If Apple is true to its annual cycle of operating systems, it will announce macOS 12 at WWDC next week. It has made it clear in its version numbering that the next major version of macOS will be 12, rather than 11.x, and a little speculation following firmware updates suggests which Macs it will support.

Some time between May and August, Apple likes to release firmware updates which come close to those required for the first release of the autumn/fall macOS. In a good year, the updates released in that period may remain current until well after that major release. Similarly, those Macs whose firmware isn’t updated during the May-August period are those which are most likely to be unsupported by that major release.

My current firmware analysis runs thus:

• All Macs with a T2 chip, and M1 Macs, have had firmware updates in macOS 11.4.
• iMacs up to and including iMac16 haven’t had a firmware update for several months, but from iMac17 onwards they have recently been updated in macOS 11.4.
• MacBooks up to and including MacBook8,1 haven’t been updated, but from MacBook9,1 they have.
• MacBook Air models without a T2 chip haven’t been updated.
• MacBook Pros up to and including MacBookPro12 haven’t been updated, but from MacBookPro13 they have.
• Mac mini models without a T2 chip haven’t been updated.
• Mac Pro models without a T2 chip, including the MacPro6,1, haven’t been updated.

Interestingly, most of those non-T2 models which were updated in 11.4 have standardised on a single firmware version number of 429.120.4.0.0, which is the first time that I have seen such uniformity across models. The only exception to those is the iMac19,1, with its oddball 1554.120.15.0.0, which is close, but not identical, to the EFI firmware in T2 models.

On that basis, macOS 12 is most likely to be officially supported on the following hardware:

• iMac Late 2015 onwards,
• iMac Pro,
• MacBook Early 2016 onwards,
• MacBook Air 2018 onwards,
• MacBook Pro 2016 onwards,
• Mac mini 2018 onwards,
• Mac Pro 2019.

That seems more brutal than usual, particularly with MacBook Air and Mac mini models, and it’s possible that the next round of firmware updates in macOS 11.5 might redeem some older models.

(I am very grateful to Pico for unravelling the firmware updates in 11.4, without which this speculation wouldn’t have been possible.)

Postscript

Several comments make claims about how long Apple is committed to support Macs with current releases of macOS, without citing any written statement which supports that claim. I’ve been unable to discover any explicit commitment by Apple in this respect. Indeed, the widespread belief that Apple is committed to supporting the last two major releases of macOS with security updates seems an unwritten understanding, not a written policy. If you know of any Apple document or recorded statement on these ‘policies’, then I’d really appreciate a link, please.

I wrote above that the cut-offs seen in firmware updates at present seem unduly harsh. However, our memories are short. When Apple made the transition to 64-bit, several recent Macs were caught out and orphaned very early. My Mac Pro 8-core (then the top-end Mac), which was sold between April 2007 and January 2008, was last supported by OS X 10.7.5 in September 2012, and those who bought the MacBook Late 2008, which was sold as late as January 2009, suffered the same fate, just over three years after many had bought them brand new.

Look back a little further to the last architecture transition, and you’ll find even younger orphans. For example, the iMac G5 20-inch, which was sold between October 2005 and March 2006, was last supported by OS X 10.5.8 which was released in August 2009, only just over three years after many were bought new.

I’m not saying this is what’s going to happen, but the changes in firmware version numbers are unprecedented and suggest that we might be in for a shock. Or there could be another explanation, of course.