have witnessed this moving scene of Recreation in a Russian Camp, Remembering Moldavia (1855). A group of Russian soldiers in low spirits is being uplifted by making music, under the direction of their superior. Gérôme has captured an atmosphere which few of his other paintings achieved: the marvellous light of the sky, the skein of geese on the wing, and the parade of windmills in the distance, all draw together with the soldiers in their sombre greatcoats.

The following year, JC Dahl’s Burning Windmill at Stege is an unusual fire-painting following a traditional sub-genre of the Dutch Golden Age. Although painted well before Impressionism, Dahl echoes the red of the flames in the field and trees to the left of the windmill, and even in his signature.

During the winter of 1864, Johan Jongkind returned to the Netherlands, where he painted this Winter View with Skaters, which is more overtly pre-Impressionist.

Jongkind’s watercolour sketch of a Windmill at Antwerp of 1866 is even more painterly.

Claude Monet’s second visit to the Netherlands in 1874 ensured that The Windmill on the Onbekende Gracht, Amsterdam (1874) became a part of the history of Impressionism. This shows a windmill known as Het Land van Beloften, De Eendracht or De Binnen Tuchthuismolen, which was built in the late seventeenth century, and was moved from there to Utrecht just a couple of years after Monet painted it on the banks of the River Amstel.

Frits Thaulow’s painstakingly detailed View of Amerikavej in Copenhagen (1881) shows a windmill in the background, where it’s being used to provide power to the adjacent industrial site.

Volodymyr Orlovsky’s Ukrainian Landscape from 1882 shows one of the distinctive windmills on the elevated bank alongside a major river and its more populated floodplain to the right.

It may not have been Monet who first made the visual association between Dutch windmills and fields of tulips in flower, but his 1886 painting of Tulip Field in Holland must be its best-known depiction.

When Vincent van Gogh moved to Paris in 1886, he stayed with his brother Theo in Montmartre. He painted a series of marvellous views of the remaining windmills there, including the most famous of them all, Le Moulin de la Galette (1887), in whose gardens Renoir had painted his Bal du moulin de la Galette a decade earlier.

Paul Signac’s Rotterdam. The Windmill. The Canal. Morning (1906) is a Divisionist view of a windmill in the centre of this major port.

It was a Dutch painter who took windmills from Impressionism to the modernist styles of the twentieth century: Piet Mondrian.

Piet Mondrian’s gentle nocturne of Oostzijdse Mill on the River Gein by Moonlight from about 1903 is one of several views of windmills that he painted in Impressionist and post-Impressionist style.

When he started experimenting with vibrant colour and patterned brushstrokes in about 1908, this painting of a Mill in Sunlight marks his point of departure.

The Red Mill (1911) continues Mondrian’s move towards areas of flat colour. That year he left the windmills of Amsterdam and moved to Paris. To mark his move into the avant garde of that city, he dropped the second ‘a’ from his surname, going from Mondriaan to Mondrian. He became increasingly influenced by Georges Bracque and the Cubist works of Pablo Picasso, and the purely abstract paintings for which he remains well-known today.

Serhii Svitoslavskyi’s Ukrainian Landscape with Windmills, probably from about 1911, shows a small cluster of windmills with grazing livestock.

By the end of the First World War, milling grain had become more centralised, and the hundreds of thousands of small windmills across northern Europe lost their business. A few have been preserved, and some are still used for specialist products such as stoneground flour. But the unmistakable sight of a windmill on the skyline had been lost from much of the land.

During the 1930s, the Raviliouses started spending time in Sussex, where they became close friends with Peggy Angus, whose house The Furlongs at Beddingham, East Sussex, became a second home. Eric Ravilious became particularly fond of painting the chalk downs there, as in his Windmill (1934). This isn’t a windmill in the traditional sense, but a smaller wind-driven pump to extract water from the chalk, mainly for irrigation.

Unlike Apple’s bundled apps in macOS, the great majority of third-party software needs to run on more than just the latest version of macOS. This is a challenge when there’s a major redesign of the interface, as there is in macOS Tahoe. While OS 26 may bring greater consistency across platforms, it’s also important to developers and users that it doesn’t sacrifice consistency between, say, Sequoia and Tahoe.

As I showed recently in my simple little utility DropSum, at times the appearance of windows can be very different between macOS 15 Sequoia and 26 Tahoe. DropSum uses AppKit rather than SwiftUI, and is a little unusual in applying colour to its window. This is used in a popular mechanism to indicate when that window is ready to receive a file being held over it, by changing the view colour from systemOrange to systemGreen. As that coloured view extends over the controls in the window, I have had to be careful to ensure those controls remain readable in both appearance modes, with the Reduce transparency and Increase contrast settings in Accessibility settings, and across recent versions of macOS. That hasn’t proved easy, so what you see below appears to be the best compromise I can achieve. DropSum doesn’t alter its settings or behaviour between different versions of macOS, instead relies on the host API’s appearance modes and Accessibility settings.

Although I have confirmed the observations below on individual systems, to make comparison easier here each screenshot shows two DropSum windows. The upper is running in a Tahoe beta 7 VM (where the window title is left-aligned), and the lower in Sequoia 15.6.1 on the host (where the window title is centred).

Light mode

In both light appearance modes, all boxed text is displayed in black on a white background, making their contents and controls clear. There are marked differences in the hues seen, though, with both systemOrange and systemIndigo (chosen for better contrast in labels) being more intense in Tahoe than Sequoia. As expected, Tahoe’s controls are slightly larger, and the corners of all four text boxes are rounded rather than square.

Reducing transparency made little difference in either rendering, merely whitening the window title bar.

Increasing contrast changes the intensity of some colours. In Sequoia, systemOrange is lightened, and in both windows the traffic light buttons at the top left, and the Clear button, are darkened. Otherwise the most obvious effect is the outlining of all components, including each of the controls.

Apps built to support macOS 26 thus appear consistent between macOS 15 and 26 when used in light mode.

Dark mode

Most apparent here are the contrasting effects of dark mode on the background of the four text boxes. In Sequoia, their background is the systemOrange of the coloured view, but in Tahoe it’s black. The latter makes the text contents more readable, while unselected text in Sequoia is more difficult to read.

Increasing contrast has different effects on colours when in dark mode. In Sequoia all colours including the systemOrange view become slightly lighter, whereas in Tahoe the contrast of some is enhanced, with black becoming blacker and white whiter, but there’s little discernible change in systemOrange, which remains significantly more intense than in Sequoia. systemIndigo is rendered lighter though, making it more difficult to read against the systemOrange background.

Reduce transparency

Apple describes this effect as replacing “the transparent effect used on some backgrounds in macOS with a solid background to improve contrast and readability.” In both Sequoia and Tahoe, and in both appearance modes, the only effect observed is a lightening of the window title bar, as the rest of the window is already opaque.

Increase contrast

Apple describes this as increasing “the contrast of items on the screen (such as borders around buttons or boxes) without changing the contrast of the screen itself.” Although the borders are the most prominent effect in both versions of macOS and both appearance modes, there are also colour changes that aren’t consistent between Sequoia and Tahoe.

Conclusions

• Appearance modes in Tahoe exhibit different behaviours from those in Sequoia, most markedly in dark mode. In this example, Tahoe has the effect of enhancing readability in dark mode.
• Colour rendering of systemOrange also differs between Tahoe and Sequoia.
• Reduce transparency has little effect other than making transparent views opaque.
• Increase contrast primarily adds black (light mode) or white (dark mode) borders to controls, but its small colour changes, as seen here in Tahoe, may impair readability.
• Designing an interface that behaves consistently in both macOS Tahoe and older versions of macOS is a challenge that may not always work out. Developers need to assess their app’s human interface thoroughly in multiple macOS, appearance modes and Accessibility settings.

There seems to be some confusion over what windmills are, so this weekend I show a selection of paintings of them across Europe. This article covers the period between 1500-1850, when they remained popular. From the twelfth century until the twentieth, they were a common sight on many skylines in northern Europe. Preceding the better-known vertical windmills were various horizontal designs, and windmills continued to flourish until the middle of the nineteenth century. Used wherever there was a need for driving a rotating axle, they were widely employed to grind cereals into flour, power sawmills, make paper, grind materials, and thresh corn.

Hieronymus Bosch’s uniquely imaginative paintings often featured realistic background landscapes. One recurring setting is a city based on Antwerp or his home town of ‘s-Hertogenbosch, with a windmill closest to the viewer. This appears in the centre panel of his triptych The Adoration of the Magi from about 1490-1500, for instance.

A similar windmill appears in a slightly different setting in the version of The Temptation of Saint Anthony now in Lisbon, from around 1500-10, in its right wing. This is shown in the detail below.

The Bruegels also worked amid many windmills, but none seems so prominently out of place than in Pieter Bruegel the Elder’s Procession to Calvary from 1564. Windmills were commonly built on hills, where they would benefit from the most consistent wind, but this example on a towering crag is not only geographically inappropriate, but completely impractical. It stands on a circular platform to allow the mill to rotate according to the direction of the wind, but would hardly have been above Jerusalem at the time of the Crucifixion.

More at home are the half dozen windmills clustered around the port of Dordrecht in the Netherlands, shown in Jan van Goyen’s View of Dordrecht with the Grote Kirk Across the Maas from 1644.

Rembrandt painted few non-narrative landscapes, but among them is this dramatic view of The Mill (1645-48) seen in the rich rays of twilight.

The great masters of Dutch landscape art like Jacob van Ruisdael must have painted many hundreds of windmills, of which one of the best-known is this view of The Windmill at Wijk bij Duurstede from about 1670. This small town, now a city, is on the bank of the River Rhine, an ideal location for delivering grain by barge, and shipping the resulting flour. This should have kept the mill as busy as the wind allowed, and its owner prosperous.

This view of a Landscape with Windmills near Haarlem was painted by John Constable in 1830, almost two centuries after the original made by Jacob van Ruisdael.

Windmills were also a common sight along the lower reaches of the River Thames. William Hogarth’s print from his Industry and Idleness series shows its anti-hero Idle being rowed out to join his ship at Cuckold’s Point on the River Thames, opposite what were then the West Indian docks, between Limehouse and Greenwich. Long after these windmills had gone, this section of the river was still involved with the grain trade.

There were other windmills upstream of the city of London too. In what must be Thomas Girtin’s most famous painting of The White House at Chelsea, from 1800, the artist looks upstream of the River Thames from a location close to the modern Chelsea Bridge. The landmarks shown include, from the left, Joseph Freeman’s windmill (or Red House Mill), a horizontal air mill, the white house close to where Battersea Park is now, Battersea Bridge, and Chelsea Old Church. Girtin painted this when he was twenty-five, and showing greater promise than his rival JMW Turner. Two years later Girtin died of asthma.

