With macOS Tahoe already more than half way through its cycle, and Apple’s WWDC announced, now is a good time to plan your Mac’s calendar. This article peeks at what lies ahead for macOS over the next six months.

Since the pandemic disruption settled, minor version updates to macOS have become more regular. Looking across Sonoma, Sequoia and Tahoe, greatest variation in their timing has been in their x.3 and x.4 releases, that have varied between 22 Jan – 11 Feb, and 7 – 31 March, respectively. x.5 to x.7 have been more consistent, as they’re more tightly constrained by events including WWDC, the subsequent new beta season, and for some maybe even a vacation.

Those are summarised in the chart above, together with my predictions for the dates we should expect the remaining minor versions of Tahoe. Those should bring its cycle to look like:

• 26.0 – 15 September 2025
• 26.1 – 3 November 2025
• 26.2 – 12 December 2025
• 26.3 – 11 February 2026
• 26.4 – 24 March 2026
• 26.5 – 11 May 2026
• 26.6 – 27 July 2026
• 26.7 – 14 September 2026.

Where my forecasts are given in italics. Patch releases, such as 26.3.1, and BSIs occur outside that schedule. While we’re on the topic of BSIs, all indications are that Apple only intends to provide them for the current release of macOS, as it did with RSRs, which means that those Macs staying with Tahoe from 26.7 will no longer get them. It’s unclear how significant a loss that might prove.

WWDC this year is being held between 8-12 June, and will almost certainly bring the first developer beta release of macOS 27.0 (and all Apple’s other OSes). That’s likely to be made available to public beta-testers in early July. This is particularly significant this year, as it will be the first version of macOS to run exclusively on Apple silicon Macs.

For those with Intel Macs, or intending to remain with older versions of macOS, likely dates of release for scheduled security updates to Sonoma and Sequoia are:

• 15.7.6, 14.8.6 – 11 May 2026
• 15.7.7, 14.8.7 – 27 July 2026
• 15.7.8, 14.8.8 – 25 August 2026
• 15.8 – 14 September 2026.

The date at the end of August is possible, but less likely than the previous two. So far this year, security updates for Sonoma and Sequoia have been keeping reasonably close to those for Tahoe, in terms of vulnerabilities addressed, so the security gap between them has been rather less than in previous cycles.

However, the important message here is that it’s unlikely that Sonoma will receive any further security updates after the end of August this year. If your Mac is capable of being upgraded to Sequoia, now is the time to plan that, or it’ll all too quickly be September and your macOS will have lost its last support.

Similarly, if you’ve been holding back from upgrading to Tahoe in the hope that it will undergo interface improvements, I’m afraid that’s now looking increasingly unlikely. If it’s an Intel Mac capable of running Tahoe, there’s little point in avoiding making that decision any longer. There’s only limited time and scope left for improvement in macOS 26, with most engineers now more focussed on getting macOS 27 ready for WWDC.

Key forecasts

• 26.5, 15.7.6, 14.8.6 – 11 May 2026
• 27.0 developer beta – 8 June 2026
• 27.0 public beta – 8 July 2026
• 26.6, 15.7.7, 14.8.7 – 27 July 2026
• 27.0, 26.7, 15.8 – 14 September 2026.

Apple has just released its regular weekly update to XProtect, bringing it to version 5336. As usual it doesn’t release information about what security issues this update might address.

This version adds two new rules for MACOS.WANNABEWALLABY.IMA and MACOS.WANNABEWALLABY.STA, amends rules for MACOS.TIMELYTURTLE.DYHEOC, MACOS.SOMA.MAENA, and MACOS.SOMA.MAENB, and changes some rule UUIDs. In the Osascript rules in XPScripts.yr, it amends the rule for MACOS.OSASCRIPT.SYPR.

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_15-5336

Sequoia and Tahoe systems only

This update hasn’t yet been released for Sequoia and Tahoe 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 5336 but your Mac still reports an older version is installed, you should be able to force the update using
sudo xprotect update

Over the many centuries before photography, the only way that most folk, including artists, could see paintings was by looking at prints or copies made of the originals. This was recognised early by some including Albrecht Dürer, who made woodcuts and engravings to reach a wider public, and some specialised in painting works that would generate additional income from their prints. Among those are some whose skills included both forms of visual art, including William Hogarth, William Frith, Gustave Doré, and later Mary Cassatt and Nikolai Astrup. This article looks at a few examples of their paintings that were turned into prints.

A largely self-taught painter, Hogarth entered the world of art as a copperplate engraver in 1720. He aspired to greater things, and became a pupil at an academy run by Thornhill in London, even marrying Thornhill’s daughter in 1729. His works in oil were usually strongly narrative, showing moments of climax and sometimes peripeteia in theatrical productions or everyday life in London. Many included social commentary, wit, and some overtly caricatured society. One of his reasons for painting was to provide a supply of original images for engraving, and all his series paintings were seen, from a commercial view at least, as a means to producing lucrative series of prints.

Following his successful narrative series of prints Industry and Idleness, Hogarth moralised again over one of his favourite issues: cruelty to animals. Victorian society was even harsher in its attitudes towards animals than it was towards the ‘lower classes’ of humans, and Hogarth saw the two as being linked.

As with Industry and Idleness, Hogarth wanted to reach the hearts of the ordinary people, and to make his prints as affordable as possible. He admitted to simplifying his drawings in order to put his points across as clearly and accessibly as possible. He stated that “neither minute accuracy of design, nor fine engraving, were deemed necessary”. In a further effort to cut costs, he commissioned them to be turned into woodcuts rather than engraved, but in the end only two of the plates were completed in wood, and Hogarth himself created conventional engravings.

This early sketch in pencil and red chalk gives a good idea of his initial concept for the first in this series.

That was progressed to a final drawing in red chalk (above) to be turned into the line engraving below, shown mirrored so that it matches the drawings.

This is the same print as seen by the viewer. Hogarth’s schoolboy Tom Nero is seen, together with many of his peers, in a street in the slum district of St Giles in London. He’s shown in a ragged white coat just below the centre of the image, inserting an arrow into a dog which is plainly in agony. The dog’s owner pleads for mercy, offering Tom a pie, but others help hold the dog for Tom. Just to his left, someone has drawn a hanged man with Tom’s name below, a grim prediction of what is to come.

All around there are vicious acts of cruelty taking place to animals. A cat and dog are fighting, cockfighting is in progress, another dog has a bone tied to its tail, two boys are burning a bird’s eyes out, two cats are suspended by their tails from a vintner’s sign, and a cat has been thrown out of a high window with balloons attached to it.

For some of his series, Hogarth worked up a set of full oil paintings in addition to prints. My example is taken from A Rake’s Progress, painted between 1732-5, the successful successor to his A Harlot’s Progress.

In Hogarth’s oil painting, Tom sets out to make a new man of himself with the aid of many tutors and hangers-on. The composer Handel plays the harpsichord, then there is a fencing master, a quarterstaff instructor, a dancing master with violin, Charles Bridgeman, a famous landscape gardener, Tom himself, an ex-soldier acting as bodyguard, a bugler from a foxhunt, and a jockey. In the background are others who are busy spending Tom’s inheritance on worthy causes no doubt.

The print is different in many respects, as if the artist forked the painting and print from a late sketch. Details on the music being played at the left are different, and there’s a long scroll running down from the back of the chair in the print. Some of the facial expressions are altered and exaggerated in the print. Details, including those of clothing and frames of the paintings on the wall, also differ.

Artists like Edgar Degas and his protégé Mary Cassatt made prints for different reasons.

Towards the end of the nineteenth century, Cassatt made this very loose painting of a mother and daughter feeding ducks from a boat in Summertime (1894). I believe this was the source for the sophisticated print, called more appropriately Feeding the Ducks (c 1894), below.

For this she combined her mature drypoint technique with aquatint, to which she added monotype. In monotype, the artist lays down an image on a plate using printing inks, then makes a single impression of that on the paper. This demands meticulous technique, and usually results in one completed print for each image made in ink. Although second prints can sometimes be made, they’re usually of low quality.

The Norwegian artist Nikolai Astrup was a prolific painter and printmaker, whose paintings informed his prints, and prints informed his paintings.

A Clear Night in June (1905-07), above, and A June Night and Old Jølster Farm (before 1911), below, are two of more than a dozen paintings Astrup made of this farm after about 1902. These were painted early each summer, when in some years there were still the remains of the winter’s snow on the rugged hills behind. The waterfalls cascading down the scarps are still in spate from the melting snow.

Astrup painted this view when the blossom was on the trees, and the meadows were a patchwork of yellow with the first of the summer flowers. Comparing these two paintings reveals a few differences in detail, such as the low fence in the foreground in the lower painting which is omitted in the upper, but by and large Astrup seems to have been consistent, suggesting his paintings were true to nature.

A few years later, he turned those into prints such as this Marsh Marigold Night (c 1915). By this time his printmaking technique had come a long way, and many of his later prints were extremely painterly, to the point where it can be difficult to distinguish his woodcuts from their painted originals.

Reference

Ayrton M & Denvir B (1948) Hogarth’s Drawings, London Life in the 18th Century, Avalon Press. No ISBN. [This has been my source for images of many of the scans above. The book bears no information about copyright, the press has long since vanished as far as I can tell, and I assume ‘fair use’ of these orphaned images. If you know any different, please contact me.]

For those working with Rich Text without embedded images, my free editor DelightEd offers a suite of unique features. I wrote it when macOS Mojave introduced Dark appearance mode, with the primary purpose of composing Rich Text documents that work independent of appearance. For that it can set styled text on a background that ensures perfect readability in both Light and Dark modes.

Since then it has gained other unique features, including support for creating interlinear text, in which different translations or versions of the same document are interleaved line by line. It will also open PDF documents and automatically extract all their text content.

General features supported include Writing Tools (Apple silicon Macs), case transformations, and a full suite of substitutions. However, until this new version of DelightEd, substitution settings haven’t been saved in DelightEd’s app settings. Version 2.5 now puts that right: to set the app’s default substitutions, set them up using the Substitution command in its Edit menu, for instance enabling Smart Links.

Then save those to its settings using the Save Defaults command in the app’s menu. Each time you open DelightEd after that, its substitutions will start from those saved defaults.

DelightEd version 2.5 for macOS 11.5 Big Sur and later, including Tahoe, is now available from here: delighted25
from Downloads above, from its Product Page, and through its auto-update mechanism.

I’m very grateful to Manuel for asking for this to be fixed.

The ‘Saracen’ sorceress Armida had abducted the crusader knight Rinaldo to her enchanted garden on the Fortunate Isles, far to the west out in the Atlantic. A rescue team of the knights Charles and Ubaldo then sailed out in a magic ship piloted by a fair woman. After they had overcome a series of obstacles, Charles and Ubaldo found Rinaldo dressed and behaving as a woman’s dandy, and have the task of restoring his senses as a warrior knight, so they can take him back to rejoin the siege of Jerusalem.

By showing Rinaldo his own image in a highly polished shield, the knight is put to shame and realises what he has become. Ubaldo bids him rejoin the forces of Godfrey of Bouillon, and the holy war. They hasten away, leaving Armida weeping and choking with grief. She runs after them, calling him back. Rinaldo and his two companions wait for her, and the couple stare at one another in silence.

The scene of Armida and Rinaldo separating has proved another of Tasso’s great images for art. Its greatest exponents were the Tiepolos, father and son, who painted a succession of works showing this parting, in the eighteenth century. I show here four examples, each using the compositional device of collapsing Armida’s garden on one side, with the beach and ship on the other, and using that spatial and temporal merging to tell the whole sequence, from Rinaldo’s awakening to their departure by sea.

In this version for the Tasso Room in the palace of the Cormaro Family in Venice, painted in 1742-45, Charles and Ubaldo are stood in full armour, pointing to their ship which is waiting to take Rinaldo away. Armida lies back exposing a lot of leg, trying to persuade Rinaldo to stay with her.

In Tiepolo’s Rinaldo’s Departure from Armida from 1755-60, Rinaldo is still being woken from his enchantment, and Armida bares her breast as she is trying to lure him back.

His son, Giovanni Domenico, squeezed the three knights in tighter, and omitted Armida from his Rinaldo Leaving the Garden of Armida in about 1770. Rinaldo’s separation from Armida is marked by the hold he has over the blindfolded Cupid in his right arm. This was painted in a fresco in Ca’ Rezzonico in Venice, Italy.

