Could this fix firmware updating in the iMac Retina 5K 27-inch Late 2015 (iMac17,1)?

If you’ve not been following the saga of failed firmware updates, you should still be aware that these updates now only ship as part of macOS installs and updates, and that some users have found that they won’t install on their Macs, leaving them with out-of-date firmware despite keeping macOS updated.

In the past, this has been a problem in many Macs which have had their internal storage replaced, particularly with an SSD. One model which has proved particularly troublesome is the iMac Retina 5K 27-inch Late 2015 (iMac17,1). Despite reporting to Apple the large number of iMac17,1 computers which have been troubled by this, I’ve had no response. That was nearly a year ago now. Many users have contacted Apple Support, only to be told one of several different stories.

These include the claim that this model didn’t need the updates, which is patent nonsense as Apple has continued to provide them since the release of Catalina, when the firmware version in that model was It’s now 429., and those still stuck in the past are noticing problems with their Macs running such old firmware.

Apple has apparently examined and tested some iMac17,1 computers which stubbornly refused to update. Several users have been told that ‘engineering is working on it’. I conducted a survey here to try to discover if it was associated with a particular version of logic board, which it isn’t. After a lot of work by many users, we’re still left with the same problem, and no word from Apple as to what’s wrong with all these Macs, or whether Apple can or will fix them, or just hopes that they’ll fade quietly into obsolescence.

Several users have reported recently that their affected iMac17,1 computers have internal NVMe SSDs, most supplied from new by Apple. On replacing those particular SSDs, the Mac is able to update its firmware normally again. From the information I gathered in the survey here, I believe that the firmware update problem extends to iMacs which don’t have an NVMe SSD, rather a hard disk or Fusion Drive, but I haven’t sufficient information to be categorical about this.

I’m very grateful to Roman, who has written me a long email explaining all that he has tried to resolve the problem of his iMac17,1 and its out-of-date firmware. As he has now successfully updated to the current version, he’s keen for me to pass on his experience, in the hope that it might help you deal with your iMac17,1.

Roman systematically tried re-installing macOS from 10.11.6 right up to Big Sur, without any success. He then extracted the firmware updater from each of those updates, and just installing those, again going from macOS 10.11.6 up to 11.1. The firmware remained stuck at He repeated installing macOS from a USB memory ‘stick’, which also failed to update the firmware.

As his iMac contains a 256 GB NVMe SSD, he then devoted his attention to that. He first used a PartedMagic USB stick to wipe the internal SSD using the ATA sanitize commands, a procedure he has used on many other Macs, but he was unable to ‘unfreeze’ the internal SSD.

His final step was to strip his iMac down – not an easy procedure, and certainly not for the ‘ordinary user’. He next tried replacing the internal SSD with an OWC Aura 2 NVMe SSD, but that didn’t help. So he then removed the internal SSD, and connected a hard disk to the SATA port on the logic board. When he installed macOS 11.1, the iMac’s firmware updated to 429. at last.

With the firmware finally up-to-date, he removed the hard disk, replaced his NVMe SSD, and the iMac worked fine. It has now updated – without the need for further hardware surgery – to version 429. with the recent update to macOS 11.2. As other users have experienced, once their iMacs undergo firmware update to or later, they continue to update normally with future macOS releases.

Few other users with iMac17,1 computers are likely to be able to swap their current internal storage for a hard disk in the way that Roman did. However, this would be relatively cheap and quick for Apple to deliver through its Authorised Service Providers.

My question is whether all those iMac17,1 computers which have failed to undergo firmware update have NVMe SSDs fitted by Apple, or whether others do have a hard disk or Fusion Drive?

I hope that we may be nearing a solution at last.