A few years later the topographic painter John Varley painted this close-up view of the same Red House Mill, Battersea, Surrey, looking back in the opposite direction.

Some of the well-known windmills supplying the city of Paris with its flour were those above its outskirts on Montmartre Hill. Georges Michel’s view of The Mill of Montmartre was probably painted in about 1820, by which time there were only a few left.

Richard Parkes Bonington probably painted Barges on a River in around 1825-6 when he was travelling near the French town of Nantes. The windmill seen behind the trees is reminiscent of seventeenth-century Dutch landscape painting.

During his detailed realist period early in his career, Johan Jongkind painted this View of Maassluis in Winter (1848). Following the long tradition of landscape painting in the Netherlands, he sets his horizon low and paints a wonderful winter sky.

Here are this weekend’s Mac riddles to entertain you through family time, shopping and recreation.

1: Well-guarded like West Berlin was, it holds your greatest secrets.

2: Motor nerve processes your images.

3: Cloth or worsted to connect it all together.

To help you cross-check your solutions, or confuse you further, there’s a common factor between them.

I’ll post my solutions first thing on Monday morning.

Please don’t post your solutions as comments here: it spoils it for others.

Inside every Intel Mac with a T2 chip, and every Apple silicon Mac, is a secure enclave, originally referred to as its security enclave. The subject of a flurry of Apple’s patents from 2012 onwards, this was introduced in the A7 chip inside the iPhone 5s and iPad mini 3, 12 years ago in September 2013, where it brought biometric authentication in Touch ID.

iPhone 5s

Protecting the most important secrets in a computer is a great challenge. No matter how secure you try to make the main processor and memory, as they’re exposed to direct attack, isolation can only be relative and temporary. An alternative approach is to move the most secure data and its processing into a secure enclave and its processor, and that’s the architectural solution chosen by Apple in what it patented as a security enclave, filed in September 2012, a year before its release in the iPhone 5s. Engineers credited for that patent are Manu Gulati, Michael J Smith and Shu-Yi Yu.

Successive iPhone chips steadily improved their secure enclaves, and by the time the iPhone 7 was introduced in September 2016, with its A10 Fusion chip, its secure enclave was handling encryption and authentication but not replay prevention. It also had EEPROM secure storage, and an AES engine with DPA protection and lockable seed bits. When the first Intel Mac with a T1 chip was released a couple of months later, that was based not on the A10 but the S2 used in the Apple Watch Series 2. The T1 thus doesn’t really have a secure enclave as such, although it supports Touch ID.

An early and thorough account of these secure enclaves was presented by Tarjei Mandt, Mathew Soling and David Wang at Black Hat USA in 2016. This appears to be the only such account apart from the section in Apple’s Platform Security Guide, most recently updated in December 2024. Apple’s engineers continued to gain new patents, covering trust zone support (filed in 2012), key management (filed in 2014), and most relevant to Macs, Pierre Olivier Martel, Arthur Mesh and Wade Benson’s patent for multi-user storage volume encryption, filed in 2020.

T2 chip

The first Macs with a true secure enclave are those with a T2 chip, starting with the iMac Pro in December 2017. Those are based on the same A10 Fusion chip from the previous year, and were already lagging the iPhone 8 in this respect.

The T2 secure enclave is another co-processor system, run by a Secure Enclave Processor (SEP), a 32-bit ARM CPU running its own operating system, sepOS, based on a specialised L4 microkernel completely different from those used by Macs and Apple’s devices. It has its own secure storage (EEPROM), and a Public Key Accelerator for signing and encryption/decryption using RSA and ECC methods. Outside the enclave is a dedicated AES256 encryption/decryption engine built into the data transfer path between the internal SSD and main system memory.

M-series chips

The big leap forward for Macs was the release of the first models featuring M1 chips, which caught up with the features of late versions (after autumn 2020) of the A12 and A13, with Apple’s second generation Secure Storage Component.

Perhaps the most significant of its improvements are measures to prevent replay attacks. Those are best illustrated with FileVault. Let’s say that you didn’t enable FileVault at first, but left your Apple silicon Mac to handle the encryption of its internal Data volume without the added protection of your password. That would mean that its volume encryption key (VEK) was generated internally by the Secure Enclave, and stored there. If you then turned FileVault on, the VEK would be encrypted using your password and the hardware key. In the T2 chip, it might be possible to use the old VEK to decrypt the volume. In the secure enclave of an M-series chip, that type of replay attack is prevented by the revocation of all previous events and records.

Other improvements include the use of second generation secure storage incorporating counter lockboxes to enforce limits on the number of passcode attempts allowed, instead of an EEPROM, and a better Public Key Accelerator.

Currently, the secure enclave is known to protect the following:

• encryption keys for Touch ID, FileVault, and the Data Protection (iCloud) keychain (but not file-based keychains);
• that Mac’s Unique ID (UID) and Group ID (GID);
• Touch ID control, and (on older devices not Macs) Face ID using a secure neural engine; in recent devices and M-series chips, that’s implemented as a secure mode in the main neural engine (ANE);
• Apple Pay handling;
• Activation Lock, through the Owner and User Identity Keys;
• signing and verification of LocalPolicy for boot environments (Apple silicon).

Communication between the CPU and SEP is performed using a dedicated mailbox whose function is detailed in Apple’s patents. Further information is also provided in the Platform Security Guide.

FileVault encryption

It has been stated widely (even here) that the secure enclave in T2 and Apple silicon chips contains a hardware encryption/decryption unit and acts as the internal SSD’s storage controller. In fact, as shown in the original patent of Martel and others, and now in the Platform Security Guide, the AES engine responsible is located outside the secure enclave, together with the Flash controller, and has a secure link to the enclave.

During SEP boot, it generates an ephemeral key to wrap keys to be used by the AES engine for encryption and decryption. That key is sent from the secure enclave to the AES engine over the dedicated connection between them, then used to protect keys transferred from the enclave to the AES engine. That ensures an unprotected key is never exposed outside the enclave and AES engine.

The Apple silicon secure enclave is by no means unique. ARM TrustZone, other Trusted Execution Environments, and Trusted Platform Modules offer similar features and facilities. However, the secure enclave is unusual because it has been integrated into all Macs with T2 or Apple silicon chips, and all Apple’s recent devices, and can’t be disabled or bypassed.

References

Manu Gulati, Michael J Smith and Shu-Yi Yu, US Patent 8,832,465 B2, Security enclave processor for a system on a chip, filed 25 September 2012, granted 9 September 2014.
R Stephen Polzin, James B Keller, Gerard R Williams, US Patent 8,775,757 B2, Trust zone support in system on a chip having security enclave processor, filed 25 September 2012, granted 8 July 2014.
R Stephen Polzin, Fabrice L Gautier, Mitchell D Adler, Conrad Sauerwald and Michael LH Brouwer, US Patent 9,419,794 B2, Key management using security enclave processor, filed 23 September 2014, granted 16 August 2016.
Pierre Olivier Martel, Arthur Mesh and Wade Benson, US Patent 11,455,432 B1, Multi-user storage volume encryption via secure processor, filed 8 June 2020, granted 27 September 2022.
Tarjei Mandt, Mathew Soling and David Wang (2016), Demystifying the Secure Enclave Processor, Black Hat USA 16 (PDF)
Apple, Platform Security Guide
Wikipedia’s overview of Apple silicon chips.

Gates as a means of access through the walls of fortified cities have ancient origins, but it wasn’t until the Etruscans and the Romans that they acquired their own deity, notably in the Roman god Janus with his two faces. His association with gates, and the start and end of war, gave rise to an interesting tradition in classical Rome: the gates at each end of an open enclosure associated with the god were kept open in times of war, and closed when the city and empire was at peace. Opening the gates of the temple of Janus was therefore a mark of starting a war.

In Rubens’ Temple of Janus from 1634, those gates, here imagined to be those of a temple, are being opened to let a warrior through to battle. Above that doorway is a statue of Janus with his two faces.

In Biblical narratives, the prominent account involving gates, other than those of heaven or hell, occurs at the start of the Passion of Jesus, in his triumphal entry into Jerusalem riding a donkey, since celebrated by Palm Sunday. This has been depicted in two significant works in the late nineteenth century.

Gustave Doré painted several versions of Christ’s Entry into Jerusalem including this preparatory sketch, in preparation for his final huge version exhibited at the Salon in 1876, measuring 6 by 10 metres.

In 1897 Jean-Léon Gérôme painted his account of The Entry of Christ into Jerusalem. According to all four gospels, Jesus descended from the Mount of Olives, and as he proceeded towards Jerusalem, crowds laid their clothes on the ground to welcome his triumphal entry into the city. Aside from being one of the major events in the Passion to be shown in paintings, for Gérôme this may have had another reading. Just a few years earlier, his paintings were being welcomed by throngs at the Salon, and commanded huge sums when sold. A short time later, his work was largely ignored, and he may have seen himself as being prepared for crucifixion in public.

The gate of hell is featured in two of the major Christian literary works of the early modern period: Dante’s Divine Comedy (c 1308-1321) and John Milton’s Paradise Lost (1667).

At the start of Dante’s Inferno, the ghost of Virgil leads the author to the gate of Hell. Inscribed above it is a forbidding series of lines leaving the traveller in no doubt that they’re going to a place of everlasting pain and tortured souls. This culminates in the most famous line of the whole of the Divine Comedy:
Lasciate ogne speranza, voi ch’intrate
traditionally translated as Abandon hope all ye who enter here, but perhaps more faithfully as Leave behind all hope, you who enter, and is seen written in William Blake’s own hand below.

It’s also William Blake who depicts Satan at the gates of hell in his paintings to accompany the second book of Milton’s epic.

Two versions, that from the Thomas set above, and below that from the Butts set, show Satan at the gate of hell, on his way out and heading for heaven.

Although the phrase pearly gates, derived from a description of the gate to heaven in the book of Revelation, has been in common use, few if any paintings have depicted them literally. However, in paintings of secular life they can have symbolic significance.

James Tissot painted The Farewells soon after his flight to London in the summer of 1871. This couple, separated by the iron rails of a closed gate, are in late eighteenth century dress. The man stares intently at the woman, his gloved left hand resting on the spikes along the top of the gate, and his ungloved right hand grasps her left. She plays idly with her clothing with her other hand, and looks down, towards their hands.