The father Tiepolo had painted another variation in Rinaldo Abandoning Armida, from 1757, as a fresco in the Villa Valmarana ai Nani, in Vicenza, Italy. In this, the composition is reversed, with the ship at the left, and Armida pleading with Rinaldo at the right. This is perhaps Tiepolo’s most complete account, as it includes both Armida’s crystal mirror at the right, and the polished shield into which Rinaldo looked, at the feet of Charles and Ubaldo.

Tasso’s narrative, developed in this painting, may have a sub-text about looking and its power: for Armida looking in her crystal was a means of strengthening her allure over Rinaldo, but for him looking into the polished shield was a means of restoring his power by showing what he had become in her clutches.

The Tiepolos were by no means the first to merge Armida’s garden with the sea and ship. Nicolas Colombel’s undated painting from the late 1600s showing Rinaldo Abandoning Armida has done much the same.

Armida then launches into a speech, asking Rinaldo to let her follow him back, and offering to be his shield. His love has been replaced by compassion for her, and he asks her to remain there in peace. The three knights then sail away on the magic ship, leaving Armida behind on the beach. Her grief now changes to anger at her loss, so she casts evil spells and conjures up her chariot. On that she departs for the battlefield in vengeance.

David Teniers the Younger shows this section of the story in two of his small paintings on copper: in his Armida and Rinaldo Separated of 1628-30, Armida is weeping and being comforted by Charles and Ubaldo, as the woman pilot of their ship waits for them to board by its stern.

Teniers’ sequel, Rinaldo Flees from the Fortunate Isles, shows the group returning to war, with Armida still looking disconsolate in her chariot above them.

Canto seventeen opens in Gaza, between Egypt and Jerusalem, where the King of Egypt is mustering his army ready to advance towards Godfrey’s forces. He sits on his throne to review his forces, which Tasso lists in procession much as he had done when the crusaders were setting out for Jerusalem at the start of the epic. These start with Egyptians, and progress through those from the coast of Asia, citizens of Cairo, those from the land to the south, men of Barca, those from the coast of Arabia, from the Persian Gulf, and the Indies. At the end, Armida appears riding in her chariot with her own forces who had been mustered in Syria by Hydrotes, together with Circassians and more.

The king then retires to a banquet, where Armida offers her forces in support of the king, and tells of her desire for vengeance against Rinaldo. Adrastus, a ‘Saracen’ leader of Indian troops, offers to rip Rinaldo’s heart out, and make a present of his head to Armida.

References

Wikipedia on Jerusalem Delivered.
Wikipedia on Torquato Tasso.

Project Gutenberg (free) English translation (Fairfax 1600).

Librivox audiobook of the Fairfax (1600) English translation (free).

Thomas Asbridge (2004) The First Crusade, A New History, Free Press, ISBN 978 0 7432 2084 2.
Anthony M Esolen, translator (2000) Torquato Tasso, Jerusalem Delivered, Gerusalemme Liberata, Johns Hopkins UP. ISBN 978 0 801 863233. A superb modern translation into English verse.
John France (1994) Victory in the East, a Military History of the First Crusade, Cambridge UP. ISBN 978 0 521 589871.
Joanthan Riley-Smith, ed (1995) The Oxford Illustrated History of the Crusades, Oxford UP. ISBN 978 0 192 854285.
Jonathan Riley-Smith (2014) The Crusades, A History, 3rd edn., Bloomsbury. ISBN 978 1 4725 1351 9.
Johathan Unglaub (2006) Poussin and the Poetics of Painting, Pictorial Narrative and the Legacy of Tasso, Cambridge UP. ISBN 978 0 521 833677.

I hope you enjoyed Saturday’s Mac Riddles, episode 353. Here are my solutions to them.

1: The future was here 25 years ago when the fastest land animal arrived.

2: This atelier came with more than a marathon four years ago.

3: Wicked fast at 40 MHz, its special effects impressed 36 years ago.

The common factor

I look forward to your putting alternative cases.

Many discovered how long 5 minutes could last when they updated from macOS 26.3.1 to 26.4. Right at the end of its Preparation phase, Software Update showed there were only 5 minutes remaining for far longer. This article reveals what went wrong with that update.

My observations come from a Mac mini M4 Pro running a vanilla installation of macOS Tahoe, being updated from 26.3.1 (a) with the BSI installed, to 26.4. Times and details are taken from log extracts covering the final 14 minutes of the update, immediately prior to the reboot for its installation.

Preparation

At almost exactly 18:43:00, softwareupdated reported that the PREPARING_UPDATE phase was in progress, with 70% complete on the progress bar, and 20 minutes remaining. Periodic preparation activities were then reported in the log, mainly verifying components to be installed as part of the update. One of the longest of those, /usr/standalone/i386/Firmware.scap, took nearly 6.5 minutes alone, although you might wonder why that’s required on an Apple silicon Mac!

Eleven seconds later, softwareupdated changed the progress bar to display 10 minutes remaining, with 71% completed. Just 1.5 seconds later that changed again to display 5 minutes remaining with 94% complete. Six seconds after that, with 5 minutes still displayed, the log records 98.6% was complete.

The log and progress bar then remained stuck at 5 minutes remaining and 98.6% complete for the next 11 minutes and 47 seconds, before changing to 99.9% complete and no time remaining.

These are plotted in the chart below.

The final 5 minute period started at 18:43:12, and lasted until 18:55:04, as reflected in the long period of 98.6% completion (upper line) and 5 minutes remaining (lower line).

The “5 minutes” remaining actually took 12 minutes and 7 seconds, although log entries make it clear that preparation continued throughout that time, with further verifications and “Preparing system volume…”. Those details were reported as ActionText for progress monitoring, but curiously aren’t accessible to the user at the time.

Log entries record softwareupdated keeping detailed records of progress over this period, though. For example:
18:51:32.924688 softwareupdated PrepareUpdate PROGRESS (Continue) | state:{
ActionText = "Preparing system volume...";
ElapsedTime = 490;
ExpectedTime = 1335505;
PercentBytesComplete = "48.05373989419242";
PercentComplete = "4.701870471432042";
}
But those aren’t reflected in the progress bar.

Once the update had completed that preparation phase, extensive checks were performed to ensure it was correctly configured, and components were moved into place in the ‘stash’ to be used during installation. One second after successful completion, softwareupdated locked the controller state and waited for the reboot to start installation. Rebooting followed less than two minutes later.

What went wrong?

The macOS 26.4 update for Apple silicon Macs was large, and the work required to verify its contents and complete its preparation was incorrectly reported in both percent completion and time remaining. Even in smaller updates, some form of progress needs to be shown in the progress bar during these later stages of preparation, or users may be mislead into thinking the update has frozen or failed, and could for example restart their Mac to try updating again.

What should the user do?

When an update claims there’s only 5 minutes left, that could readily extend to longer, possibly on slower Macs as long as 30 minutes or more. Unless there’s evidence that the update has gone wrong at this stage, you should leave your Mac to complete it, as it almost certainly will. If you’re still in doubt and want to confirm that the update hasn’t frozen, open Activity Monitor and look for around 100% CPU from softwareupdated or related processes, and disk activity.

Unfortunately, there’s nothing the user can do to accelerate macOS updates.

After Alexandre Calame’s views of Lake Geneva painted in the middle of the nineteenth century, the next great artist to devote as much attention to the lake was Ferdinand Hodler, a native of Bern, Switzerland. At the age of eighteen, Hodler had walked across the country to attend the Collège de Genève there, and train as a painter, initially by copying Calame’s paintings.

Hodler started painting a series of views from the north-eastern shore of Lake Geneva looking south, across to the major peaks of the Chablais Alps. He was to continue this series until his death twenty years later. Lake Geneva from Chexbres from about 1898 shows one of the first of these, painted near the village of Chexbres, between Lausanne and Montreux, in early winter.

Lake Geneva from Saint-Prex (1901) is another view across the lake, from a town to the west of Lausanne, looking south with a closer view of the peaks of the Chablais Alps. This appears to have been painted in the summer, with the trees in full leaf and a rich range of flowers. The clouds over the mountains are starting to become more organised in a regular rhythm, a trend that resulted in some of his most distinctive later landscapes.

The Grammont (1905) shows this mountain in the Chablais Alps, to the south of the eastern end of Lake Geneva, towards which many of Hodler’s favourite views over that lake were aimed. Again he uses a limited palette; the lake itself reminds me of Gustav Klimt’s wonderful paintings of Attersee from a few years earlier, although Hodler’s darker blue ripples quickly vanish as the lake recedes from the viewer.

The following year, he painted Landscape at Lake Geneva.

One of the clearest examples of Hodler’s distinctive Parallelist landscapes is his Rhythmic Landscape on Lake Geneva from 1908. This was a second version of a view he had previously painted in 1905, when he wrote “This is perhaps the landscape in which I applied my compositional principles most felicitously.”

Most of his symmetry and rhythm is obvious; what may not be so apparent are the idiosyncratic reflections seen on the lake’s surface. The gaps in the train of cumulus clouds here become dark blue pillars, which are optically impossible, but are responsible for much of the rhythm in the lower half of the painting.

In the final years of Hodler’s life he painted some of the most sublime landscapes of his career. During the winter of 1917-18, his health deteriorated, but he continued to paint from the window of his room in Geneva, completing more than eighteen views during those final months. Here are three examples.

In Lake Geneva with Mont Blanc by Morning Light (1918), one of the more complex paintings of this series, bands represent the lake shore, four different zones of the surface of the lake, the lowlands of the opposite bank, the mountain chains, and two zones of colour in the dawn sky. The lower section of the sky and the foreground shore echo in colour, and contrast in their pale lemon-orange with the blues of the other bands.

Lake Geneva with Mont Blanc in the Morning Light (1918) has a simpler structure, with the water, a band of reflections, the mass of the far shore and mountains merged, and the dawn sky. The dominant colour is the yellow to pale red of the dawn sky and its reflection.

Lake Geneva with Mont Blanc in the (Red) Dawn Light (1918) is also simpler in its structure, with the water coloured by the sky, a zone of blue reflections of the far bank, the merged distant shore and mountains, and the sky.

In Hodler’s ultimate and most sublime landscapes, he eliminated the unnecessary detail, stating just the elements of water, earth, air, and the fire of the rising sun, in their natural rhythm. On 19 May 1918, Hodler died in Geneva, at the age of 65.

One of the longstanding jokes in computing is how misleading progress indicators can be, and last week most of us had a timely reminder when we updated macOS. However much we might like a perfectly accurate linear indicator for macOS updates, this is one of those situations where the best we can expect is a compromise, as I tried to explain here.

Showing progress

There are two types of progress indicator, determinate and indeterminate, depending on whether the task is quantifiable and progress is measurable. Determinate indicators are always preferred, as they inform the user whether they need only wait only a few moments, or they have time to enjoy a leisurely meal, but that requires quantifiability and measurability.

The simple example is copying a file from one disk to another: although macOS doesn’t know in advance how long that might take, it can quantify the task as the size of the file to be copied, then keep track of how much of that has already been completed. When half the size of the file has been copied, the progress bar can be set to half-way along its total length, so providing an accurate indication of progress.

However, with some copy operations that breaks down: when copying a sparse file between APFS volumes, for example, only the sparse data is copied, not the whole file size. As a result, copying sparse files often results in progress bars that jump from a low point to completion in the twinkling of an eye. This also relies on the quantities involved being linearly proportional to the time required, an assumption that often breaks down when downloading from a remote server.

macOS updates

Updating macOS consists of a series of many tasks (see references at the end), of which only one, downloading, is both quantifiable and has measurable progress, and even that may be far from linear. Apple therefore has a choice of:

• Display multiple progress indicators, appropriate to each phase. While that might work well for the download phase, it can’t work for others, including preparation, which is likely to take a period of several minutes at least.
• Combine those into a single progress bar, as at present.
• Use an indeterminate progress indicator, such as a spinning wheel, which would be reliable but unhelpful.

As downloading is the one task that is quantifiable and its progress is measurable, I’ll start there.

For this, the progress bar starts an an arbitrary 15%, and softwareupdated assumes the total size of that download is the magnitude of that task.

