LoginLast Week on My Mac: How Apple silicon came so quickly
Everyone knows that January, the first month of the New Year, is named after Janus the Roman god of transitions. There are a couple of problems with that, as neither the Romans nor the Greeks started the New Year in the middle of winter, not when they could help it. Although it’s true that the Romans named the first month of the year Ianuarius, according to some ancient almanacs that wasn’t in honour of Janus, but of Juno. The more modern assumption that January, now a winter month, was named after Janus, classically depicted as a duality, makes a more plausible story. Janus characteristically has two faces on a single head, one looking backwards to the old year, the other looking forwards to the new: Ianus Bifrons in Latin.
So he appears in Anton Raphael Mengs’ wonderful fresco in the Vatican’s Camera dei Papiri, The Triumph of History over Time (1772). You’ll no doubt recognise Father Time with his long grey beard and scythe in the foreground, behind whom History is busy keeping records. She looks up to the fresh new face of Janus, as the old face looks away to the right.
This New Year I’d like to cast us back to September 2016, when macOS 10.12 Sierra had just been released, six years after Apple had released the iPhone 4, the first with its own A4 chip. Just four days before Sierra, Apple released the iPhone 7, with its two P and two E cores, making it the first Apple silicon design to adopt Arm’s big.LITTLE architecture. Maybe some engineers have been working on a prototype Mac using an A11 (to be released in the iPhone 8 the following year), and the specifications for the first generation of Arm-based Macs are being finalised.
To get from Sierra running on Intel 4-core Skylake processors to macOS 11 running on 4-core M1 chips, there’s a long list of changes to be made, including:
- a modern file system to replace HFS+, designed for SSDs, with support for containers, volumes, sparse files, snapshots, and more;
- running 64-bit code throughout;
- macOS to run from a signed system volume on a mounted snapshot verified by a tree of hashes;
- replacement macOS installers and updates to maintain macOS in the SSV;
- a firmlinked Data volume to be writeable by the user, with FileVault implemented using hardware encryption;
- a secure enclave;
- a fully secure boot process in custom firmware without using EFI.
Engineers have already been working on those, and the first release of the new file system, APFS, is intended for the following year, when intermediate hardware based on the A10 in the iPhone 7 will be released as the T2 chip, providing a secure enclave, hardware encryption and a firmware development platform. The problem now is how to complete the rest of the transition, so enabling the first Apple silicon Macs to be released by the end of 2020.
Although four years might seem a long time, here’s a timeline for those changes:
- 2017: APFS release, first T2 Macs.
- 2018: completion of major APFS features, transition to 64-bit code.
- 2019: 64-bit only, intermediate boot volume group without SSV.
- 2020: SSV and boot volume group, replacement install and update, firmware for a full hardware release late in the year.
- 2021: improved efficiency in macOS updates, paired Recovery volume.
And that’s exactly what happened from macOS 10.13 High Sierra to 12.0 Monterey.
However and whenever those changes were to occur, it was going to be a demanding period for Apple’s engineers, third-party software developers, system administrators and users alike. Was there an alternative that could have completed the same transition at a slower and more comfortable pace?
Merging the changes for any adjacent years would have resulted in at least one upgrade that would have made impossible demands. For those who have wanted major versions of macOS to be released every two years, the consequence would have been that macOS 11.0 would have been released just a few months ago, and only now would we be trying out our new M1 Macs. The next time that someone wishes that macOS had been upgraded at a slower pace over those years, remind them how that would have delayed introduction of Apple silicon Macs by around four years.
With that, it’s time for Janus to swap faces, and look forward to the coming year.