Reading her clothing, she is plainly dressed, implying she was a governess, perhaps. A pair of scissors suspended by string on her left side would fit with that, and they’re also symbols of the parting taking place. This is reinforced by the autumn season, and dead leaves at the lower edge of the canvas. However, there is some hope if the floral symbols are accurate: ivy in the lower left is indicative of fidelity and marriage, while holly at the right invokes hope and passion.

Edmund Blair Leighton’s Regency scene of The Elopement from 1893, shows a woman leaving home to run away with her lover, the oarsman in the boat. She closes the gate on her old life as she looks back and reflects, before boarding the boat in which she will start the journey of her new life.

With careful observation and a little knowledge of the startup sequence of an Apple silicon Mac, you can learn a lot about what can and can’t happen during that sequence. This article explains how, with examples from the log of a Mac mini M4 Pro.

In broad terms, startup of an Apple silicon Mac consists of the following sequence of events:

• Boot ROM, which ends in DFU mode if there’s a problem, otherwise it hands on to
• the Low-Level Bootloader (LLB) and iBoot (Stage 2), the firmware, that should end in validating and running
• the kernel, which initially runs on a single CPU core before starting others up and launching launchd, and later
• unlocking and accessing the Data volume, and progressing to
• userspace.

The opening entry in the log is the boot announcement of
=== system boot:
followed by the boot UUID. There’s then a gap of 5 seconds or more before the next entry, which marks the start of kernel boot. Those seconds are the silent phase during which the LLB and iBoot are doing their thing. They don’t write to the Unified log, but leave fragments of cryptic information known as breadcrumbs, which you can’t make use of. The kernel then writes its usual welcome of
kprintf initialized
and the following four seconds or so are filled by log entries from the kernel.

Wallclock adjustment

During this phase, the system clock is synchronised, and wallclock time adjusted, usually twice in rapid succession. This is obvious by step changes in timestamp, usually putting the clock back by several seconds in the first sync, then putting it forward slightly in the second. These play havoc with the timestamps, as you can have two or even more instances of the same time being recorded in the log. Beware of the entries
=== system wallclock time adjusted

Early during the kernel phase, it starts up all the other CPU cores in the chip, and records that in the log. Entries become progressively more varied after launchd is loaded, and this first userspace boot (without Data volume access).

Data volume unlock

With FileVault enabled, by this stage macOS still doesn’t have access to the Data volume. That means all the code run so far, and almost all the data, are immutable, locked in the firmware or the Signed System Volume (SSV). The firmware does access LocalPolicy from another container in the internal SSD, and there’s always the NVRAM, but there’s no access to anything in /Library, including the many property lists there. This also means that processes running before the Data volume is unlocked and mounted can’t write to storage.

Around 10-15 seconds after the start of booting, the login window is displayed, ready for the user to enter their password. Once that has been entered, there’s a watershed moment:
30.845097 com.apple.loginwindow Attempting to unlock the data volume <LFVolume: 0x6000001b8e40: [UUID]: Data>
30.883172 "AppleSEPKeyStore":3814:0: Sending notification for volume [UUID] unlocked (action 1, handle -842987934)
30.885459 com.apple.login volume <LFVolume: 0x6000001b8e40: [UUID]: Data> was unlocked
30.886129 com.apple.loginwindow Unlocked data volume <LFVolume: 0x6000001b8e40: [UUID]: Data>
30.886154 com.apple.loginwindow FileVault volume unlocked, allow authorization
30.887562 com.apple.loginwindowLite -[LWLSystemUnlock unlockSystem]:439: Authorization was successful
30.887587 com.apple.loginwindowLite -[LWLSystemUnlock unlockSystem]:447: logging in user hoakley
The times on those entries were deliberately delayed, as I pressed the Return key for password entry after 30 seconds had elapsed, a good 10 seconds later than I could have done so.

Shortly after that, the kernel manager shuts down, a great many kernel space processes are handed over to continue in userspace, and you’ll then see the kernel report
userspace boot

Before the Data volume is unlocked, log entries are frequent, but hardly a torrent, at around 1,000 per second, and more than 25% of them are written by the kernel. Once the kernel has booted userspace and the Data volume is accessible, log entries are written far more frequently, at an average rate of 5,000 per second, often even higher, with less than 10% of them coming from the kernel.

Phase summary

• Boot ROM, entering DFU mode or handing over to
• Low-Level Bootloader (LLB) and iBoot (Stage 2) firmware, without log entries, handing over to
• the kernel, with wallclock adjustments, until
• Data volume unlocking, then into
• userspace and access to /Library and user files.

In the nineteenth century many painters paid the bills by illustrating books, often those intended for children. Two in particular are now known as illustrators, overlooking their fine art: Gustave Doré and Walter Crane. In this series of three articles I look at the work and career of the latter, who was one of the leading children’s illustrators who shaped how children’s books would look well into the twentieth century.

Crane was also an accomplished and recognised painter, an enthusiastic fan of the Pre-Raphaelite Movement, a close friend of William Morris, a key member of the Arts and Crafts movement, and an overt and active Socialist.

He started his training as an apprentice to the wood-engraver William James Linton, between 1859 and 1862. In 1863 Edmund Evans employed him to illustrate ‘toy books’ for children, and he continued to create book illustrations until well after 1900. In the later years, he extended his repertoire to include special editions of the Faerie Queene, a volume of Arthurian legends, and a book about the New Forest.

His career in painting had started slightly earlier, though, when his first work was accepted by the Royal Academy in 1862, and he continued to paint independently of his illustrations.

Crane was one of the first artists to base a painting on Alfred Lord Tennyson’s (1809–1892) poem The Lady of Shalott, published in 1833 and 1842. This tells part of the Arthurian legends, that of Elaine of Astolat, as given in an Italian novella from the 1200s.

The Lady of Shalott lives in a castle connected to Camelot by a river. She’s subject to a mysterious curse confining her to weaving images on her loom, and must not look directly at the outside world. One day, while she sits and weaves, she catches sight of the knight Lancelot. She stops weaving and looks out of her window directly towards Camelot, invoking the curse. She abandons her castle, finds a boat on which she writes her name, then floats downriver to Camelot, dying before she arrives. Lancelot sees her body, and the poem ends:
But Lancelot mused a little space
He said, “She has a lovely face;
God in his mercy lend her grace,
The Lady of Shalott.”

Crane’s Lady of Shalott from 1862 shows her white in death, laid out in her boat, tresses and flowing sleeve draped over its gunwhales into the still water at the river’s edge. This is set in an ancient wood, in dramatic twilight, presumably dusk. This painting was accepted for exhibition at the Royal Academy, and must have influenced JW Waterhouse’s much better-known version just over 25 years later (below).

The following year he chose a story from the Old Testament. According to various sources in the Bible, Boaz was a wealthy landowner in Bethlehem who noticed Ruth, a widow in such difficult financial circumstances that she came to glean grain from his fields. Boaz invited her to eat with him and his workers, and started deliberately leaving grain for her to glean. Because they were distantly related, Ruth then asked Boaz to exercise right of kinship and marry her. They had children, and David was their great-grandson.

Crane’s painting, which is in oils despite resembling a watercolour illustration, shows the couple at the end of lunch, during Ruth’s gleaning. Their dress is an odd composite of the Biblical and Arthurian. She is looking down at her hands, as if contemplating grain held in her left palm. He has turned and looks towards her. In the background Boaz’s workers continue the harvest, and saddled horses are idle, a castellated house set in the crag behind them.

Two years later he was one of the first artists to depict John Keats’ ballad of La Belle Dame Sans Merci, written in 1819, and later revised slightly. It gives a simple story of love and death, including the verses:
I met a lady in the meads,
Full beautiful, a fairy’s child;
Her hair was long, her foot was light,
And her eyes were wild.

I made a garland for her head,
And bracelets too, and fragrant zone;
She looked at me as she did love,
And made sweet moan.

I set her on my pacing steed,
And nothing else saw all day long,
For sidelong would she bend, and sing
A faery’s song.

The ‘belle dame’ of the title is shown riding side-saddle on the knight’s horse, flowers in her long, flowing tresses, and the knight, clad in armour and heraldic overgarments, holds her hand. This appears to have inspired later paintings by Arthur Hughes and Frank Dicksee.

There’s some dispute over whether this triptych from about 1870 shows The Danaïdes, or Europe, Asia, Africa, or maybe both. The fifty daughters of Danaus were forced to marry the sons of their uncle Aegyptus, but their father told them to kill their husbands on their wedding night. All but one followed his instructions, for which they were condemned to eternally carry water in leaking vessels. Alternatively, the woman on the left could be African, that on the right Asian, and the woman in the middle European.

Crane married in 1871, and the couple travelled in Europe for the next two years. They visited Florence where they must have seen some of Botticelli’s paintings.

Botticelli’s The Birth of Venus (c 1486) is one of the world’s most famous paintings, and shows the goddess Venus, when she was born from the waters as an adult, arriving at the shore.

Crane bases his Renaissance of Venus (1877) on Botticelli’s painting, and links her rebirth back to the Renaissance. She is stood at the edge of a placid sea, the water just above her ankles. Three attendant graces are also getting out of the water in the middle distance, but appear to have been bathing. A train of white doves flies down and behind Venus, to start landing on the shore at the right. In the distance are the remains of a classical building at the water’s edge, and what appears to be a section of Mediterranean coastline. Further out at sea, a sailing boat passes by. Crane painted this in tempera, just as Botticelli did.

In classical Greek mythology, Persephone, daughter of Zeus and Demeter, is the queen of the underworld. She acquired that role when Hades, god of the underworld, was overcome with love and lust from one of Cupid’s arrows, and had seen Persephone picking flowers with friends. Hades then abducted her to be his queen.

Crane’s Fate of Persephone from 1878 shows her at the moment of abduction. She had been picking spring flowers in the meadow with the three other women shown at the left. Hades brought his chariot, complete with its pair of black horses symbolising the underworld, and is seen gripping Persephone’s right arm, ready to move her into the chariot and make off.

It’s remarkable that, although their body language is emphatic and clear, each of the five figures has a completely neutral facial expression. This helps its appearance as a frieze, an effect enhanced by Crane’s use of oil and tempera. The horses appear in complete contrast, champing at their bits and poised to set off at a gallop.

The following year he’s believed to have painted this elaborate setting of George Howard, 9th Earl of Carlisle, and Rosalind, Countess of Carlisle, seated in the gardens at Naworth Castle, Cumbria, with a companion, standing holding a book. However, it was later signed clumsily by “E Burne Jones”, possibly in an attempt to pass it off as a more valuable work.

This couple had married in 1864, and were ardent supporters of the Pre-Raphaelite Movement, and friends of Crane since they were both students, Edward Burne-Jones and William Morris. Howard was an accomplished painter who had trained at Heatherly School of Fine Art in London, and later became a trustee of the National Gallery in London.