When the download has been completed, the progress bar reaches an arbitrary 55%, and its caption then changes to reporting progress with preparation.

There is a weakness in the assumption that becomes obvious when downloading from a local Content Caching server, as the final 1 GB or so normally isn’t provided from the cache, but has to be freshly downloaded from Apple’s servers. However, that isn’t normally apparent when caching isn’t available and the whole of the download comes from the same remote source.

For the remainder of the progress bar, between 0%-15% and 55%-100%, the task is neither quantifiable nor measurable. Instead, softwareupdated divides it into a series of subtasks, each of which has a fixed progress level. One list of subtasks and levels obtained from the log is given in the Appendix at the end.

The disadvantage of that strategy is that time required by each subtask varies with the update and the Mac being updated. Inevitably, computationally intensive subtasks will proceed more rapidly on newer and faster Macs, while those mainly constrained by disk speed should be more uniform. Large updates should take significantly longer, and that will vary by subtask as well.

The last 5 minutes

A particular problem with some more recent macOS updates, including that from 26.3.1 to 26.4 last week, has been unmarked progress over the final “5 minutes” of preparation. While indeterminate progress indicators continue to move over that period, and reassure the user that the task hasn’t ground to a halt or frozen, the progress bar shown had no intermediate points, making it easy to misinterpret as failure to progress. If this is going to be a feature of future macOS updates, Apple needs to insert some intermediate points to let the user know that the update is still proceeding.

Conclusion

A progress bar that combines different measures of progress, such as download size and substages, can work well, but only if the user is aware of how to read it. As we only update macOS a few times each year, that isn’t sufficient exposure, and how it works needs to be made explicit.

Previously

How macOS 26 Tahoe updates 1
How macOS 26 Tahoe updates: 2 Finite state machines
How macOS 26 Tahoe updates: 3 Catalogues and preparing to download
How macOS 26 Tahoe updates: 4 Download, preparation and installation
Read the macOS update progress bar

Appendix

Progress bar percentages set for some subtasks during updating macOS 26.2 to 26.3 on an Apple silicon Mac:

• 000.1 ACCEPTED
• 000.2 STARTUP
• 000.3 LOADING_PERSISTED
• 000.5 PURGING
• 000.6 CANCEL_SUCORE
• 000.7 CANCEL_MSU
• 000.8 CANCEL_STATE
• 000.9 READY
• 001.0 RELOADING_SU
• 002.0 RELOADING_ROSETTA
• 003.0 RELOADING_UPDATE_BRAIN
• 004.0 DOWNLOADING_UPDATE_BRAIN
• 007.0 PREFLIGHT_WAKEUP
• 009.0 PREFLIGHT_PREREQUISITE
• 010.0 PREFLIGHT_PERSONALIZE
• 015.0 DOWNLOADING_ROSETTA
• 016.0 DOWNLOADING_UPDATE
• 054.0 DOWNLOADED_UPDATE
• 055.0 PREFLIGHT_FDR_RECOVERY
• 060.0 PREPARING_UPDATE
• 099.0 PREPARED
• 100.0 COMPLETED

Note the majority of the progress period (79%) is assigned to downloading (15%-55%) and preparing (60%-99%).

This weekend we’re off to visit Lake Geneva, also known by its French name of Lac Léman, the largest in Switzerland. It’s located in the far south-west of the country, where it forms much of its border with France. It makes a broad arc running north-east from the capital city of Geneva, with some of the highest peaks of the Alps to its south.

Today I start with a selection of paintings almost exclusively from the nineteenth century, when Switzerland was on the itinerary of the Grand Tour undertaken by aspiring young men of the upper class in both Europe and the Americas.

The city of Geneva has long attracted artists, and it was here the eccentric pastellist Jean-Étienne Liotard was born and later kept his studio, and where he eventually retired. His View of the Mont Blanc Massif from the Artist’s Studio from 1765-70 reveals only a little of the southern extreme of the lake, with a cameo self-portrait.

JMW Turner was by no means the first to paint the lake, but his watercolour of Lake Geneva and Mount Blanc from 1802-05 is one of its earliest depictions by a major artist. This view looks south-east over the city of Geneva towards the Mont Blanc massif in the far distance.

Alexandre Calame’s View of Bouveret from 1833 shows a grey heron fishing on the shore at the southern end of the lake, close to the border with France.

While Turner had toured the Alps once travel from England had become possible again in the early nineteenth century, Calame pioneered the painting of views like this of the lake, completed in his studio in 1849. It includes some of the distinctive sailing boats of the Swiss lakes, and a small bird in the shallows, but not a heron here.

In the middle of the nineteenth century, several major American artists visited Switzerland to develop their skills painting mountain views. Despite its finish, John Ferguson Weir’s Lake Leman (Lake Geneva), Switzerland may have been painted in front of the motif, on 11 June 1869.

Following Gustave Courbet’s release from prison for his involvement in the Paris Commune and destruction of the Vendôme Column in 1871, he was forced to flee to the safety of Switzerland, where he lived his remaining years there, unable to return to France.

Courbet painted some of the finest landscapes of his career during his exile in Switzerland, like this Sunset over Lac Léman from 1874, the year of the First Impressionist Exhibition in Paris.

He became particularly obsessed with the island château at the extreme eastern end of Lake Geneva, Chillon Castle, here in 1875. This picturesque château dates back to a Roman outpost, and for much of its recorded history from about 1050 has controlled the road from Burgundy to the Great Saint Bernard Pass, a point of strategic significance. It has since been extensively restored, and is now one of the most visited mediaeval castles in Europe.

Chillon Castle from 1874-77 is another of the views he painted of the castle on the lake.

Sunset on Lake Geneva from about 1876 is reminiscent of Courbet’s earlier seascapes with breaking waves, but now the water is calm once more.

In May 1877, the French government informed Courbet that the cost of rebuilding the Vendôme Column would be over 300,000 Francs, which he could pay in instalments of 10,000 Francs each year, starting on 1 January 1878. Courbet died in Switzerland the day before, on 31 December 1877, at the age of only 58.

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

1: The future was here 25 years ago when the fastest land animal arrived.

2: This atelier came with more than a marathon four years ago.

3: Wicked fast at 40 MHz, its special effects impressed 36 years ago.

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.

Input and output have long been key factors in computer performance, and capable of bringing everything to a crawl unless carefully managed. This is most obvious when foreground and background processes contend for common resources such as disk storage. A popular solution has been to impose delays on I/O performed for intensive background tasks, like backing up, so giving more important tasks preferential access to I/O. This policy is known as I/O throttling, and has come to determine hardware choice.

For example, folk wisdom is that there’s little point in wasting a faster drive to store your Time Machine backups, because when those backups are made, their write speed is throttled by macOS.

I/O Throttling

Documentation of I/O policy is in the man page for the getiopolicy_np() call in the Standard C Library, last revised in 2019, and prevailing settings are in sysctl’s debug.lowpri_throttle_* values. Those draw a distinction between I/O to local disks, being “I/O sent to the media without going through a network”, such as I/O “to internal and external hard drives, optical media in internal and external drives, flash drives, floppy disks, ram disks, and mounted disk images which reside on these media”, and those to “remote volumes” “that require network activity to complete the operation”. The latter are “currently only supported for remote volumes mounted by SMB or AFP.”

Inclusion of remote volumes is a relatively recent change, as in the previous version of this man page from 2006, they were explicitly excluded as “remote volumes mounted through networks (AFP, SMB, NFS, etc) or disk images residing on remote volumes.”

Five policy levels are supported for IOPOL_TYPE_DISK:

• IOPOL_IMPORTANT, the default, where I/O is critical to system responsiveness.
• IOPOL_STANDARD, which may be delayed slightly to allow IOPOL_IMPORTANT to complete quickly, and presumably referred to in sysctl as Tier 1.
• IOPOL_UTILITY, for brief background threads that may be throttled to prevent impact on higher policy levels, in Tier 2.
• IOPOL_THROTTLE, for “long-running I/O intensive background work, such as backups, search indexing, or file synchronization”, that will be throttled to prevent impact on higher policy levels, in Tier 3.
• IOPOL_PASSIVE, for mounting files from disk images, and the like, intended more for server situations so that lower policy levels aren’t slowed by them.

However, the idea that throttled I/O is intentionally slowed at all times isn’t supported by the explanation of how throttling works: “If a throttleable request occurs within a small time window of a request of higher priority, the thread that issued the throttleable I/O is forced to a sleep for a short period. This slows down the thread that issues the throttleable I/O so that higher-priority I/Os can complete with low-latency and receive a greater share of the disk bandwidth.”

Settings in sysctl for Tier 3 give the window duration as 500 milliseconds, and the sleep period as 200 ms, except for SSDs, whose sleep period is considerably shorter at just 25 ms. Those also set a maximum size for I/O at 131,072 bytes. You can view those settings in the debug section of Mints’ sysctl viewer.

Some years ago it was discovered that the user can globally disable IOPOL_THROTTLE and presumably all other IOPOL_TYPE_DISK policy with the command
sudo sysctl debug.lowpri_throttle_enabled=0
although that doesn’t persist across restarts, and isn’t documented in the man page for sysctl. This is provided in an option in St. Clair Software’s App Tamer, to “Accelerate Time Machine backups”, for those who’d rather avoid the command line.

Apple silicon Macs

Since the man page for getiopolicy_np() was last revised, Apple silicon Macs have changed I/O. Most is now handled in some way through specialised Arm cores within the chip, and CPU cores come in two (now three) types, Efficiency and Performance (and Super in the M5 family). Background threads such as those performing the work associated with IOPOL_THROTTLE are now most likely to be running on Efficiency (or M5 Performance) CPU cores.

If you wanted to do away with all throttling, you not only have to change the debug.lowpri_throttle_enabled setting, but you’d need to move those background threads to run them on Performance (M5 Super) CPU cores, which isn’t possible unless you have control over the code. There is evidence that macOS may do this anyway when performing the first full Time Machine backup, which achieves significantly faster speeds than subsequent incremental backups.

Dangers

The big disadvantage of completely disabling I/O throttling policy is this can only be applied globally, so including I/O for Spotlight indexing, file synchronisation, and other background tasks, as well as those needing high-priority access to I/O. Leaving the policy disabled in normal circumstances could readily lead to adverse side-effects, allowing Spotlight indexing threads to swamp important user storage access, for example.

Conclusions

Even when Macs were simpler and all CPU cores were the same, disabling I/O throttling was at best experimental, and ran the risk of compromising higher priority I/O. In Apple silicon Macs, relocating threads from E to P cores isn’t possible, except when running them in a virtual machine. Without that, there seems little if any benefit from disabling I/O throttling. However, the claim that there’s no performance benefit to be obtained from faster backup storage media is demonstrably false. Perhaps it’s time to return I/O throttling to the obscurity it deserves.

The great Symbolist painter Gustave Moreau was born almost two centuries ago, on 6 April 1826. To mark his bicentenary early next month, this short series outlines his career in a small selection of his more important paintings. They are at once history, symbolic explorations, as phantasmagoric as the most radical of William Blake or Odilon Redon, and torrents of figures and forms drawn from all human cultures. They’re elaborate, complex, and appear to defy reading.

Moreau was a precocious artist who started copying in the Louvre, in his native Paris, when he was only seventeen. A year later he started attending a private studio run by François-Édouard Picot, to prepare him for the entrance exam for the École des Beaux-Arts. In Picot’s studio, he learned the methods to which he adhered for the rest of his career: each painting started with a series of drawings, which developed both composition and details. The final drawing was squared up on a grid, to enable its transfer to canvas, where he painted conventionally in oils, using layers.

He was admitted to the École des Beaux-Arts in 1846, and decided to be a history painter. He competed twice for the Prix de Rome, which would have taken him to continue his studies in Rome, but was unsuccessful on both occasions. He therefore left the École in 1849, and started making a precarious living with small commissioned works including favourite scenes from the plays of Shakespeare. His work changed markedly in 1851, the year that JMW Turner died, when he befriended Théodore Chassériau, a former pupil of JAD Ingres; Moreau set up his first studio near Chassériau’s, and started painting more ambitious works to submit to the Salon.