Edward FitzGerald’s translation of a selection from the poetry attributed to Omar Khayyam (1048-1131) was published in 1859, was popularised from 1861, and appreciated by several of the Pre-Raphaelite Movement. Walter Crane’s painting from 1882 was accompanied by the following quotation from FitzGerald’s Rubaiyat:

Would that some winged angel ere too late
Arrest the yet unfolded Roll of Fate,
And make the stern recorder otherwise
Enregister, or quite obliterate!

Ah love! could you and I with him conspire
To grasp this sorry scheme of things entire,
Would we not shatter it to bits – and then
Remould it nearer to the heart’s desire!

A male winged angel is on bended knee before the figure of Time, who holds his scroll recording the destiny of all mankind. The angel’s hands are intertwined with those of Time: both right hands grasp the quill used to record destiny, both left hands are at the other end of the scroll. The angel looks up pleading at Time, but Time looks down at him with a frowning scowl. In front of the dais on which the angel kneels and Time sits is an hour glass. The whole is set inside a circular building revealing the stars through its roof, like a planetarium.

Endymion was a classical Greek mythological character, an Aeolian shepherd. Although accounts differ, some tell that Selene, Titan goddess of the moon and in Roman terminology, Diana, fell in love with Endymion, when she found him asleep one day. Selene asked Zeus to grant him eternal youth, resulting in him remaining in eternal sleep. In spite of his somnolence, she still managed to have fifty daughters by him. In Crane’s beautiful pastoral watercolour of Diana and Endymion from 1883, he is fast asleep in a meadow. Diana is in her hunting role with her dogs, bow and arrows. Endymion’s flock of sheep is in the distance.

References

Wikipedia

O’Neill M (2010) Walter Crane. The Arts and Crafts, Painting, and Politics, 1875-1890, Yale UP. ISBN 978 0 300 16768 9.

Local Spotlight search problems appear common, and are all too often tackled blindly by forcing a volume’s indexes to be rebuilt. Although that can sometimes resolve the problem, without knowing what its cause is, it can just waste time and effort. Indeed, in some cases rebuilding the indexes can worsen the problem, at least temporarily. This article explains how you can use SpotTest 1.1 to perform systematic testing and arrive at a diagnosis before hazarding a guess at what the treatment should be.

1. Spotlight settings

Before opening SpotTest, check that Spotlight settings are in order, and don’t exclude the volume or folder you’re trying to search, or the document type you’re looking for. Then open Activity Monitor and watch its CPU % listing to verify that Spotlight isn’t currently in the process of reindexing or performing other maintenance to its indexes. If it is, delay testing until those have completed. Searching using Spotlight while it’s actively working on its indexes will give odd results, or none at all.

If you’re going to use SpotTest on any location with privacy control, such as your Home Documents folder, or an external disk, consider adding the app to the Full Disk Access list in Privacy & Security settings, before opening it.

2. Home folder test

Even if your interest is in a different volume, you should perform a basic test of a new test folder in your current Home folder, to establish a baseline and confirm that Spotlight is working there.

Open SpotTest and set it to defaults, with a Term of cattle, a Scope of [Home], and both Search Keywords and Search EXIF ticked.

Click the Create Tests tool (the leftmost of the tools) to create the folder of test files at the top level of your Home folder. Make a note of the time you do this to the second.

About 10-15 seconds after that, click either the Run NSMetadata test or Run mdfind test tool. You should then see a list of files found, including those in the test folder ~/0_SpotTestFiles, including A, B, C, D, E, F, G, K, L, M

If you don’t see those listed, open Mints and use the Log Window button in its Spotlight section to obtain a log extract from the time the test files were created, or use LogUI to do the same. You’ll then need to look at that log extract to see if there are clues as to why indexing didn’t take place in the period.

Leave the test folder where it is, and anything from 1 hour to 2 days later, repeat the search using either or both of those tools. Once additional indexing has been undertaken:

• NSMetadata should now find A, B, C, D, E, F, G, I, K, L, M but not H
• mdfind should now find A, B, C, D, E, F, G, H, I, K, L, M.

I is found by the Live Text process, and H by Visual Look Up, the latter only being found by the mdfind search.

These tests have demonstrated:

• mdworker and mds indexing of files supported by system mdimporters;
• delayed background mediaanalysisd image analysis and mds indexing of Live Text and Visual Look Up content.

To match test files with their importers, click the Check importers tool. Note that file L doesn’t use a plugin, and N uses a plugin but can’t be found because the search term is inside an image in the PDF document, which currently isn’t recoverable content.

3. Custom mdimporter

Many apps come with their own custom mdimporter that provides Spotlight indexing support for document types not supported by macOS. In the past, these were normally installed in /Library/Spotlight, but more recent apps typically keep them inside the app bundle in Library/Spotlight. These can be tested easily.

Create and save one of those custom document types, so that it contains the word cattle in a way that should be searchable by Spotlight. Copy that document to the ~/0_SpotTestFiles folder, wait 10-15 seconds, then repeat the test search. You may well notice that NSMetadata search doesn’t find your custom test document, but mdfind does. This is because of the difference in the search criteria they use.

You should also click the Check importers tool to check that the correct mdimporter was recognised and used for the custom document type.

4. Volume test

If Spotlight works correctly with the test folder in your Home folder, you may wish to progress to testing a different volume or location. Having created its test folder in ~/0_SpotTestFiles, copy that to the other location. Before you try to change the Scope of the search, click on the button to list available volumes, then select the volume containing the copied test folder in the Scope menu.

When you perform the two types of search on that volume, the same rules should apply as to which will be found. Note though that finding files I and H can take much longer, or they may not appear at all.

5. Search term test

When you’re confident that a search term of cattle can be found reliably, you may wish to extend your testing to other terms. Take care when choosing custom terms, as you want to be confident that they should be found, but not in such numbers that the results are overwhelming. You will also need to create your own test files containing the custom term.

Diagnosis

SpotTest can thus provide key information on:

• delay or absence of find following creation of test files. If no indexing activity is seen in the log, that suggests indexing failure. If the test files are indexed promptly, it suggests search failure;
• delay or absence in finding files H and I, indicating an indexing failure;
• failure of a custom mdimporter to index a custom document type;
• failure to index another volume.

Those should fit in with the overall scheme used by Spotlight, as shown below.

Happy hunting!

Another of the new genres to emerge and develop in the Dutch Golden Age is animal painting. This appears to have started among Flemish painters at the end of the sixteenth century, but didn’t become popular until about 1640, when a succession of painters in the Dutch Republic depicted domestic animals as part of their landscapes.

Aelbert Cuyp is thought to have painted this Landscape with Cattle when he was only about nineteen, in 1639. It’s set against the background of the city of Dordrecht, the oldest in the two provinces of Holland, and situated on the Rhine-Meuse-Scheldt river delta. The herdsman and animals in the foreground are engaged in diversions from that landscape: the man is taunting a billy goat, while the cow at the far right is urinating copiously.

Cuyp continued to develop his landscapes with more diverse themes. Orpheus with Animals in a Landscape from about 1640 is one of at least two different paintings he made of this story from mythology. Here he has included a wide range of both domestic and exotic animals and birds, including a distant elephant, an ostrich, herons and wildfowl.

His paintings of domestic animals also took him indoors, for example in this fascinating painting of Sheep in a Stable from about 1645. The sheep are faithfully depicted, and surrounded by objects suggesting elements of a still life. In the foreground are empty mussel shells, a couple of earthenware pots, and two wickerwork baskets with some scarlet cloth. He also renders the texture of the fleeces using painterly brushstrokes, particularly that of the standing ram.

Artists who had travelled to lands in the growing Dutch Empire sent back paintings of the animals they saw there. Albert Eckhout, who had been born in Groningen, accompanied John Maurice, Prince of Nassau-Siegen, Dutch governor of Brazil, when he landed at Recife in January 1637, to document local inhabitants and wildlife.

Eckhout’s Study of Two Brazilian Tortoises is believed to have been painted in Brazil in about 1640.

Paulus Potter was probably the first dedicated animal-painter, through his brief career in Delft, The Hague and Amsterdam.

Potter’s first masterpiece is The Bull (also widely known as The Young Bull) (1647), which is nearly life-sized, and almost hyperreal in its surface details. Originally intended just as a portrait of the central bull, Potter enlarged the canvas to accommodate (from the left) a ram, lamb, ewe, herdsman, cow, and above them a bird of prey, possibly a buzzard. Beyond them are more cattle in the meadows, which recede to the church of Rijswijk, which is between Delft and The Hague.

He went on to paint portraits such as Two Pigs in a Sty (1649), featuring two hairy pigs at rest. Many of the older breeds of pig were more hirsute than modern varieties, and Potter has painted their coats realistically, as well as skilfully lighting the face of the sow sat on her haunches.

Potter’s Cows Grazing at a Farm from 1653 was one of his last paintings, and apart from its meticulous detail, its rich lighting effects might be more typical of Corot two hundred years later. Potter died tragically young the following year, but the new sub-genre was taken up by others, including Adriaen van de Velde.

Van de Velde’s undated Milkmaid with Cow and Goats in Front of a Barn is a farmyard delight, with the cow being milked looking directly at the viewer.

The Hut (1671) was one of van de Velde’s last paintings, and has long been esteemed in the Netherlands. It’s one of his most natural compositions, sparkling with bright colour in the clothing and animals. The artist even adds the reality, perhaps as a touch of humour, of some fresh cowpats.

Jan Weenix’s early painting of a Landscape with Shepherd Boy from 1664 reveals his true forte in the realistic depiction of the sheep and dog.

Some specialised even further: Melchior d’Hondecoeter concentrated on birds and game.

Concert of the Birds (1670) is one of his more elaborate paintings featuring a wide range of native species.

D’Hondecoeter painted this huge Portrait of Three Children in a Landscape with Game in the latter half of the 1600s. The children appear to have taken to field sports at a very early age, and have here amassed an impressive ‘kill’, with their muzzle-loading gun, although I hope that an unseen adult may have had a hand in its use. The lone tortoise being ignored by each of the children and dogs is slowly crawling its way towards them, as if it has just emerged into the wrong painting.

DropSum is my simple drag-and-drop utility for checking MD5 and SHA256 hashes, and using them to compare pairs of files to see if they’re identical.

This new version brings two changes:

• Text entered in its two text boxes, where you paste hashes, is now cleaned of any spaces and hyphens, and set in lower case, before being used as a hash, although it’s not altered in the text box. This should save you having to edit what you paste there. Thanks to Panda for requesting that.
• I have tried to improve readability when in dark mode in Sequoia and earlier. Thanks to EcleX for requesting this.