The Judgement of Paris (1852) is one of his early watercolours, showing great promise of things to come. At its heart is a fairly faithful representation of this classical myth, in which Paris (right of centre) is deciding which of Hera, Athena, and Aphrodite is the most fair, and should be awarded the golden apple given by Eris from the Garden of the Hesperides.

Apollo and the Nine Muses (1856) is another significant step towards his mature work. Apollo, a young and surprisingly androgynous figure, sits in the foreground, his distinctive lyre part-hidden under his right foot. To the right of him is a wild rose, with both white flowers and red hips. The muses cluster on a small mound behind that, equipped for and engaged in their respective arts.

That year, his friend and mentor Chassériau died at the age of only 37. Moreau was devastated, and decided to travel to Italy to complete his education as a painter and resolve his future. From October 1857 to June 1858, he copied Renaissance paintings in Rome, then moved on to Florence, Milan, and Venice. He finally returned to Paris in September 1859, having made about a thousand copies in less than two years. He had also met and made friends with several other artists, including Edgar Degas and James Tissot.

Hesiod and the Muses (1860) is probably the first of Moreau’s novel history paintings, and the first of a series of works showing Hesiod, generally considered to be the first written poet in the Western tradition to exist as a real person, and to play an active role in his poetry. Hesiod is the young man holding a laurel staff in his right hand, to the left of centre.

There are four swans on the ground, and one in flight above Hesiod, a winged Cupid sat on the left wing of Pegasus, and a brilliant white star directly above the winged horse. However, the Cupid and Pegasus were only added in about 1883, when the canvas was extended.

Moreau met his mistress and muse Alexandrine Dureux (whom he never married, both remaining single) that year, and set her up in a nearby flat, where she lived until her death in 1890.

By 1864, he had abandoned three attempts to produce a radical work for the Salon. However, he had been working on something different, that he completed during the winter of 1863-4: Oedipus and the Sphinx (1864)

This was a bold move. Not only was this painting startlingly original and different, but it visited a motif that had recently resulted in Ingres’ success at the Salon, in 1827. Just as Oedipus is seen to be staring out the fearsome sphinx, so Moreau was visibly challenging his seniors.

This shows a key scene from Sophocles’ tragedy Oedipus the King. The sphinx had effectively put the ancient Greek city of Thebes under siege, by sitting outside and refusing to let anyone pass unless they answered a riddle correctly. Those who failed to do that it killed by strangulation. When Oedipus arrived, intending to enter Thebes, the sphinx asked him “Which creature has one voice and yet becomes four-footed, two-footed, and three-footed?” Oedipus solved this in his answer of humans, who crawl when a baby, walk on two feet as an adult, then walk with a stick when old. The defeated sphinx then threw itself into the sea below, Oedipus entered Thebes, was awarded the throne of Thebes in return for destroying the sphinx, and married its queen Jocasta, who turned out to be his mother.

The apparently emotionless faces of Oedipus and the sphinx are not an attempt to reject facial expression as a narrative tool. In fact, they confirm its value. The pair are engaged in staring intently into one another’s eyes, in the way that poker players might, almost eyeball to eyeball. The most plausible moment to be shown here is the brief interval between the sphinx asking its riddle, and Oedipus answering it.

The sphinx has already latched onto the front of what it comfortably assumes is going to be another, rather delectable victim. Its forelegs are ready to reach up and strangle him once he guesses the wrong answer, and its hindlegs are ready to unsheath claws and walk up, burying them in his flesh. The sphinx is ready to prove itself a femme fatale for Oedipus.

Oedipus knows that he cannot falter. A false guess, even a slight quaver in his voice, and this beautiful but lethal beast will be at his throat. His left hand clenches his javelin, knowing that what he is about to say should save his life, and spare the Thebans. He will then no longer be pinned with his back to the rock, and the threat of the sphinx will be gone.

Around this central narrative core, Moreau feeds us symbolic morsels to supplement that main course without supplanting it. Behind Oedipus is a bay tree, sacred to Apollo, representing man’s highest achievements; behind the sphinx is a fig tree, a traditional symbol of sin. The small polychrome column at the right is topped by a cinerary urn, symbolising death, and above it is a butterfly, representing the soul. Ascending the column is a snake, again associated with death, and through the biblical serpent, with sin.

Moreau’s bold move worked, as Oedipus and the Sphinx took the Salon of 1864 by storm, winning him a medal. The following year, he tried to consolidate that success with Jason.

The name Jason refers, of course, to Jason of Golden Fleece and Argonauts fame, a series of swashbuckling adventures offering ample opportunities for theatrical narrative painting. Moreau avoids them all, and shows us a static Jason, with Medea stood behind him, not a Golden Fleece in sight. Instead of providing narrative, the artist offers us symbols as clues to what might be going on.

The broad outline of Jason’s story is simple. When he reached Colchis, he underwent a series of trials imposed by King Aeëtes, culminating in his victory over the dragon guarding the Golden Fleece. These were accomplished with the help of Medea, the King’s daughter, in return for a promise of marriage.

The almost naked woman behind Jason is Medea, the sorceress who has fallen in love with the hero. The ram’s head at the top of the pillar on the left signifies the Golden Fleece, and the dragon which guarded it is shown as the eagle on which Jason is standing, with the broken tip of his javelin embedded in it. This is the more confusing, as in the original story the dragon was put to sleep by one of Medea’s potions, rather than being killed with a javelin.

Yet Medea holds a vial in her right hand, and her body is swathed with the poisonous hellebore plant, a standard tool of witchcraft. These may allude to Jason’s future rejection of Medea and her poisoning of his replacement bride, but there is a lot of story between this moment and that later episode, so that is speculative and hardly clarified by the painting.

Moreau provided some clues to his intentions in this painting, in the almost illegible inscriptions on the two phylacteries wound around the column. These bear the Latin:
nempe tenens quod amo gremioque in Iasonis haerens
per freta longa ferar; nihil illum amplexa timebo
(Nay, holding that which I love, and resting in Jason’s arms, I shall travel over the long reaches of the sea; in his safe embrace I will fear nothing)
et auro heros Aesonius potitur spolioque superbus
muneris auctorem secum spolia altera portans
(And the heroic son of Aeson [i.e. Jason] gained the Golden Fleece. Proud of this spoil and bearing with him the giver of his prize, another spoil)
(Cooke, pp 55-56.)

These could be interpreted as suggesting that the painting should be read in terms of the conflict between Jason and Medea: Medea expresses her subjugate trust in him, while Jason considers her to be just another spoil won alongside the Golden Fleece. More puzzling is the spattering of other details, of hummingbirds, the sphinx on top of the pillar, medals decorating the shaft of that pillar, and more. Some appear merely to be decorative, but drawing the line between the decorative and the symbolic is impossible.

The end result in Jason is almost the opposite of Oedipus and the Sphinx: the latter consists of a clear narrative lightly embellished with symbols, the former relies on the interpretation of symbols to construct any narrative; as those symbols conflict with the original narrative, the viewer can readily become bewildered.

The 1865 Salon didn’t provide the consolidation for which Moreau had hoped, although much of that was the result of an accident of history: dominating all discussion that year was another painting, Manet’s Olympia. He needed to do better in 1866 if he wasn’t going to slip back into obscurity.

In Moreau’s Orpheus (1865) a sombrely-dressed Thracian woman holds Orpheus’ lyre, on which rests his head, blanched in death, as if affixed to the lyre like the head of a hunting trophy. Her eyes are closed in reverie.

One version of the legend of Orpheus’ death holds that his head and lyre were borne by the river Hebrus, which is shown in the background landscape to the right. Again, though, Moreau pursues his own adjusted version of the written narrative, as according to that account (in Ovid’s Metamorphoses, book 11), the head and lyre were washed up on the coast of Lesbos.

Orpheus adopts a unified tonality, colour, form, character, and style that could be viewed as a ‘mode’, as conceived by Nicolas Poussin. The gentle and natural beauty of the Thracian woman, her ornate clothes, flowers, and the strange beauty of Orpheus’ head on the lyre contrast with a harsh and barren landscape, which might have been more appropriate in a Renaissance painting, perhaps by Leonardo da Vinci.

Moreau has carefully avoided elaborate symbols and decoration, although he has left us two further puzzles at the painting’s corners: the three figures, apparently shepherds, on the rocks at the upper left, and a pair of tortoises at the lower right. The figures refer to music, which seems in keeping with Orpheus and his lyre, but the significance of the tortoises is open to speculation.

What Moreau lost in the absence of narrative, this painting gained in its remarkable tranquillity. Two faces, eyes closed, (don’t) look at one another. The intricate decoration of the lyre seems unified with the Thracian woman’s clothing, even the coiled braids of her hair. Although one of his most profoundly beautiful and moving paintings, this failed to impress the Salon.

In 1868-9 he turned to one of the most frequently painted stories from Greek mythology, that of the abduction and rape of Europa. She was the mother of King Minos of Crete, and the story of Cretan origin; the bull was the main sacred animal in Crete. Zeus (Jupiter to the Romans), a notorious ravisher of women, lusted after the beautiful Europa. He therefore metamorphosed himself into a white bull, and hid among Europa’s father’s herd in Phoenicia. When Europa and other maidens came to gather flowers near this herd, she saw the white bull, caressed it, and climbed onto its back.

Zeus then ran to the sea and swam with Europa on his back until they reached the shores of Crete. There he revealed himself, and Europa became the first queen of the island. He gave her in return a necklace, Talos (a giant bronze automaton who protected Crete by circling its shores), Laelaps (an unfailing hunting dog), and a javelin that always struck its target.

Almost universally, previous depictions of this myth have shown the start of the abduction, from the pastures of Phoenicia to the bull heading off to sea. Moreau’s white bull, with Europa riding a precarious side-saddle, has just emerged from the sea, so is presumably now on the island of Crete.

The finished work, known as Jupiter and Europa (1868-9) (I apologise for the lack of sharpness in this image) but titled Europa, shows the bull with a human head, presumably as Zeus has revealed himself to Europa. The head of Zeus recalls those of sculptures of Assyrian kings.

It’s hard to see what Moreau brought in terms of originality to this well-worn motif, and the critics drew comparison with Veronese rather than Titian. Either way, this seems to be a painting in search of a reason, and the Salon agreed. As there was now a small but dedicated group of collectors who were prepared to purchase his paintings, Moreau decided to withdraw from exhibiting at the annual Salon.

In the Franco-Prussian War, Moreau joined the National Guard, and served in the defence of Paris in the autumn of 1870, besieged there with his mother. Over the winter his left shoulder and arm became immobile because of ‘rheumatism’, but he remained in the city. Finally, during the Commune in the spring of 1871, he defended the paintings he had amassed in his home, and watched his late friend Chassériau’s murals in the Cour des Comptes being destroyed by fire. He spent that summer recovering in the spa at Néris-les-Bains in the Auvergne.

References

Cooke P (2014) Gustave Moreau, History Painting, Spirituality and Symbolism, Yale UP. ISBN 978 0 300 20433 9.
Mathieu P-L (1998, 2010) Gustave Moreau, the Assembler of Dreams, PocheCouleur. ISBN 978 2 867 70194 8.

In most respects, lightweight virtualisation of macOS on Apple silicon delivers almost the same performance as running code on the host. That’s the result of having direct access to CPU cores and the GPU. However, earlier implementations in Monterey and Ventura performed poorly when accessing the Data volume in the Virtual Machine, with read/write speeds measured at 4.4/0.7 and 5.4/0.7 GB/s respectively, without FileVault or other encryption. In macOS 26.3.1 both RAW and ASIF encrypted disk images show disappointing performance particularly when writing to them. This article therefore re-evaluates VM disk performance to see if that extends to VMs.

Methods

Tests were performed on two freshly made 100 GB VMs in RAW format using the macOS 26.4 IPSW, running on a Mac mini M4 Pro in macOS 26.4. VMs were given 5 CPU cores and 16 GB memory, didn’t connect to an Apple Account, and were built and run in Viable and Vimy, both of which use the standard macOS API for virtualisation.

Performance was measured using Stibium’s ‘Gold Standard’ with 5 rather than 10 test sets, reading and writing a total of 26 GB in 80 files ranging in size between 2 MB and 2 GB. Following an initial write test, the VM was restarted before performing the read test. The first VM was configured with FileVault enabled, and the second with it disabled. In addition to those, standard read/write performance was measured as before on a 100 GB RAW disk image on the host, and on a 100 GB ASIF image, both being encrypted using 256-bit AES.

Results

Measured read/write speeds were:

• Native SSD, FileVault on – 6.57/7.66 GB/s
• VM, FileVault off – 6.62/5.91 GB/s
• VM, FileVault on – 4.66/3.11 GB/s
• RAW disk image, 256-bit AES – 2.82/1.59 GB/s
• ASIF disk image, 256-bit AES – 2.85/1.76 GB/s.

With FileVault disabled, performance in the VM was surprisingly close to that of the host’s internal SSD, with a small reduction in write speed from 7.66 to 5.91 GB/s. That’s a huge improvement on previous results, with writes being almost ten times faster.

Enabling FileVault did reduce performance significantly, particularly write speed which fell to about half. However, those are still good enough to be acceptable for most purposes.

No significant change was seen in host disk image performance from those measured in 26.3.1, though, which remains substantially slower than the VM with FileVault enabled.

Conclusions

VMs are vulnerable if they don’t have FileVault enabled. Without encryption, sensitive contents would be relatively easy to access if the VM were to fall into the hands of an attacker. Enabling FileVault is thus potentially more important for a VM.

Thankfully, with such great improvements in VM disk performance, those hosted on an Apple silicon Mac’s internal SSD are unlikely to be slowed much by their disk performance.

This makes it the more puzzling that encrypted RAW and ASIF disk images should perform so poorly, and it’s disappointing to see that continues in macOS 26.4. Over the same period that VM disk performance has increased so impressively, that of disk images has headed in the opposite direction.

VMs and BSIs

If you tried installing the recent Background Security Improvement (BSI) in a macOS 26.3.1 VM, you were probably disappointed. In this respect, the VM didn’t work as expected. I was unable to find the BSI in its section in Privacy & Security settings. What did help was downloading it using SilentKnight, although that can’t install BSIs successfully. Instead, I restarted the VM and Privacy & Security offered to install the BSI at last.

Once installed, Privacy & Security offered to remove the BSI, but failed to do so, with SecurityImprovementsExtension reporting:
Rollback failed: Error Domain=SUOSUErrorDomain Code=103 "Unable to remove Background Security Improvement" UserInfo={NSLocalizedDescription=Unable to remove Background Security Improvement, NSLocalizedRecoverySuggestion=Use Software Update to install the latest version of macOS.}

For the time being BSIs appear dysfunctional in VMs.

Although Naturalist painting had originated in the countryside among the rural poor, it soon came to record changing times in science. One of the more prominent painters of science and scientists was Léon Lhermitte, now known almost entirely for his rural paintings.

Claude Bernard (1813-1878) was a pioneering physiologist whose writings were of great influence to Naturalists, including Émile Zola. Following Bernard’s death, the Sorbonne (where he had taught) commissioned Lhermitte to paint his portrait in 1886. This is a faithful anonymous copy of Claude Bernard and His Pupils, which was exhibited at the Salon in 1889. This shows Bernard in the midst of performing an experiment on a rabbit, his students discussing its results, and one writing the experimental observations in the laboratory daybook.

Lhermitte’s painting of The Chemist Henri-Étienne Sainte-Claire Deville, Lesson on Aluminium from the following year was also commissioned by the Sorbonne in Paris; I apologise for the small size of this image. Henri-Étienne Sainte-Claire Deville (1818-1881) was responsible for many significant discoveries in chemistry, the most important being a method for the industrial manufacture of aluminium. He’s shown here surrounded by objects made from this new material, which quickly came to transform manufacturing and to invade every home.

Several Naturalist painters were commissioned to paint murals depicting scientific events for universities. Among them is Erik Henningsen’s The Nordic Natural Science Research Meeting 14 July 1847, completed in 1895 for the Aula of the University of Copenhagen. Presiding over this scientific meeting was the great Danish physicist and chemist Hans Christian Ørsted, who was nearly seventy at the time.

Technology was also becoming commonplace at work.

Charles Frederic Ulrich painted a young apprentice drinking during a moment’s pause in his work in The Village Printing Shop, Haarlem (1884). In the background is a large and relatively modern printing press.

Another Naturalist artist, Jean-Eugène Buland, in his Un Patron, or The Apprentice’s Lesson from 1888 shows a young boy being trained to make a cogwheel. This was part of the French industrial recovery following its defeat in the Franco-Prussian War.

The subject of Louis Muraton’s The Photographer, painted before 1901, is rocking a glass plate in a bath of developer, in his improvised darkroom, another sign of the times.

Major innovations in medical procedures and care were introduced, and duly recorded in Naturalist paintings.

In André Brouillet’s A Clinical Lesson at the Salpêtrière Hospital (1887), an eminent neurologist Jean-Martin Charcot is demonstrating how he could hypnotise Marie “Blanche” Wittman, the ‘Queen of Hysterics’, into suffering hysterical collapse. Charcot and Wittman were a renowned partnership in this ‘act’, who performed in front of Sigmund Freud when he visited the hospital.

In the USA, Thomas Eakins painted the retiring professor of surgery, Dr. David Hayes Agnew, at work in the University of Pennsylvania School of Medicine. The patient is unconscious thanks to a volatile liquid general anaesthetic administered via a mask. Bright surgical lighting puts six figures literally in the limelight, including that of Agnew, holding a scalpel at the left.

Robert C. Hinckley’s Ether Day, or The First Operation with Ether, painted between 1882-93, recreates the scene on 16 October 1846 in what is now known as the Ether Dome in the Massachusetts General Hospital, Boston, MA. Here John Collins Warren is removing a tumour from the neck of a local printer, Edward G Abbott, who was anaesthetised using ether, in its first recorded use for a general surgical procedure; I apologise for the poor quality of this image.

Finally, Anna Sahlstén’s Surgery in Hospital from about 1893 shows the dazzling whiteness of the modern hospital, with a smart professional nurse caring for a child patient in the background. On the wall is a large radiator for the hospital’s modern heating system, which replaced the old stoves seen in so many earlier images of hospital wards.

Updating macOS is a far more complex series of processes than it used to be, and the progress bar displayed in Software Update settings is complicated as a result. To capture all the phases that precede installation of an update, the progress bar moves through a series of stages, only one of which is downloading. This article identifies and explains them.

Start

When the Software Update pane offers a macOS update, it has already done a lot of the preliminary work, in fetching the catalogue of updates, checking through them to determine which could be installed, and working out what that would require. This enables it to provide a first estimate of how much needs to be downloaded. Note this is only an estimate at this stage, and may not include additional components such as an update to Rosetta 2.

Once you’ve agreed to install the update now, the progress bar is displayed.

Progress shown here covers many different processes, of which the most substantial are the download and preparation phases. Although progress shown during the download will vary depending on the speed of your Mac’s connection with Pallas, Apple’s software update servers, other sections are determined by the completion of tasks required for the installation, and may proceed in fits and starts.

Before the download can begin, softwareupdated has initial preparations to make, including reloading and downloading the Update Brain responsible for much of the task of installation. Following that are extensive preflight checks, and together those account for the first 15% of the progress bar shown. On a fast Apple silicon Mac, the progress bar may jump straight to that 15%.

Download

This starts at that arbitrary 15%, and is completed when the bar reaches 55%. In between those it should progress according to download speed, but that can be highly non-linear.

This displays a more accurate total size for the download, and the current amount that has already been downloaded. In this case, the bulk of this update is coming over the network from my Content Caching server, so its initial estimate is for a brief period of just 2 minutes. The progress bar then moves in proportion to the amount downloaded, not the time.

Although most of the download can be cached, for Apple silicon Macs the last 1 GB or so has to be obtained for each update from Pallas. As a result, the progress bar suddenly slows as it’s approaching 55%, and the estimated time remaining increases before decreasing again.

Preparing

As soon as the download is complete, there’s another preflight phase lasting from 55%-60%, then the downloads are prepared for installation. This phase doesn’t apparently involve their decompression, which is largely performed on the download stream during the download phase.

Preparations are arbitrarily assigned a period of 30 minutes to complete, but now seldom if ever require that long. As they’re allocated to the last 40% of the progress bar, this phase usually completes much quicker than the times given.

The final 5 minutes are often the slowest, and can take a few minutes longer than that, as the files for installation are gathered into a ‘stash’ ready for the Update Brain to install. Because the progress bar tends to jump straight from 95% complete to 100% this can make it look as if the update has frozen.

Installing

As soon as preparations are complete and reach 100% on the progress bar, the Mac prepares to restart into the installation phase, for which you’re given a 1 minute countdown before the screen goes black and installation happens.

Progress bar key phases

• 0-15% preparation, preflight; usually brief
• 15-55% download; on Apple silicon Macs, last 1 GB usually can’t be cached, so slower
• 55-60% preflight; brief
• 60-100% preparing; last 5 minutes may be longest.

I hope this helps you make sense of what you see during macOS updates, at least until the screen goes black and the installation starts.

Apple has just released its regular weekly update to XProtect, bringing it to version 5335. As usual it doesn’t release information about what security issues this update might address.

This version adds two new Yara rules for MACOS.TIMELYTURTLE.OBDR and MACOS.SOMA.MAENB, and amends the existing rule for MACOS.SOMA.BYTE.SEQUENCE.B. In the Osascript rules in XPScripts.yr, it relocates those for TABUPA, REBUPA, DUVAST, DUCUHA and DUSTCO.

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_15-5335

Sequoia and Tahoe systems only

This update has already been released for Sequoia and Tahoe 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 5335 but your Mac still reports an older version is installed, you should be able to force the update using
sudo xprotect update

The original intent of the French Impressionists was to paint quickly in front of the motif so as to capture its impression. Although many Impressionist depictions of reflections aren’t optically faithful, in practice there’s nothing to prevent them from that. This was amply demonstrated by the grandfather of Impressionism, Camille Corot, during his formative years spent developing his skills in Rome.

Corot’s earliest plein air works are truly prodigious in their quality, and his development of the art. By the time that the Impressionists were painting outdoors, after 1841, oil paint was widely available in far more convenient metal tubes. But when Corot was in Italy he enjoyed no such luxuries: paint came in small bladders that were far less portable and messier to work with. Despite that, his view of The Island and Bridge of San Bartolomeo from 1825/8 appears optically accurate.

Corot’s View of Rome: The Bridge and Castel Sant’Angelo with the Cupola of St. Peter’s from 1826-7 is another brilliant example painted on paper in front of the motif.

Claude Monet’s reflections are generally shown on broken water, and appear intended to be optically correct.

Monet painted The Thames below Westminster while he was in London in 1871, and returned over thirty years later to paint more radical series of views in different lighting conditions.

The following year, he painted this view of his home port of Le Havre, which gave rise to the movement’s name, Impression, Sunrise. This appears to be a brisk oil sketch of fog and the rising sun, and is one of his series depicting the port at different times and in varying lights, exhibited in the First Impressionist Exhibition two years later.

The same year, Alfred Sisley’s view of The Canal Saint-Martin, Paris shows a placid and almost disused stretch of canal near the centre of Paris. This too appears to be optically correct.

In 1873, Monet painted his masterwork Autumn on the Seine, Argenteuil, a textbook example of a river landscape in autumn painted in high Impressionist style, with high chroma, loose brushstrokes and faithful reflections.

Although Monet’s View of the Church at Vernon from 1883 doesn’t appear entirely optically accurate, its intent is clear. The reflection of the large house at the right is extended a little too far to the right, as if there had been a tall tree beside it on the bank, where the original image shows another lower house set further back.

Some of Monet’s later series relied on reflections for their visual effects, although they also take more optical liberties.

In 1891, Monet painted his first formal series showing poplars, including Poplars on the Bank of the Epte, Autumn. These articulate the contrasts in form within each tree, with sections of bare trunk, and those of extensive canopy, the colours cast by light and those of the leaves themselves, the rhythmic assembly of the line of trees, their reflections on the water, and the formation of the line of poplars into sweeping curves in depth.

The broken water surface in Sisley’s Bend on the Loing at Moret from 1886 remains surprisingly faithful.

In Moret Bridge in the Sunlight from 1892, Sisley captures the reflections of the buildings dominating the centre of this small town on the River Loing.

Claude Monet’s return to London in 1903 revisits The Houses of Parliament, Sunset fairly faithfully.