That said, the window’s appearance is a compromise between what looks best in Sequoia, and that in Tahoe. To see what I mean, here’s the same app, in its new version 1.2, in two versions of macOS, both in dark mode with Reduce Transparency enabled.

In macOS Tahoe there’s strong contrast throughout, and all text is readable, as it is in light mode.

Yet in macOS Sequoia, white text in unselected text boxes is shown against its orange background, rather than grey or black.

I have a feeling we’re in for an autumn of similar visual discrepancies appearing in other apps, whether or not they’ve been built for compatibility with Tahoe.

DropSum 1.2 for Big Sur and later, including Tahoe, is now available from here: dropsum12
from Downloads above, and from its Product Page.

Its MD5 hash is 9370f006d65eb3f6f65ab97dc78ce345
and SHA256 is f898b580138dc05d273c8b7f16321ad6d6754d76ecabf1c49fcac1d32bc156e6

Enjoy!

Apple has just released its weekly update to XProtect for all supported versions of macOS, bringing it to version 5312. As usual, Apple doesn’t release information about what security issues this update might add or change.

This version adds three new detection rules: MACOS.SOMA.AUENB augmenting rules for the Soma/Amos family, MACOS.DUBROBBER.CHBI for another Dubrobber variant, and MACOS.ODYSSEY.LELI for an additional Odyssey variant.

You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.

A full listing of security data file versions is given by SilentKnight and SystHist for El Capitan to Tahoe available from their product page. If your Mac hasn’t yet installed this update, you can force it using SilentKnight or at the command line.

If you want to install this as a named update in SilentKnight, its label is XProtectPlistConfigData_10_15-5312

Sequoia and Tahoe systems only

This update has now been released for Sequoia via iCloud. If you want to check it manually, use the Terminal command
sudo xprotect check
then enter your admin password. If that returns version 5312 but your Mac still reports an older version is installed, you may be able to force the update using
sudo xprotect update

In the long-distant past, our ancestors discovered that processing some natural products created glues. The raw materials either came from boiling animal bones, hide, and other offal, or from natural exudates of plants, and these came to be used as the binder for paints. Being ancient in origin, different combinations of binder, pigment, and other substances developed, and those have left a confusion of terms, including glue tempera, and distemper. These represent a spectrum of paints, ranging from those using only glue and pigment, to others also incorporating substantial amounts of powdered chalk or lime to increase their opacity, and related to whitewash.

Glue tempera was used in antiquity, and outside Europe remains in widespread use. It has several disadvantages for the painter, including:

• ‘Drying light’; as the paint dries, so it undergoes marked colour change, reducing the intensity of chroma.
• Mechanical fragility of the paint layer, which is particularly susceptible to abrasion and/or cracking.
• Solution on re-wetting, so that glue tempera can easily be reworked like watercolour, but is unsuitable for exposure to water or damp. Hardening of the glue binder isn’t the result of a stable polymerisation as with oil paints, and can readily be reversed.
• Relatively poor protection of light-sensitive pigments, resulting in some fading over time.

Taken together these mean that what we see in glue tempera paintings today is often quite different from how they looked at the time they were painted.

In the early Renaissance, some artists used glue tempera extensively and with great success, although surviving works haven’t aged as well as those painted using egg tempera or oils.

Dieric Bouts’ The Entombment from about 1450 was painted using glue tempera on linen. As it’s now well over half a millennium old its colours have faded, but it remains worth seeking out when you next visit The National Gallery in London.

In the south of Europe, Andrea Mantegna was one of its great exponents, as shown in his marvellous glue tempera and gold painting of A Sibyl and a Prophet from about 1495. Because this is monochrome and uses gold as the pigment, this has neither changed colour nor faded.

Some artists, such as Joris Hoefnagel, continued to use these ancient techniques, as shown in this painting of Diana and Actaeon from 1597. This is finely executed in glue tempera and gold on vellum, and its colours have survived well.

With the widespread adoption of oil paint, glue tempera almost disappeared until it was revived at the end of the eighteenth century by William Blake.

Blake painted a series of major works in what he termed tempera, using glue as their binder. This Adoration of the Kings from 1799 shows the dulling of colour and fine cracking from his use of stretched canvas as its support.

Some of Blake’s glue tempera paintings have survived in better condition: The Christ Child Asleep on the Cross, or Our Lady Adoring the Infant Jesus Asleep on the Cross from 1799-1800 has fared better, retaining more of its original colour.

Paintings such as Blake’s Virgin and Child in Egypt from 1810 show the fine modelling he was able to achieve in its figures. Overall, though, the condition of his glue tempera paintings isn’t good. It has been suggested that some of their variation is attributable to different sources of glue, clearly of major importance. For a long time, glues provided for this and similar purposes in painting have been referred to as rabbit skin glue, but in reality the great majority have been derived from a wide range of animal products, often in uncontrolled conditions.

After Blake, the medium fell back into obscurity until later in the nineteenth century, when it was revived by movements attempting to return to techniques of the past, most prominently the Nabis in France.

Pierre Bonnard used glue tempera early in his career, when painting this exquisite three-panelled Japoniste screen of The Stork and Four Frogs in about 1889, as the Nabis were forming. Using more modern pigments, Bonnard has achieved high chroma, comparable to anything in oils, and quite unlike traditional glue tempera.

Odilon Redon experimented with glue tempera in his painting of Buddha from 1904.

Édouard Vuillard used glue tempera in many of his paintings both during his Nabi period and later, for example in this view Under the Trees of the Red House from about 1905.

Vuillard’s At The Pavillons in Cricqueboeuf. In Front of the House, from 1911, shows how effective the medium can be.

Vuillard continued to use glue tempera in his late realist paintings, such as Morning Concert, Place Vintimille from 1937-38, showing a trio of friends playing for the artist in his Paris apartment.

Glue tempera remains in use today by a very few artists, who at least have a wider range of lightfast pigments to choose from, and more consistent formulations of glue to act as binder.

In the last few months I have had reports from several whose Macs have experienced a “SEP Panic” rather than a regular kernel panic. Although the immediate effects are the same, and my previous advice on how to deal with a kernel panic still applies, this article looks in more detail at what should be exceedingly rare events.

Essentials

If your Mac restarts or shuts down spontaneously, or ‘freezes’ for you to force it to shut down, chances are that was a kernel panic. When it starts up again, look out for the dialog inviting you to send a report to Apple. Expand that so you can see the panic log, copy and paste that into a text document, and save it. That’s the only record you have of that report, and that provides valuable clues as to what went wrong and how you might go about fixing it.

Apple will not contact you in response to sending the panic log. If you want advice or assistance about your Mac, contact Apple Support, and ensure you have your copy of the panic log ready, as they’ll need to see it.

Secure enclave

No matter how secure you try to make an operating system, if its most precious secrets are being processed by the main CPU cores, an attacker will find a way to access them. The proven solution to this is to build in a separate part of the chip with its own processor, and isolate that from everything else – a secure enclave, with its own secure enclave processor, SEP, as patented by Apple 13 years ago.

Two Mac architectures have secure enclaves and SEPs: Intel Macs with T2 (and T1) chips, where the SEP is in the T2/T1, and Apple silicon Macs, where the SEP is an integral part of the chip. These handle several different security features, including biometrics in Touch ID, management of secure encryption keys including those for FileVault, and performing encryption and decryption for the internal SSD.

The SEP runs its own operating system, sepOS, thought to be a derivative of L4, and communicates with the rest of the chip using mailboxes. When the CPU needs something from the SEP, it posts a message in the SEP mailbox, then retrieves the response when the SEP has processed that request.

What could possibly go wrong?

Like all processors, the SEP can hit problems that it can only manage by a reset, and those will result in it panicking, which in turn provokes the kernel running on the CPU to panic. Those problems can result from anything from a hardware fault to a bug in sepOS.

The SEP in a T2 chip is also known to be vulnerable to some exploits including blackbird, which can be used to ‘jailbreak’ a device using checkra1n or with malicious intent.

Reading the SEP panic log

When a kernel panic is the result of a SEP panic, the panic log is different from normal, and contains considerable detail about the SEP and what went wrong with it. As usual, though, much of that information is cryptic to say the least.

The first line in the panic log confirms that the panic originated in the SEP
panic(cpu 1 caller 0xfffffe001f55e344): SEP Panic: […]

You’re then given the version of sepOS
Root task vers: AppleSEPOS-2772.140.4

Unfortunately, further down it disclaims knowledge of that
Firmware type: UNKNOWN SEPOS

The status of the SEP’s mailboxes are given
Mailbox status:
IDLE_STATUS: 0x00000008
INBOX0_CTRL: 0x00105601
OUTBOX0_CTRL: 0x00023301
and
Mailbox entries:
Unavailable
Mailbox queue pointers: […]

This is confirmed as a panic
Debugger message: panic

The version of macOS is given by build number, with details of the kernel running on the CPU
OS version: 24G90
Kernel version: Darwin Kernel Version 24.6.0: Mon Jul 14 11:30:29 PDT 2025; root:xnu-11417.140.69~1/RELEASE_ARM64_T6000
For a T2 chip, the kernel version given should be for a T8010
root:xnu-11417.140.69~1/RELEASE_ARM64_T8010

Apple silicon Macs should then confirm their iBoot versions, first the LLB (Stage 1) then iBoot Stage 2, and whether Secure Boot was used
iBoot version: iBoot-11881.140.96
iBoot Stage 2 version: iBoot-11881.140.96
secure boot?: YES

T2 SEPs don’t normally give an iBoot Stage 2 version, but provide information about the Intel (x86) host
iBoot Stage 2 version:
secure boot?: YES
roots installed: 0
x86 EFI Boot State: 0xe
x86 System State: 0x0
x86 Power State: 0x0
x86 Shutdown Cause: 0x5
x86 Previous Power Transitions: 0x20002000200
PCIeUp link state: 0x94721611

Information is provided about the task running on the CPU, which should normally be the kernel
Panicked task 0xfffffe1fb0037248: 0 pages, 654 threads: pid 0: kernel_task

Towards the end of the panic log are details about kernel extensions. In SEP panics, that includes the SEP Manager
Kernel Extensions in backtrace:
com.apple.driver.AppleSEPManager(1.0.1)[UUID]@0xfffffe001f5366e0->0xfffffe001f566a63
and
last started kext at 242997189818: com.apple.iokit.SCSITaskUserClient 500.120.2 (addr 0xfffffe001ce0f6a0, size 2206)
loaded kexts:
In the list of loaded kernel extensions that follows, ensure there are no third-party entries, unless your Mac is expected to load them.