Like any file, a disk image can become corrupt or damaged, and like any mountable disk its file systems can also become corrupt or damaged. Although those should be very infrequent, their results can disastrous, and render the contents of that disk image inaccessible. This article suggests some solutions you can try.

In theory, if the problem is in the image’s file systems, you should be able to mount its volumes and run First Aid in Disk Utility to check and repair them. In practice that seldom works out, as macOS usually refuses to mount the image. Unless you have ready access to a recent backup, all you can do then is resort to Terminal’s command line to attempt a recovery.

Gaining access to the contents of a disk image requires two steps to complete: first the image must be attached as a device, then after probing of the file systems it contains, those can be mounted.

Read-only and compressed disk images have a checksum stored, and this is normally verified against the image file data first. If that proves invalid, then macOS will refuse to go any further.

In the past, records of checksum verifications have been stored in extended attributes such as com.apple.diskimages.recentcksum, and sometimes deleting those, or a record of the file systems being checked using fsck in com.apple.diskimages.fsck, can allow the disk image to mount. More recently those appear to have fallen into disuse.

Next you should try to attach the disk image without verification or mounting. This is best done using a command such as
hdiutil attach -nomount -noverify diskImagePath
where diskImagePath is the full path to the disk image file, such as /Users/hoakley/VMs/myImage.dmg

If this succeeds, you’ll be rewarded with a list of the resulting devices, such as
/dev/disk4 GUID_partition_scheme
/dev/disk4s1 EFI
/dev/disk4s2 Apple_APFS
/dev/disk5 EF57347C-0000-11AA-AA11-0030654
/dev/disk5s1 41504653-0000-11AA-AA11-0030654

The first is the disk device disk4, and is followed by its two standard partitions disk4s1 and disk4s2. The latter is its APFS container disk5 with its single APFS volume disk5s1. You can now check and repair the last two of those, such as
fsck_apfs -y /dev/disk5s1
which should return a blow-by-blow account of the results. If the file system is HFS+ you may also be able to use third-party repair tools such as DiskWarrior.

When you’ve completed the required repairs, detach the disk image with a command like
hdiutil detach /dev/disk4

If that fails to make the disk image mountable, some have claimed success by converting the disk image to a different format, using a command like
hdiutil convert diskImagePath -format Uxxx -o outImagePath
where diskImagePath is the original disk image, outImagePath is the new image to be created, and Uxxx is the name of a disk image type, as listed in the Appendix.

If none of these gives access to the contents you require, then it’s almost certain that the only way ahead is to find the latest backup of that disk image, and use a copy of that.

Appendix: Supported disk image formats

• UDRW – UDIF read/write, sparse file from macOS 12
• UDRO – UDIF read-only
• UDCO – UDIF ADC-compressed
• UDZO – UDIF zlib-compressed
• ULFO – UDIF lzfse-compressed (OS X 10.11)
• ULMO – UDIF lzma-compressed (macOS 10.15)
• UDTO – DVD/CD-R master for export
• UDSP – sparse image, grows with content
• UDSB – sparse bundle, grows with content, bundle-backed, Mac OS X 10.5
• UFBI – UDIF entire image with MD5 checksum.
• ASIF – sparse image, grows with content, macOS 15.

The update to bring macOS Tahoe up to version 26.4 is hefty at around 7.15 GB (more than double that if you’re unlucky), and reflects a great deal of bug fixes and improvements in almost every subsystem. Apple provides three good sets of release notes:

• General release notes include the addition of an option to use compact tabs in Safari, Freeform’s new Creator Studio enhancements, and a facility for Purchase Sharing in Family Sharing. Oh, and the requisite eight new emoji.
• Enterprise release notes are extensive, but contain little for the non-enterprise user.
• Security release notes list over 70 fixes, many of which are significant, but none are reported as being known to be exploited in the wild at present.

The new build number of 26.4 is 25E246. The Darwin Kernel version is 25.4.0, and XNU 12377.101.15~1.

Apple silicon firmware is updated to a completely different version numbering system, and is now reported as mBoot version 18000.101.7. If you’re running SilentKnight older than version 2.14 (71), then it’s likely that it will crash as a result of this change in firmware version. Please use version 2.14 from here.

Firmware in Intel Macs with T2 chips remains with the previous system, and is updated from 2094.80.5.0.0 (iBridge 23.16.13120.0.0,0) to 2103.100.6.0.0 (iBridge 23.16.14242.0.0,0).

Looking through the bundled apps and /System/Library, there are a great many increments in build numbers reflecting the extensive changes made. Here are a few of the more substantial changes found.

In bundled apps:

• Books goes from version 8.1 to 8.4
• Freeform, version 4.3 to 4.4
• iPhone Mirroring, version 1.5 to 1.6
• Music, version 1.6.3 to 1.6.4
• Safari, version 26.3.1 (21623.2.7.111.2) in BSI (a) to 26.4 (21624.1.16.11.4)
• TV, version 1.6.3 to 1.6.4
• Audio MIDI Setup, version 3.7 to 3.8
• Digital Color Meter, version 6.10 to 6.11
• Screen Sharing, version 6.2 (758.1) to 6.1 (760.4), note the reduction in version number.

In /System/Library:

• AGX kernel extensions all have build increments
• AppleDiskImages2 kext has a build increment
• AppleEmbeddedAudio kext and its plugin kexts have build increments
• AppleIntel Graphics kexts have version increments
• AppleStorageDrivers kext and its plugin kexts have build increments
• APFS is updated from 2632.80.1 to 2811.101.1, suggesting a substantial change has been made
• new private frameworks include ASMExclaveSupport, AccelerateOpt, AlwaysOnExclavesDaemon, AnteroAgent, AppRemoteAssets, AudioPasscodeDSP, BNNSOdieDelegate, CookingData, CoreTransparency, DynamicPrefetching, InAppFeedback, NanoPassKit, PartnerVisualSearch, a whole family of Unilog frameworks, and a group of iCloudWeb frameworks
• mdimporters updated include those for Application, CoreMedia, Mail, Office, iWork but not RichText.

After seeing the new CookingData private framework, I looked out for RecipeKit, but was disappointed not to see it.

This is probably going to be the last such substantial update to macOS Tahoe, as much of Apple’s engineering effort is transferring to make macOS 27 ready for release as a beta at WWDC in early June.

Apple has released the update to bring macOS Tahoe to version 26.4, and security updates for Sequoia and Sonoma to bring them to 15.7.5 and 14.8.5.

Download size for the 26.4 update on Apple silicon Mac is very large, at around 7.15 GB, but only about 4.14 GB on Intel Macs.

Release notes for 26.4 include:

• support for new AirPods Max 2
• compact tabs as an option in Safari
• Freeform joins Creator Studio, with advanced tools and a premium content library
• Purchase Sharing in Family Sharing

and eight new emoji.

Security release notes for 26.4 list over 70 fixes, those for Sequoia 15.7.5 list about 56, and those for Sonoma 14.8.5 list about 50. None are reported as being known to be exploited in the wild at present.

Enterprise release notes for 26.4 are here.

Firmware in Apple silicon Macs is updated to a new mBoot firmware version numbering system, with the current version given as 18000.101.7. The macOS build number is 25E246, and Safari is version 26.4 (21624.1.16.11.4). Firmware in Intel Macs with T2 chips is updated from 2094.80.5.0.0 (iBridge 23.16.13120.0.0,0) to 2103.100.6.0.0 (iBridge 23.16.14242.0.0,0).

If you’re running SilentKnight older than version 2.14 (71), then it’s likely that it will crash as a result of the change in firmware version. Please use version 2.14 from here.

I’ll be posting an analysis of what has changed later today.

Updated 09:15 25 March 2026 with firmware details for Intel Macs.

Of all the painting media, oils give the artist greatest flexibility to change their mind. Even when relatively ‘dry’, they can be scraped back carefully and overpainted, although in many cases overpainting is all that’s required. When such changes are detected by the viewer, they’re often referred to as a pentimento, appropriately the Italian for repentance, with pentimenti in the plural.

Written accounts of artists’ practices and careful examination of their paintings can reveal much about their methods. Some undertake such extensive preparations that painting the finished work invariably goes according to plan. Others may rework their composition extensively as it develops, and leave copious evidence of how they changed their mind.

Several of Leonardo da Vinci’s paintings show how he changed his mind as he worked on the finished painting. His Madonna with a Flower, popularly known as the Benois Madonna, is thought to date from 1481-83, and was preceded in the years 1475-80 by numerous sketches and studies of the Madonna, including several that are strongly linked with this composition. Nevertheless, examination of this painting reveals many pentimenti: the infant’s head was originally larger, and the grasses held by the Madonna in her left hand were originally flowers. Those aren’t visible in this image, though.

Pentimenti can be revealed using special techniques, including infra-red reflectography.

There’s no readily visible evidence that Lucas Cranach the Elder made changes during his painting of The Martyrdom of Saint Catherine in 1504-5.

Cranach had a reputation for being quite an impulsive and rapid painter, which seems to be borne out by more thorough analysis. His early works, in particular, show evidence of repeated adjustments in form and colour. The infra-red reflectogram of the Martyrdom of Saint Catherine, below, shows how he laid down the figures in detail in the underdrawing, but extemporised the pyrotechnic effects.

Considerable changes were made to the details during the painting process, as seen here in the underdrawing of the executioner, and the figures to the right of his head.

Sometimes the ageing of a painting brings pentimenti to light, although they wouldn’t have been visible at the time they were completed.

Christoffer Wilhelm Eckersberg’s Ulysses’ Revenge on Penelope’s Suitors from 1814 shows Odysseus and Telemachus at the left as they attack a small group of the suitors. There are abundant pentimenti visible now in the background, suggesting the artist changed his composition quite radically.

In more modern paintings it can be difficult to distinguish pentimenti from what the artist intended. There are many examples of this in the oil paintings of Paul Cézanne.

Landscape on the Banks of the Oise is an Impressionist view from Cézanne’s first campaign along the River Oise, when he painted in company with Pissarro, and shows the northern bank near the hamlet of Valhermeil.

Closer examination of the reflected image of the house with the red roof merits further study of the painting. Cézanne appears to have made pentimenti to its left edge, at least, and possibly at its right edge too. It appears that an earlier attempt to paint the red roof may have shown it extending more to the left, where it would have been displaced less than now appears.

These can be seen more clearly in the composite image above, in which I have moved the reflected image to the left so that it does align ‘correctly’ with the real image.

In this painting of The Pond of the Jas de Bouffan in Winter, a view Cézanne must have seen almost every day that he went out from his family home, there is evidence of pentimenti in the right side of the reflected image.

Other media are less forgiving. Watercolours can sometimes cope with small changes, but all too often fail completely. Scraping back isn’t normally possible with acrylics, which tend to be overpainted without scraping, as the latter strips the entire paint layer and may also damage the ground.

If you’ve installed Apple’s new Creator Studio versions of what used to be its iWork apps, I’m sure you noticed something odd in your Applications folder. For there, side by side, are apps with exactly the same names, two Keynote.apps, two Numbers.apps, and two Pages.apps. This article explains the trickery that went into that.

We take it for granted that what we see in the Finder is truthful, despite obvious trickery like hidden folders, and iCloud Drive which doesn’t really exist at all. When it comes to bundles like applications, the Finder doesn’t actually show the true folder name, but the bundle name set in that bundle’s Info.plist.

You can get an inkling of what’s going on by selecting the two Pages apps and opening Get Info on each.

The old Pages.app looks straight, giving its Name & Extension as Pages.app as you’d expect.

But the Name & Extension given for the new Pages.app turns out to be Pages Creator Studio.app, and that’s the real name of its app folder.

Check both using my free utility Precize and you’ll see they are completely different, with their own inode numbers and paths. Drag them into Terminal and that shows their true names in the file system, of Pages.app (old) and Pages Creator Studio.app (new).

If you have a property list or text editor handy, copy the Info.plist from inside each app bundle and inspect them side by side.

The old Pages app is still playing this straight:
CFBundleDisplayName = Pages
CFBundleName = Pages
CFBundleIdentifier = com.apple.iWork.Pages

By comparison, the new app is up to no good:
CFBundleAlternateNames = Pages
CFBundleDisplayName = Pages Creator Studio
CFBundleName = Pages
CFBundleIdentifier = com.apple.Pages

Apple provides further details of the contents of Info.plist in this developer article.

There’s a great deal more to accomplishing this with finesse as Apple has done here. Other locations in the app such as its About window and menus also need tweaking to ensure that nowhere breathes a word about the trick that has been pulled. And just to add a bit of spice, apps still using AppKit are quite different from those now using SwiftUI.

My only remaining question is why Apple would want to give the two apps identical names. The primary purpose of setting the CFBundleDisplayName is to accommodate better to the limited display area on devices. An app that has a long full name, like The Time Machine Mechanic, obviously needs to be shortened, and ellipses are a clumsy solution. By giving the app developer the opportunity to display something shorter it makes our iPhones look much neater.

Although it’s a clever trick to pull in macOS, I suspect it’s going to confuse more than it amazes.

Many thanks to Joe who asked this question.

The crusaders led by Godfrey of Bouillon desperately need Rinaldo back if they are to resume their assault on Jerusalem. Guelph’s party, notably the knights Charles (Carlo) and Ubaldo, have gone in search of him. But Rinaldo has been lured into a trap by the sorceress Armida, who intended to kill him. At the last moment, though, she falls in love with him and abducts him in her chariot.

That flies the couple to the distant, deserted and enchanted Fortunate Isles, where she lives in her garden that is perpetually in Spring. The wizard explains this to Charles and Ubaldo, to aid them in their mission to rescue the knight.

David Teniers the Younger’s The Magician Shows Carlos and Ubaldo the Whereabouts of Rinaldo (The search for Rinaldo) from 1628-30 is a small oil on copper painting in his series telling this section of Tasso’s epic. Here the wizard despatches the two knights to the Fortunate Isles.

At the start of canto fifteen, Charles and Ubaldo set off to retrace their steps with the wizard as their guide. The river takes them gently down to the sea, where a ship awaits. They board, and sail at miraculous speed past Ascalon and the mouths of the River Nile, westward through the Mediterranean, and through the Pillars of Hercules into the Atlantic Ocean. They eventually approach the Fortunate Isles, pull into a harbour, and the two knights disembark.

They spend the night at the foot of the mountain they have to climb to reach Armida’s garden with the captive Rinaldo. They set off at dawn, only to encounter their first obstacle: a fearsome dragon blocking their passage up the mountain. Charles draws his sword ready to slay the dragon, but Ubaldo waves a golden wand, a gift of the wizard, which drives it away.

Poussin’s The Companions of Rinaldo (c 1633-4) shows the two knights confronting this dragon. Charles stands in the centre with his sword ready, but Ubaldo behind him leaves his weapon in its scabbard and brandishes his golden wand instead. In the background at the left is the magic ship in which they sailed, and standing in its prow is the maiden who steered it.

Johann Friedrich Overbeck’s fresco of Ubaldo and Carlo free Rinaldo from Armida’s Castle from 1819-27, in the Casa Massimo, Rome, shows an interesting composite scene. To the right of centre, Charles and Ubaldo wield their sword and wand, and in the distance are Armida and Rinaldo in the garden on the summit. Amorini are playing with Rinaldo’s weapons, and his empty suit of armour has been cast into the undergrowth.

Next the pair have to face a lion, which is similarly dismissed with a wave of the wand. After that comes an army of animals they disperse readily, and Charles and Ubaldo are on the ascent towards the stretch of snow and ice they must cross before reaching Armida’s eternal Spring. Once up at the top, the two knights pause from their strenuous climb, slaking their thirst in a mountain stream. Grassy banks either side of the stream have a fine banquet laid out on them, and there are two naked young women cavorting in the water.

David Teniers the Younger’s Carlos and Ubaldo in The Fortunate Isles (1628-30) shows this moment, with the banquet laid out on a clean white tablecloth rather than grass. Surrounded by trees and standing proud on the skyline is Armida’s palace, their destination.

I only have this monochrome image of Charles-Alexandre Coëssin de la Fosse’s painting of Danish Warriors in the Garden of Armida from 1848. The two knights are dallying rather longer than their mission had intended.

Once Charles and Ubaldo can tear themselves away from these nymphs, they press on to the circular outer wall of the palace, which opens the sixteenth canto as they enter Armida’s garden.

In the eighteenth and nineteenth centuries, Armida’s garden appeared on all manner of products. This wallpaper designed by Édouard Muller in 1854 is now in the Philadelphia Museum of Art, while smaller images appeared on coffee cups and much else.

Tasso gives a brief description of the garden with its figs, apples and grape vines. Birds sing, and the wind murmurs softly. One bird speaks to the two knights, telling of the chaste and modest rose flower that springs virgin from its green leaves.

This passage about the rose was the inspiration for Marie Spartali Stillman’s exquisite watercolour of A Rose in Armida’s Garden from 1894, given by the artist as a wedding gift to a family friend.

Charles and Ubaldo then peer through the leaves and spot a loving couple, who they presume to be Rinaldo and Armida. The knight’s head rests in Armida’s lap. He then stands up and takes a crystal glass hanging at his side. Armida uses this as a mirror to adjust her hair, telling Rinaldo to keep looking into her eyes.

Tiepolo paints this clearly in his Rinaldo and Armida in Her Garden from 1742-45, now in The Art Institute of Chicago. It was originally hung in a special room dedicated to Tasso’s epic in the Palazzo Corner a San Polo in Venice, where it belonged to the noble Serbelloni family.

In Angelica Kauffman’s Rinaldo and Armida from 1771, the crystal glass is ready at Armida’s feet, and she is busy distracting him by sprinkling flowers over his head.

Francesco Hayez shows a variation in his Rinaldo and Armida from 1812-13. Anticipating the next part of Tasso’s narrative, instead of Rinaldo wearing the crystal glass at his side, his circular shield rests on the ground next to Armida. Charles and Ubaldo are shown peering from behind a tree trunk, safely in the distance.

Armida then kisses Rinaldo goodbye and leaves. Charles and Ubaldo see their opportunity and step out from the bushes, dressed in full armour. Ubaldo holds a highly polished shield up so that Rinaldo can see himself for what he has become, a woman’s dandy, not a warrior knight.

References

Wikipedia on Jerusalem Delivered.
Wikipedia on Torquato Tasso.

Project Gutenberg (free) English translation (Fairfax 1600).

Librivox audiobook of the Fairfax (1600) English translation (free).

Thomas Asbridge (2004) The First Crusade, A New History, Free Press, ISBN 978 0 7432 2084 2.
Anthony M Esolen, translator (2000) Torquato Tasso, Jerusalem Delivered, Gerusalemme Liberata, Johns Hopkins UP. ISBN 978 0 801 863233. A superb modern translation into English verse.
John France (1994) Victory in the East, a Military History of the First Crusade, Cambridge UP. ISBN 978 0 521 589871.
Joanthan Riley-Smith, ed (1995) The Oxford Illustrated History of the Crusades, Oxford UP. ISBN 978 0 192 854285.
Jonathan Riley-Smith (2014) The Crusades, A History, 3rd edn., Bloomsbury. ISBN 978 1 4725 1351 9.
Johathan Unglaub (2006) Poussin and the Poetics of Painting, Pictorial Narrative and the Legacy of Tasso, Cambridge UP. ISBN 978 0 521 833677.

I hope you enjoyed Saturday’s Mac Riddles, episode 352. Here are my solutions to them.

1: British sister of ANSI is Tahoe’s child of RSR.

2: Puzzle vault in the Da Vinci code contains Safari.

3: The sound of a liquid hitting a surface could be 1 or its parent.

The common factor

I look forward to your putting alternative cases.

One of the biggest penalties in using disk images has been their performance, particularly when they’re encrypted. Although no longer offered in Disk Utility, UDSP sparse images encrypted using 256-bit AES typically read and write as slow as 500/100 MB/s when mounted from an SSD delivering 4.7/4.9 GB/s. In contrast, UDSB sparse bundles can achieve close to that native speed.

macOS Sequoia brought a new type of disk image, Apple Sparse Image Format or ASIF, intended to deliver the high performance of sparse bundles, with their efficient use of storage space, in a single file that can be hosted on file systems beyond APFS. As this is now well over 18 months old, this article considers whether it has achieved those goals, and should become the preferred type of disk image.

Methods

Each test image was created using Disk Utility 22.7 (2510) in macOS 26.3.1 (a) running on a Mac mini M4 Pro, on its internal SSD of 2 TB. Performance measurements were made using the ‘gold standard’ method in my free Stibium on disk images of 100 GB nominal size. This writes and reads a total of 53 GB in 160 files ranging in size between 2 MB and 2 GB. As performance is likely to change with use of the disk image, the following sequence of events was used:

• Create disk image, which is mounted automatically, so unmount.
• Mount disk image, measure write speed, then unmount.
• Mount disk image, measure read speed, then delete the last 8 of 10 sets of test files, and unmount.
• Mount disk image, measure write speed, then unmount.
• Mount disk image, measure read speed, then delete all test files, and unmount.
• Mount disk image, measure write speed, then unmount.
• Mount disk image, measure read speed, and unmount.

These provide three pairs of read/write measurements:

1. for an empty, unused 100 GB disk image;
2. for a 100 GB disk image containing over 10 GB of existing files in addition to 53 GB of test files;
3. for an empty 100 GB disk image that had previously contained about 66 GB of test files that had been deleted.

Disk image sizes were also measured when unmounted, using Precize or the Finder’s Get Info (for sparse bundles).

The three types of disk image tested were RAW (UDRW), UDSB (sparse bundle) and ASIF (sparse image). Each was tested fully when unencrypted, and test 1 was performed on an image encrypted using 256-bit AES.

Results

The best and most consistent performance was achieved by UDSB sparse bundles, as expected. Their read speeds were 6.13, 6.12 and 6.19 GB/s, and write 7.62, 8.03 and 7.79 GB/s for the three separate measurements, and 5.09/5.23 GB/s read/write when encrypted. When first created, the sparse bundle only occupied 32 MB on disk, but by the end had grown to 3.99 GB even though empty.

The RAW disk image, formerly known as UDRW, also largely performed as expected. Read speeds were 6.09, 6.10 and 6.08 GB/s, and write 10.11, 9.86 and 10.11 GB/s. Initially it only required 5.78 MB on disk, rising to 621 MB at the end. However, its performance when encrypted was disappointing, at 2.84/1.58 GB/s read/write.

ASIF disk images were good, but also ran into problems when encrypted. Unencrypted read speeds were 5.99, 5.88 and 5.85 GB/s, and write 9.55, 8.93 and 9.64 GB/s. When encrypted, those fell to 2.82/1.72 GB/s read/write, no better than the RAW disk image. The image file size started at 26.8 MB on disk when empty and unused, and returned to 954 MB when empty at the end.

To confirm that ASIF performance when encrypted wasn’t an anomaly, I repeated that pair of tests on a MacBook Pro M3 Pro running 26.3.1 (a), and obtained similar results at 2.63/1.52 GB/s read/write, using a 10 GB ASIF image with one-tenth of the tests, giving 3.32/1.65 GB/s, and using Blackmagic, which gave 2.92/1.15 GB/s read/write. Although there is variation, they appear remarkably similar.

Test 2 results are summarised in the table above, for ease of comparison, and with the earlier results from macOS 26.0 below.

What has gone wrong with encrypted writes?

Although most of the test results in macOS 26.3.1 are very similar to those from 26.0, performance when using 256-bit AES encryption has fallen for all three disk image types, and most significantly in write performance for RAW and ASIF images, which have reduced from 4.3 to 1.58 GB/s (RAW) and from 3.9 to 1.72 GB/s (ASIF). The magnitude of those reductions is sufficient to have obvious impact on their use. Compared to native write performance using FileVault of 7.66 GB/s, those two types of disk image are pedestrian in the extreme, turning that blisteringly fast SSD into the equivalent of 20 Gbps over USB 3.2 Gen 2×2.

It’s possible that this dramatic reduction in encryption performance may have resulted from a change to address a vulnerability, but I’ve been unable to identify an entry in Apple’s security release notes that might correspond to such an event. I will repeat these tests once the update to macOS 26.4 has been released, in the hope it might be reversed.

Which disk image type?

When their folder-based structure is acceptable, UDSB sparse images remain the disk image type of choice, for their consistent high performance even when encrypted.