Actions

Although you should take a SEP panic seriously, there’s no need to panic yourself. This doesn’t mean that your Mac’s SEP has died, has been attacked by malware, or has released all the secrets it protects. A single panic in isolation could well just be chance, and not indicative of anything serious.

Provided that your Mac starts up correctly and then runs normally, your only essential task is to ensure that you capture and keep a copy of the panic log. If you wish, you can run hardware Diagnostics, but I doubt whether that performs any specific test intended to detect problems in the SEP. If you have potentially problematic peripherals, or any third-party kernel extensions, then you should take the hint and try to eliminate them.

If your Mac suffers any further kernel panics, capture their panic logs, and contact Apple Support with those to hand. Alternatively, book your Mac into an Apple store or authorised service provider for them to check it out for you.

Summary

• SEP panics are exceedingly rare, but are readily identified from the first line of the panic log.
• Ensure you copy and save a copy of the panic log.
• Much of the panic log will appear meaningless, but there is some information about version numbers and kernel extensions that may be helpful.
• Follow the normal recommendations, considering hardware diagnostics, and updating/removing potentially troublesome peripherals and third-party kernel extensions.
• If there are any further panics, capture those and obtain support from Apple.

References

How to deal with a kernel panic (this blog)
Apple, Platform Security Guide
Manu Gulati, Michael J Smith and Shu-Yi Yu, US Patent 8,832,465 B2, Security enclave processor for a system on a chip, filed 25 September 2012, granted 9 September 2014.
Tarjei Mandt, Mathew Soling and David Wang (2016), Demystifying the Secure Enclave Processor, Black Hat USA 16 (PDF)
Blackbird SEP exploit, Apple Wiki.

I’m very grateful to Joe, Marc and another for sharing their SEP panic logs.

After hearing Francesca’s story in the Second Circle of Hell, for those guilty of the sin of lust, Dante weeps for her and faints. When he comes to, he realises that he has already descended to the Third Circle, where it’s pouring with rain, with snow and huge hailstones falling down in sheets. This soaks the ground, turning it into stinking mud.

He sees Cerberus, the fearsome three-headed canine monster that guards this circle, also soaked by the unceasing rain.

Agostino Carracci’s portrait of Pluto from 1592 shows Cerberus alongside his master, and the god holding the key to his kingdom.

Its heads bare their fangs at Dante, but his guide Virgil scoops up three handfuls of mud and throws them into the mouths of Cerberus to assuage its hunger.

Dante and Virgil walk on the flat plain among the prostrate forms of the gluttons. One of them sits up and accosts Dante, reminding him that they knew one another. He is Ciacco (a nickname, literally ‘Hoggio’), who tells Dante of his suffering there, and the names of five other Florentines of noble rank who are to be found in the lower circles of Hell.

Ciacco then falls flat on his face in the stinking mud to await the Final Judgement.

As Virgil leads Dante down to the next circle, they talk of what will happen when the Apocalypse comes, until they reach the dreaded figure of Plutus.

Cerberus is a good example of the redeployment of pre-Christian mythology into Christian beliefs: it was originally the guardian of the Underworld, as depicted by Carracci, and prevented those within from escaping back to the earthly world. It even features in the twelve labours of Hercules, in which he captured Cerberus. With Virgil’s explicit involvement, Dante here incorporates it into his Christian concepts of the afterlife.

The artists

Giuseppe Arcimboldo (1527–1593) was a highly original and individualistic Italian painter now best known for his portraits consisting of assemblies of fruit, vegetables and other objects to form human images. He also painted more conventional works which are largely forgotten today, and was court painter to the Habsburgs in Vienna and Prague. You can see some of his portraits in this article.

William Blake (1757–1827) was a British visionary painter and illustrator whose last and incomplete work was an illustrated edition of the Divine Comedy for the painter John Linnell. Most of his works shown in this series were created for that, although he did draw and paint scenes during his earlier career. I have a major series on his work here.

Agostino Carracci (1557-1602) was one of the Carracci trio, the others being his brother Annibale and cousin Ludovico, who were largely responsible for the reputation of the School of Bologna in Italy. After working as an engraver, he painted a series of major frescos showing the story of Jason and Medea, and the early history of Rome.

Gustave Doré (1832–1883) was the leading French illustrator of the nineteenth century, whose paintings are still relatively unknown. Early in his career, he produced a complete set of seventy illustrations for translations of the Inferno, first published in 1857 and still in use. These were followed in 1867 by more illustrations for Purgatorio and Paradiso. This article looks at his paintings.

John Flaxman (1755–1826) was a British sculptor and draughtsman who occasionally painted. When he was in Rome between 1787-91, he produced drawings for book illustrations, including a set of 111 for an edition of The Divine Comedy. In 1810, he was appointed the Professor of Sculpture to the Royal Academy in London, and in 1817 made drawings to illustrate Hesiod, which were engraved by William Blake.

Joseph Anton Koch (1768-1839) was an Austrian landscape painter, who worked mainly in Neoclassical style. During his second stay in Rome, he was commissioned to paint frescos in the Villa Massimi on the walls of the Dante Room there, which remain one of the most florid visual accounts of Dante’s Inferno. He completed those between 1824-29.

Philippe Semeria is a young contemporary artist who is an enthusiast for comics and is an aspiring illustrator.

Jan van der Straet, also commonly known by his Italianised name of Giovanni Stradano (1523-1605), was a painter who started his career in Bruges and Antwerp in Belgium, but moved to Florence in 1550, where he worked for the remainder of his life. Mannerist in style, he worked with printmakers in Antwerp to produce collections of prints, including an extensive set for The Divine Comedy.

References

Wikipedia
Danteworlds

Robin Kirkpatrick (trans) (2012) Dante, The Divine Comedy, Inferno, Purgatorio, Paradiso, Penguin Classics. ISBN 978 0 141 19749 4.
Richard Lansing (ed) (2000) The Dante Encyclopedia, Routledge. ISBN 978 0 415 87611 7.
Guy P Raffa (2009) The Complete Danteworlds, A Reader’s Guide to the Divine Comedy, Chicago UP. ISBN 978 0 2267 0270 4.
Prue Shaw (2014) Reading Dante, From Here to Eternity, Liveright. ISBN 978 1 63149 006 4.

I hope that you enjoyed Saturday’s Mac Riddles, episode 322. Here are my solutions to them.

1: It’s about evolution, and open source for 25 years.

2: If the kernel isn’t Unix, this is it.

3: Mud puddles in Pittsburgh misheard as the basis for 2.

The common factor

I look forward to your putting alternative cases.

As promised, this new version of my Spotlight indexing and search utility SpotTest extends its reach beyond the user’s Home folder, and can now test and search any regular volume that’s connected to your Mac and mounted in /Volumes.

By default, its searches remain restricted to the user’s Home folder, where SpotTest’s folder of crafted test files is installed. That applies whether you opt to use the search using its NSMetadataQuery tool, or the much faster option of the mdfind tool instead. If you want to search another mounted volume, click on the button for the app to check which volumes are available, then select one from its new Scope menu items. Volumes listed there exclude Time Machine backups and any hidden volumes whose names start with a dot, which will in any case be excluded from Spotlight indexing as they’re hidden.

This new version also fixes a weird bug that you’re unlikely to encounter in the previous version, but in rare circumstances could be infuriating. When searching using the NSMetadataQuery tool, if you had two windows open both with results from that tool, both would be updated with the same search results, and the time taken in them could rise to the absurd. This occurred because both windows were being updated with the data returned from the most recent search, as the NSMetadataQuery is shared in the app’s MainActor. After some fraught debugging, windows in this version ignore any search result updates initiated by other windows. I hope!

Volumes set in the Scope menu only affect search scope. Test folders are created in and removed from the user’s Home folder, and mdimporters are checked there as well. If you want to investigate indexing and search performance on other volumes, then you should manually create your own test folders as necessary. One quick and simple approach is to create a standard test folder in the Home folder, and copy that onto the volume(s) you want to test. A little later this week I’ll illustrate this in an article explaining how to get the best out of SpotTest and how it can help diagnose Spotlight problems.

I have taken the opportunity to improve SpotTest’s reporting of errors, such as trying to remove a test folder that doesn’t exist. I have also thoroughly revised the Help book, and added a page about search scopes.

SpotTest version 1.1 for macOS 14.6 and later, including Tahoe, is now available from here: spottest11
from Downloads above, and from its Product Page.

Enjoy!

Once the ripe grain had been cut, the crop had to be gathered into sheaves, then those were assembled into stooks for transport by cart to await threshing, mechanical separation of the precious grain from straw. The latter was an important building material, and was used as thatch for the roof of most country buildings across Europe.

Anna Ancher, wife of Danish painter Michael Ancher, caught this procession of Harvesters on their way to their work in 1905, near her home in Skagen on the north tip of Jylland (Jutland). The leader carries his scythe high as they pass through a field of ripe wheat.

Léon Augustin Lhermitte’s famous Harvesters’ Pay from 1882 shows four harvesters bearing their heavy-duty scythes, at the end of the day. They are awaiting payment by the farmer’s factor, who holds a bag of coins for the purpose. In the right foreground are two tied sheaves of cut wheat, with a lightweight sickle resting on them.

Adrian Stokes had further to travel for this golden view of Harvest Time in Transylvania (c 1909), one of many paintings that he and his wife made of their protracted visits to Eastern Europe.

By tradition on Norwegian farms, cut cereal wasn’t left to dry in low stooks, as in most of Europe and America, but built onto poles. In a series of paintings and prints, Nikolai Astrup developed these Corn Stooks (1920) into ghostly armies standing on parade in the fields, the rugged hills behind enhancing their strangeness.

John Linnell’s Harvest Home, Sunset: The Last Load (1853) shows the final wagonload of cut grain leaving the fields at dusk, as the harvest is completed.

Félix Vallotton’s The Sheaves from 1915 is one of his moving and symbolic images of the Great War. It’s late summer in 1914, harvest time, and the ripe corn is being cut and stacked in sheaves. But where are all those farmworkers, whose rakes rest against the sheaves, and whose lunch-basket sits on the ground ready to be eaten? Where is the wagon collecting the harvest, and why is the white gate in the distance closed?

In PS Krøyer’s Threshing in the Abruzzi from 1890, teams of oxen are trampling the crop to thresh it.

Jean-Léon Gérôme’s The Grain Threshers, Egypt (1859) also shows this as one of the more traditional employments for animals, here drawing a threshing sledge.

By the end of the nineteenth century, animals were being used as a source of power, as shown in Albert Rigolot’s painting of The Threshing Machine, Loiret from 1893. One of the early uses for steam engines was to power similar machines before they were made mobile under their own power, as traction engines.

As we near the end of Tahoe’s incubation period, and Apple’s engineers code its last fixes and tweaks ready for its launch in just a few weeks, I’d like to reflect on what macOS 26 has to offer beyond its marketing headlines.

While there are several worthwhile new features such as the Phone app, Magnifier, and live translation, there’s nothing to compare with the fundamental changes in recent versions of macOS that brought the SSV, Shortcuts, System Settings and Apple Intelligence. Instead Tahoe is overwhelmingly about its human interface.

Every new design of the Mac’s operating systems that I can recall has elicited outcry from many. Understandably, the majority almost invariably want constancy, the same Finder and app icons that we’ve become so familiar with. It’s only human. It’s also a sure route to what others will condemn as stale, as it hasn’t been refreshed for so many years.

Personally, I don’t like to see a design on my Mac. If I notice it, then it’s a distraction. I’d much prefer to have an interface as clean as the whistles of the late Classic Mac OS period: lean, purposeful and lacking in visual trickery or frippery. But I accept that, without all the adornments and animations, many today would wonder why their Mac needed a GPU. I confess that I was never a fan of the original Aqua interface either. Given that its declared goal was to “incorporate colour, depth, translucence, and complex textures into a visually appealing interface”, I wonder whether much the same could be said of Tahoe.

Perhaps the most striking feature of this redesign is its lack of contrast between elements and tools in window controls and their contents, whether its appearance is set to light or dark mode, or one of its new in-between variants. You can see this clearly in most screenshots of Tahoe, such as those posted by Apple, and as far as I can see it hasn’t improved during beta-testing. This is also universal, and isn’t confined to apps using the more novel SwiftUI, although I have to keep pinching my thigh to remind myself that SwiftUI is now six years old, only two years younger than APFS. The contrast in stability and maturity between the two couldn’t be greater.

You can of course ‘improve’ contrast by enabling Reduce Transparency in Accessibility settings, but in doing so you lose most if not all of Tahoe’s Liquid Glass effects, as they depend on the transparency you’ve just turned off.

Transparency is a good example of design being given priority over readability or content. Because the appearance of the upper layer containing controls or content depends on what is underneath, it’s down to chance whether the greyed text you’re struggling to read happens to be over a background that further reduces its contrast. In the worst case, you could find yourself having to move a window so you can read part of it clearly, not a sign of a good human interface.

My other major concern with Tahoe’s new look is that it seems not to recognise the differences between Macs, iPads and iPhones, in terms of displays, input controls, and apps. Rather than sameness, I’d much rather have consistency that recognises the difference between manipulating Xcode’s compound windows containing dense structured text on a 27-inch display, and checking a family photo filling the 6.1-inch display of an iPhone.

One of my favourite controls in macOS is the Combo Box, a versatile and elegant hybrid of the popup/dropdown/pulldown menu/button and a text entry box. I can’t recall seeing one used in iOS, as it would be clumsy and inappropriate. It’s well supported for macOS in AppKit but hasn’t yet been implemented in SwiftUI. If controls are going to be common across all Apple’s operating systems, then macOS is about to lose one of its best.

It seemed only appropriate that, in the weeks before Apple releases OS 26 across Macs and devices, Tim Cook should go to the White House to pay its corporate tribute in a block of materialised Liquid Glass mounted on pure bling. But the image that I keep thinking of in fear, is that of Elon Musk demonstrating the resilience of his Cybertruck’s window by throwing a metal ball at it, in November 2019. I just hope Tahoe’s Liquid Glass doesn’t go the same way.

This is the time of year when, in the Northern Hemisphere, the grain harvest is in full swing, when the fields of cereal crops have ripened gold in the summer sun and are ready to be cut. This weekend I celebrate the climax of the farming year with some of the finest paintings of harvest in European art. Today I concentrate on cutting using a reaping hook or scythe, and tomorrow I look at the formation of sheaves and stocks, and threshing to separate the grain.

In the centuries before mechanical harvesting, cutting the crop was hard work and labour-intensive. It took about 4 worker-days to cut an acre of grain using a sickle or hook, while using a scythe typically took only 2 sweated worker-days per acre. Scythes appear to have been used almost exclusively by men, while sickles and hooks were used by both men and women.

Pieter Brueghel the Elder’s Harvesters from 1565 shows the whole village turned out to cut, process and transport the crop. This is a visual encyclopaedia of each of the steps involved in the grain harvest, as shown in the details below.

These men are cutting a crop of wheat close to the base of the stem using scythes, leaving short stubble. This ensures the best yield of straw as well as grain.

Behind these workers eating bread baked from flour ground from cereal grown in the same fields, cut cereal is tied first into sheaves before they are gathered into stooks.

In about 1833, when Samuel Palmer painted his wonderful Harvest Moon near Shoreham in Kent, harvesting usually went on well into the night. These are mostly women wielding sickles or reaping hooks to cut a small field of wheat. The cut stalks are then formed into stooks and piled onto an oxcart for transport to nearby farm buildings.

Palmer’s mentor John Linnell painted The Harvest Cradle twenty-five years later, in 1859. The harvesters have their backs to the viewer, but appear to be using scythes to cut this wheat crop. Bundles of cut grain are tied as sheaves, then assembled into stooks in the foreground.

He painted Wheat for the dealer Thomas Agnew in about 1860, and it became one of Linnell’s more successful works. It was shown at the Royal Academy shortly after completion, then at the Exposition Universelle in Paris in 1867.

Jean-François Millet’s Ceres (The Summer) from about 1864-65 is unusual in showing the goddess holding a sickle with a serrated edge, surrounded by sheaves of wheat. On her left she holds a shallow winnow used to separate the lighter chaff from the heavier grain, after threshing.

During the nineteenth century some attached cradles to the blade, to make sheaving easier. This is shown in Laurits Andersen Ring’s painting of Harvest. The crop being cut here may well be rye rather than wheat. The artist got his brother to model for this “monument to the Danish peasant” during the summer of 1885, while working on his farm near Fakse, on Sjælland (Zealand), Denmark.

Volodymyr Orlovsky’s Harvest in Ukraine from 1880 shows wheat being cut on the steppe, with the worker in the foreground carrying a scythe, but those cutting in the middle distance bent over as if using hooks instead.

The young woman in Mykola Pymonenko’s portrait of a Reaper from 1889 has been cutting what could be rye or wheat using a heavier bagging hook, although she isn’t using the hooked stick normally required for the technique, so could be using it as a regular reaping hook. The woman behind her demonstrates that these harvesters are cutting low to keep a good length of straw on the harvested crop.

Here are this weekend’s Mac riddles to entertain you through family time, shopping and recreation.

1: It’s about evolution, and open source for 25 years.

2: If the kernel isn’t Unix, this is it.

3: Mud puddles in Pittsburgh misheard as the basis for 2.

To help you cross-check your solutions, or confuse you further, there’s a common factor between them.

I’ll post my solutions first thing on Monday morning.

Please don’t post your solutions as comments here: it spoils it for others.

When Mac OS X 10.0 was released in March 2001, privileges, permissions and security adopted a conventional model based on BSD and Unix. Those sufficed for 15 years until the release of OS X 10.11 El Capitan in September 2015, when System Integrity Protection, SIP, was introduced. This article outlines its history over the last decade.

2015 Introduction

The first public account of SIP was presented by Pierre-Olivier Martel at WWDC 2015 in June, and documented in Apple’s System Integrity Protection Guide that September, which hasn’t been revised since. These changes were justified as adding a further layer of security protection to prevent attackers from gaining full control by escalating privileges to root.

Three types of protection were promised:

• file system protections, so that system files could only be modified by processes signed by Apple;
• prevention of runtime attachment, code injection, or modification of system binaries, with modifications only permitted by Apple’s installers and updaters;
• kernel extensions (kexts) had to be signed using special certificates granted by Apple.

Each Mac’s SIP configuration was stored in NVRAM, and controlled by the csrutil command used in Recovery mode.

When released, the csrutil command provided some degree of separate control over six groups of features: file system protections, debugging protection, DTrace protection, kext signing requirement, NVRAM and ‘Apple internal’ protection. One immediate beneficial side-effect was that SIP prevented permissions being changed for system files, and that made the practice of repairing permissions on them unnecessary, allowing removal of support for that procedure from Disk Utility.

2015 Conflicts

Press reviews of the SIP feature were divided, with some claiming it was a sign that OS X was being closed down and moved to the iOS security model, while others considered that few users would notice much difference.

Problems resulting from SIP were reported soon after El Capitan’s release. For example, some older Mac models intentionally prevented their use with Apple USB SuperDrives. One workaround to address that had been to modify one of the files now protected by SIP, which consequently required the user to disable SIP to make that change.

As kernel extensions hadn’t previously been required to be signed at all, other early casualties were all older unsigned kexts, making some apps unusable unless a new version was provided with a correctly signed kext.

2016 Error

Late in 2016, it became clear that Apple had shipped a substantial batch of new MacBook Pro systems with SIP disabled. At that time, System Information was unable to report SIP status, and the only way to enable protection was to start that Mac up in Recovery mode and use the csrutil command in the Terminal app there. That applied to macOS Sierra 10.12 to 10.12.1.

To make this easier, Apple changed csrutil so that it could enable SIP when invoked in normal running mode, provided it was run with elevated privileges obtained using sudo. Despite that, some of those affected MacBook Pro models didn’t have SIP enabled correctly for several months.

2017-18 Problems

Over the following years, SIP continued to cause irritations that infuriated some users.

Bundled apps in the main Applications folder were protected by SIP, and that prevented the user from modifying them. As the handling of kexts changed, it was discovered that SIP made it awkward to remove old kexts the user had installed. That was because the folder /Library/StagedExtensions was put under the protection of SIP by attaching a com.apple.rootless extended attribute to it.

One reading of that extended attribute is that only Apple’s KernelExtensionManagement service can give permission for changes to be made within that folder, and the folders within it.

2020 Extended attributes

Apple later used SIP to lock down individual extended attributes (xattrs) attached to regular unprotected files. The first example of this was the undocumented com.apple.macl xattr that macOS started to attach widely to all user documents. Presence of that xattr was implicated in some problems in which those documents became locked down and unable to save changes, despite permissions and other visible attributes showing that the user had full ownership of the file. The only workaround for this has been to copy the file to another volume, where the xattr no longer has the protection of SIP, and can be stripped.

When Apple later introduced another undocumented xattr com.apple.provenance, that too was sometimes but not always protected by SIP, although that hasn’t been implicated in problems visible to the user.