There is little to choose between RAW and ASIF disk images when a single file solution is required. ASIF images are portable to other file systems that can’t support APFS native sparse files, although curiously they too are flagged in APFS as being sparse files. As their sparseness isn’t dependent on APFS trimming habits, they are now an alternative that can be used on network storage and NAS. However, those able to use sparse bundles should continue to do so, particularly if using encryption.

During the 1880s Bruno Liljefors excelled as a wildlife artist, and was appointed head of the art school in Gothenburg, Sweden, in succession to Carl Larsson. But his personal life was in turmoil, and the 1890s were barren years when he often ran short of money.

His Common Snipe at its Nest from 1891 is a fine painting, but lacks the brilliance of his earlier works, with their loose backgrounds.

Hooded Crows (1891) captures these northern members of the crow family well, though.

Some of his finest paintings from this period are almost pure landscapes, such as his Hunting Geese (1896) with its superb mackerel sky.

He seems to have recovered his earlier form in the early twentieth century, as his new family grew around him. Spectacular paintings such as this Sea Eagle’s Nest from 1907 were often set around the fragmented coast of the Baltic. Although photographic technology was advancing rapidly, wildlife photography was still in its infancy: for instance, the National Geographic magazine had only published its first monochrome wildlife photos the previous year.

This is one of the many paintings that Liljefors made of a Winter Hare, here from 1910.

His later works include some substantial groups of birds, such as these Long-tailed Ducks in the Outer Archipelago (1911).

In 1917 Liljefors moved his studio to the village of Österbybruk near Uppsala, but continued to work from hunting lodges when necessary. Some of his landscapes became more post-Impressionist, as seen in this Autumn Landscape with Fox (1918).

His dedicated wildlife works didn’t weaken, as he concentrated on coastal wetlands, as in these Bean Geese Landing (1921).

Some of these late paintings have wonderful dialogues between the sky and water, as in these Geese in Wetlands (1921).

Liljefors never lost his fascination for the relationship between predators and prey, as seen in his Sea Eagles Chasing an Eider from 1924.

Eider on the Islet, painted in 1937, must be one of his last works from the coast.

Liljefors was also an accomplished gymnast, acrobat, and variety artist. With his two brothers, he formed the Manzodi Brothers, an acrobatic group who entertained Swedish audiences.

He died in Stockholm on 18 December 1939, a few months after the start of the Second World War. He had outlived his contemporary Anders Zorn by almost twenty years.

Reference

Wikipedia (in Swedish).

If there’s one thing I’ll remember macOS Tahoe for it’s brilliant engineering inside a shockingly flawed interface. Last week’s first Background Security Improvement was yet another example of that trend.

I had enthused about its predecessor the RSR three years ago, although it was sent to the naughty corner after an updated version of Safari told Facebook and other popular sites it wasn’t who they expected. After that trauma, most users shunned RSRs, and it seems engineers who dared mention them were strapped to the front of an F1 car and driven round until they recanted.

Thankfully, RSRs were only put on pause before being rebadged as Background Security Improvements or BSIs, an Orwellian turn of phrase that skilfully avoids the word update despite the fact that they’re still discovered, downloaded and installed by softwareupdated. Now I’ve had a chance to give a fair account of the first public BSI, I can consider what’s wrong with their current implementation.

Location

BSIs are controlled not in Software Update settings, but in their own section at the end of Privacy & Security. As such, they are the only macOS update there, and all others remain in Software Update where they belong. This misleads users, and Software Update reports that Your Mac is up to date when it isn’t, because there’s an outstanding BSI available.

Not only that, but users naturally assume that when Software Update settings have Install macOS updates disabled, no macOS updates will be installed automatically. Little do they realise they can still get a BSI without being asked.

BSIs are currently misplaced in System Settings, and their controls should be moved back to Software Update where RSRs were.

I fear the reasoning behind hiding BSIs among strangers in Privacy & Security was to ensure most Mac users would leave BSIs to be installed automatically. It’s no coincidence that, in addition to this hiding, the automatic installation of BSIs was enabled by default when upgrading to macOS Tahoe. This reeks of deliberate deception.

Control

There is a single on-off toggle provided, to Automatically Install BSIs. Apple explains that “if you choose to turn off this setting, your device will not receive these improvements until they’re included in a subsequent software update.” Thus the user is given a forced choice between macOS deciding when to install an available BSI, or not being notified about that BSI at all.

As with other macOS updates, the user must be given the option to be notified when a BSI is available, and to make their own choice whether and when to install it.

The alternative for users is to disable Automatically Install, watch for news of BSI releases, and, if they wish to receive one, to enable that setting, download and install the BSI, then disable the control again. For many Mac users, that appears to be the best option in the absence of better support.

Although the control is titled Automatically Install, its behaviour is different. When a BSI is found to be available, macOS doesn’t automatically download and install it, but waits for the user to click on the Install button, then to authenticate.

However, if the user isn’t aware that BSI is available, or chooses to ignore it, automatic installation does appear to occur without the user being informed until the Mac is just about to restart, and no authentication seems necessary after all.

This behaviour is the greatest deterrent to users, as it effectively means that their Macs could restart unpredictably with almost no warning, resulting in data loss and disruption to their work. That’s completely unacceptable, and will ensure many will disable BSIs as a precaution to avoid the possibility of data loss. This aversion could be addressed simply by allowing the user full manual control over whether and when a BSI will be installed.

Progress

Despite softwareupdated monitoring progress through the download and preparation phases, the user is shown an indeterminate progress spinner, rather than a progress bar, which would at least give better warning of the restart that is coming. Although much briefer than a full macOS update, a progress bar should be displayed for the download and preparation phases of a BSI.

Restart warning

All previous RSRs, and this first BSI, have required restarts to complete the update. Yet at no time during this BSI was the user told that would be necessary. A notification was displayed a few seconds before the restart, but gave insufficient notice for the user to make any preparations.

It’s essential that information given about the BSI states clearly if a restart will be necessary, and the user is given the same one-minute countdown provided in macOS updates. Bizarrely, the one place that a restart was mentioned is in the dialog to remove a BSI.

Information

Apple’s current support note on BSIs is woefully inadequate, as is obvious by the content of this article. What would appear to be additional information in the BSI settings, marked with the ⓘ Info button, isn’t informative at all, but provides the means to remove a BSI, which is at least an improvement on RSRs, which unaccountably hid removal in the About settings. A more appropriate button should be provided.

BSIs are also only currently covered in the US English version of Apple’s Platform Security Guide. All other localised versions, including British and Canadian English, still contain the outdated section on RSRs. Fortunately, as their content is almost identical, this is revealing rather than misleading.

Version numbering

Ignoring RSR and BSI version numbering, macOS has in recent years achieved clean and systematic version (and build) numbering, without the excesses of the past. By adopting a parenthesised letter as the identifier of a BSI, comparison is clumsy and prone to error. ProcessInfo.processInfo.operatingSystemVersion doesn’t contain a field for the BSI identifier, which is only offered as part of the full string in ProcessInfo.processInfo.operatingSystemVersionString. Version numbers like 26.3.1 (a) and build numbers of 25D771280a are irregular and unnecessary.

Recommendations

• BSI controls should be removed from their hiding place in Privacy & Security and put alongside all other macOS updates in Software Update settings.
• An option should be provided so that users are informed of the availability of BSIs without any obligation for them to be installed automatically.
• Behaviour of the Automatically Install button should be described explicitly to the user. Does it automatically install, and if so, in what circumstances will the user not be so informed?
• BSI download and preparation should be accompanied by a progress bar similar to that for a macOS update.
• When a BSI requires a restart to complete its installation, the user must be informed of that before they consent to the BSI being downloaded.
• When a BSI install is ready to restart the Mac, one minute’s warning notification should be given, just as in macOS updates.
• The BSI support note should provide full details, not a sketchy outline.
• The button to remove a BSI shouldn’t use the ⓘ Info symbol, but something more appropriate to its purpose.
• Apple’s Platform Security Guide should be updated in all its online versions. Is it really that hard to translate from US English to British English?
• Version and build numbering should be redesigned to be more consistent and better accessible in the API.
• Despite having over three years to get them right, BSIs are a worse mess than RSRs were in Ventura. This is a great shame as their technology is still brilliant, but their current interface is shockingly flawed in so many respects.

Reference

Support note about BSIs

When the Swedish artist Bruno Liljefors specialised in natural history painting in the late nineteenth century, he wasn’t the first to depict wild creatures and their surroundings.

It was probably Albrecht Dürer who pioneered faithful depictions, first in his meticulously rendered watercolour of this Hare in 1502.

Dürer followed that with some of the earliest botanical watercolours, such as this Primula from 1526. Despite those, few painters showed any interest in the genre.

Some of the Dutch artists who travelled to the Republic’s colonies were exceptions. This is Albert Eckhout’s Study of Two Brazilian Tortoises believed to have been painted in Brazil in about 1640.

Other painters of the Golden Age set faithful images of native species in more entertaining surroundings, as in Melchior d’Hondecoeter’s Concert of the Birds from 1670. But at that time, animal paintings were largely confined to domestic species.

The most famous of the early natural history specialists is John James Audubon, whose paintings of birds were turned into sets of prints. Among his surviving oil paintings is this of a Wild Turkey Cock, Hen and Young (Meleagris gallopavo) from 1826. Although clearly destined for use as an illustration, the setting is intended to appear more natural.

As the century progressed a new, objective style of painting developed in botanical and ornithological work in particular. Artists like Edward Lear illustrated multi-volume scientific publications classifying and describing different species.

Liljefors is one of the pioneers who painted rather than illustrated wildlife, and is revered today as one of the genre’s most influential figures. In this weekend’s two articles I show examples of his paintings that remain some of the finest artistic depictions of wildlife in the history of art.

Bruno Liljefors was born in Uppsala, in the east of Sweden, in the same year as Anders Zorn. He doesn’t appear to have been as precocious a painter, and started his studies at the Royal Swedish Academy of Arts in Stockholm four years later than Zorn, in 1879. He left the Academy after three years, and went to Dusseldorf to learn to paint animals.

In the early years of his career he travelled to Rome, Naples, and Paris, and was particularly inspired by the artists’ colony at Grez-sur-Loing, then dominated by the ideas and style of Jules Bastien-Lepage. Liljefors perfected his plein air painting technique, and became influenced by the Japanese woodcuts that were so popular at the time. He also aligned himself with the ‘Opponents’, a large group of Swedish artists who effectively seceded against the conservatism of the Academy.

During the early 1880s, Liljefors started to paint wildlife set in natural surroundings. Hawk and Black Grouse is a good example of these from 1884, showing a hawk attacking the gamebirds in a winter landscape. Although he had a deep affinity with his subjects, Liljefors was also a hunter, and many of his paintings explore the predator-prey relationship, as here. His hunting also provided him with dead specimens to use as models.

In 1885 he demonstrated his virtuoso skills in what he described as ‘five studies in a single painting’. Above is A Cat with a Young Bird in its Mouth, and below is A Cat and a Chaffinch. These were assembled from observations of living and dead animals and birds, and sketches, to produce composites that photography couldn’t match for decades, even in monochrome.

Following the tradition established by Dürer, one of Liljefors’ favourite species was the elusive hare. This page of Hare Studies from 1885 shows a tiny part of the image library he assembled, as well as the spring antics of hares. Liljefors also assembled his own wildlife park, with living and apparently quite tame creatures, including foxes, badgers, hares, squirrels, weasels, an eagle, eagle owl, and others.

The fox appears in many of Liljefors’ paintings, here A Fox Family (1886) in their role as predators, as they feast on an unfortunate bird.

Liljefors’ paintings are often painterly, such as in Jays (1886) which gives the impression of having been painted en plein air, in front of the birds and landscape.

Even for the modern amateur photographer, the fleeting form of Common Swifts (1886) is a great challenge. Set against a riot of flowers, these birds are the product of field observation, museum specimens, and careful studies, to make them look real.

Liljefors had deep insight into the behaviour of species he painted. The five Red-Backed Shrike Chicks (1887) shown here may not, at first sight, appear in keeping with their popular name, the ‘butcher bird’, but the chick at the left end of the branch is already taking an interest in a passing bee or fly. When a little older, it will catch it and impale the corpse on thorns in its larder.