2022 Launch constraints

Launch constraints were introduced in macOS 13 Ventura and iOS 16 in 2022. Every executable binary in the system now has a set of rules determining the requirements for that binary to be launched. These include self constraints that the binary itself must meet, parent constraints that must be met by its parent process, and responsible constraints that must be met by the process requesting the launch. Together these form that code’s launch constraints. To make those constraints simpler, they come in different categories, ranging from 0, in which there are no constraints at all, to combinations that prevent launch by processes that aren’t themselves part of the system and require the code itself to be on the System volume.

Although Apple has documented these for developers, they can cause unexpected behaviour for users, who haven’t been given any explanation. Testing has demonstrated that launch constraints are dependent on SIP, so must be assumed to have been added to its list of protections.

2024 Malware scans

Many users have reported slowing app launch times in recent versions of macOS. In February 2024, Jeff Johnson investigated these, and concluded that the cause was the macOS security system repeatedly performed malware scans against a growing set of Yara rules. These stopped when SIP was disabled, implying that this is yet another protection that has been added to those controlled by SIP.

2024 Current protections

Current user documentation for SIP explains only its file system protection, csrutil‘s man page refers to its usage information, but from that and XNU it’s possible to separate out its controls to include the following, at least:

• Filesystem Protections, disabled by CSR_ALLOW_UNRESTRICTED_FS, abbreviated to fs
• Debugging Restrictions, disabled by CSR_ALLOW_KERNEL_DEBUGGER and CSR_ALLOW_TASK_FOR_PID, abbreviated to debug
• DTrace Restrictions, disabled by CSR_ALLOW_UNRESTRICTED_DTRACE, abbreviated to dtrace
• Kext Signing, disabled by CSR_ALLOW_UNAPPROVED_KEXTS, abbreviated in csrutil to kext
• NVRAM Protections, disabled by CSR_ALLOW_UNRESTRICTED_NVRAM, abbreviated to nvram
• Apple Internal, disabled in XNU by CSR_ALLOW_APPLE_INTERNAL, and only disabled when SIP is fully disabled
• BaseSystem Verification, abbreviated to basesystem
• Boot-arg Restrictions, disabled with nvram
• Kernel Integrity Protections, disabled with kext
• Authenticated Root Requirement, disabled by CSR_ALLOW_UNAUTHENTICATED_ROOT, managed separately using csrutil authenticated-root disable and enable
• Additional configuration flags available in XNU that don’t appear to be directly supported by csrutil include: CSR_ALLOW_TASK_FOR_PID, CSR_ALLOW_DEVICE_CONFIGURATION, CSR_ALLOW_ANY_RECOVERY_OS and CSR_ALLOW_EXECUTABLE_POLICY_OVERRIDE. Those should be disabled when SIP is fully disabled.

2015-2025 Vulnerabilities

Over the last decade, many vulnerabilities have been discovered in SIP that have allowed parts of its protections to be bypassed. Among the most recent is CVE-2024-44243 discovered by Jonathan Bar Or (@yo_yo_yo_jbo) of Microsoft Threat Intelligence and Mickey Jin (@patch1t), and fixed in the update to macOS 15.2 Sequoia. However, this wasn’t fixed in Sonoma until the following round of updates (14.7.3), and appears to remain unpatched in Ventura 13.7.8.

Microsoft’s report explains how bypassing just one of SIP’s many protections can give access to bypasses of more or all of SIP’s other protections. Note also how Apple’s description of the vulnerability in its security release notes refers to StorageKit but doesn’t reveal that this affected SIP.

Over the last decade, SIP has grown like Topsy from three protections that seemed worthwhile and simple, into a protean collection of many parts that remain largely undocumented and pervade much of modern macOS security.

References

Wikipedia’s account, still largely based on SIP in 2015
This blog on csrutil controls

Lovis Corinth wasn’t the only artist to have his own suit of armour. Rembrandt apparently bought at least one, while Jean-Léon Gérôme seems to have kept a suit hanging in his studio.

The End of the Pose (1886) is the first of Gérôme’s series of unusual compound paintings, which are at once self-portraits of him as a sculptor, studies in the relationship between a model and their sculpted double, and further forays into issues of what is seen, visual revelation, and truth.

Here, while Gérôme cleans up, his model is seen covering up her sculpted double with sheets, as she remains naked. Hanging against the wall behind is a complete suit of armour, and there is a single red rose on the wooden platform on which the model and statue stand.

Armour has occasionally been purely symbolic, most famously in the collaborative painting of Touch by Jan Brueghel the Elder and Peter Paul Rubens in their series The Five Senses from 1618.

Touch extends beyond its title to encompass other tactile sensory modalities. Heat is associated with a brazier, fine touch with brushes nearby. Much of the panel is devoted to a collection of armour, weapons, and their manufacture by gunsmiths and armourers. The many suits on display, seen in the detail below, appear to be equipment that isolates rather than stimulates the sense of touch.

During the nineteenth century, many painters looked back at the age of knights and chivalry, which inspired German Romantics, Pre-Raphaelites, and some of the last academic artists of the century.

The crusades presented Carl Friedrich Lessing with an ideal combination of mediaeval history, romance, and chivalry. In The Return of the Crusader from 1835, he shows a lone knight in full armour dozing as his horse plods its way up a path from the coast. Although his armour is still shiny, a tattered battle pennant hangs limply from his lance. This is based on a Romantic poem by the writer Karl Leberecht Immermann (1796-1840).

Edmund Blair Leighton’s Conquest from 1884 shows a stereotype knight in shining armour walking through an arch with its portcullis raised, a fair maiden walking behind him, as this victor enters the castle he has just conquered. The knight appears to be an idealised self-portrait.

Leighton’s The Accolade (1901) apparently shows Henry VI the Good – of Poland, not the British Henry VI – being dubbed a knight. Every link in his chain mail has been crafted individually.

Manuel García Hispaleto’s Don Quixote’s Speech of Arms and Letters (1884) shows the hero, his squire Sancho Panza behind, delivering one of his many orations after dinner, in a full suit of armour, as you would.

Eugène Delacroix visited tales of chivalry in his Combat Between Two Horsemen in Armour, painted at some time between 1825-30.

Plate armour continued to be worn by soldiers well into the twentieth century, and appears in some paintings of contemporary history.

Paul-Émile Boutigny’s undated Scene from the Franco-Prussian War shows soldiers from both sides of this short war in 1870-71. The soldier on the left is French, and holds a French Chassepot musketon with a long yataghan bayonet, while his colleague on the right appears to be Prussian, with his pickelhaube spiked helmet and a heavy cavalry cuirass that’s essentially modernised armour. (I’m grateful to Boris for his expert interpretation of this motif.)

François Flameng’s undated scene of Germans from the First World War shows the odd combination of archaic plate armour with modern gas masks.

Finally, as everyone knows, a knight goes to their grave in their armour.

Briton Rivière’s Requiescat from 1888 epitomises the faithful relationship between a dog and its master. As the knight’s body is laid out clad in armour, so his dog sits pining by the side of his body.

Sometimes even the best-kept Macs start acting strangely, and no matter what you try, you can’t put your finger on the problem, and can’t make it go away. This article suggests some potentially radical solutions that should address the most intransigent of problems in Apple silicon Macs.

Hardware?

If the problem lies in a peripheral, or the Mac’s hardware, then everything else is doomed to fail. Start by disconnecting all non-essential peripherals, and if that doesn’t help, run hardware diagnostics from Recovery mode. Those don’t always catch problems, particularly in their early stages, so if you’re not convinced that your Mac is sound and healthy, book it in for your nearest Apple store or authorised service provider to run their more extensive tests.

To run hardware diagnostics in an Apple silicon Mac, start it up in Recovery by pressing its Power button until it displays that it’s loading options, then in the initial Options screen, hold Command-D until the Diagnostics Loader starts. This may require download of the disk image from Apple’s servers before testing can proceed, so a good Wi-Fi connection is important. Once loaded, there’s a hidden option for extended diagnostics that can be triggered by holding the Command-E key combination.

What to reinstall?

At this stage with an Intel Mac, you’d be considering performing a clean reinstall of macOS, maybe even trying to revert to an older version that didn’t show the problem. Although you can still try that in Recovery mode, Apple silicon Macs have a better and more thorough option, to Restore the whole of your Mac’s firmware and macOS. This is performed by putting it into DFU mode, connected to another Mac (either architecture) running a recent version of macOS, and performing the Restore from there.

Apple provides detailed instructions for you to do this yourself, provided you have the necessary second Mac and cable. If you don’t have those, you should be able to get this performed free of charge at an Apple store, or by an authorised service provider.

The cable used mustn’t be Thunderbolt, but plain USB-C. That’s because DFU mode doesn’t support Thunderbolt or its cable. Connect that to the designated DFU port on the Mac you’re going to Restore. That can be found in Apple’s note, or in Mactracker.

You used to have to run Apple Configurator on the second Mac, but this can now be handled through the Finder, where it’s usually the more reliable. Follow Apple’s instructions to Restore the current version of the firmware and macOS, or you can download an IPSW image file for most previous versions through the links on Mr. Macintosh’s site.

Before performing this, you must make a full backup of your Mac’s internal storage, as the Restore process wipes it clean, and you’ll want to restore from that backup afterwards. As this process is going to wipe your Mac, you’ll also want to check through third-party apps and subscriptions that need to be signed out or transferred. Check carefully through the Applications folder to ensure that you haven’t forgotten any that are still valid. Among those is the need to deauthorise your old Mac for Apple media, something you should do using one of its media apps such as Music or TV.

Revive or Restore?

Apple advises trying to revive your Mac first, as it’s a briefer procedure and doesn’t wipe the whole of the Mac’s internal storage. However, if you’re trying to fix a deep-seated problem, only a full Restore will do.

What does a Restore do?

Internal storage in Apple silicon Macs contains additional partitions/containers to those found in Intel Macs or on external boot disks. These store the firmware and other components used early during the boot process, as part of Secure Boot. A ‘clean’ reinstall only replaces the boot volume group, the Signed System Volume (SSV) and Data volume, while a Restore in DFU mode wipes everything including the firmware, and replaces it with fresh copies from the IPSW file.

The end result is that your Mac is running the firmware to match the version of macOS installed, just as it would have been from the factory. It then has to be personalised and reconfigured from scratch once it’s started up. Nothing from its old firmware, macOS or Data volume is left, even the NVRAM, stored in NOR Flash memory, is reset.

Summary

• Hardware diagnostics in Recovery
• Consider extended diagnostics in Apple store
• Back up and prepare Mac
• Restore in DFU mode, using chosen IPSW if desired
• Restore from backup.