Firmware and the iMac Retina 5K 27-inch Late 2015 (iMac17,1): a hardware fault?

Have you got an iMac Retina 5K 27-inch Late 2015, model iMac17,1? Has its firmware updated as expected, or has it remained steadfastly stuck at (or similar)? If so, I may have news for you later this week, and invite you to help me unravel just what’s going on with that model, at last.

It’s been almost a year since many iMac17,1 users upgraded to Catalina, or installed the corresponding Security Update to High Sierra or Mojave, which should have updated their Mac’s firmware to version A lot, possibly even a majority, didn’t update correctly, and have failed to with every subsequent update they’ve had installed.

Earlier this year, with your help, I conducted a survey here, as a result of which I discovered that this was a very common problem specific to the iMac17,1. I reported it to Apple via Feedback, with the evidence I had gathered, and haven’t heard anything back. Not in six months. Several of us suspect that the reason that some iMac17,1 systems update their firmware without bother, and others don’t, is because they have different logic boards. I now have information which suggests that explanation is feasible, and have a way to find out.

Some time ago, I looked at how we might investigate a link between the logic board ID and success/failure in updating firmware, but I couldn’t find an easy way to discover that hardware ID. Thanks to work by Mr Macintosh, I now have a method which is extremely simple, and information which he has already gathered that suggests this is likely, as he has been quietly collecting logic board IDs for different models of Mac.

For the majority of models of Mac, there’s only a single logic board ID: the original, in that model’s first release, and that doesn’t change in later production. There are two models which have proved an exception, the iMac Late 2009, or iMac10,1, and the iMac17,1. Whereas the iMac10,1 has three IDs which are very similar, suggesting a series of minor revisions, those for the iMac17,1 are completely different – according to Mr Macintosh

  • Mac-65CE76090165799A
  • Mac-DB15BD556843C820
  • Mac-B809C3757DA9BB8D

It’s tempting to speculate how a single model came to have three such different logic board IDs. I think that we can safely conclude that some iMac17,1 systems are quite different from others, something which could easily be reflected in their ability to have their firmware updated.

That’s where you come in, if you have one or more iMac17,1 systems. If (and only if, please) yours is running one of the following versions of macOS, I’d like to hear from you:

  • 10.15 Catalina, any version
  • 10.14 Mojave, with Security Updates from 2020
  • 10.13 High Sierra, with Security Updates from 2020.

If yours hasn’t been upgraded beyond Sierra, then it’s still likely to be running an older version of firmware.

If your iMac17,1 should have had its firmware updated, I’d like to know the current version of its firmware and its logic board ID, please. Easy ways to check the firmware version are using my free apps SilentKnight or LockRattler, or you can view that as the Boot ROM Version listed in the Hardware section of System Information.

Finding out the logic board ID in that Mac is now simple using the latest version (1.0b8) of my free app Mints. Click on the Get Mac Info button and it will be listed in a window as the Logic Board ID.

When you’ve found those two out, whatever the firmware version, please post the result as a comment here, or send it to me by email at h [dot] oakley [at] Note that Mints also reports your Mac’s serial number: please don’t post or send me that, just the firmware version and logic board ID.

My suspicion is that those iMac17,1 systems which fail to update their firmware have the same one or two logic board IDs, and those that update successfully have different IDs. If that’s true, it strengthens the case that this is a hardware fault, and not “normal” or “correct” as many users have been told by Apple Support.

Thank you for your help: as soon as I have sufficient reports to confirm or deny my suspicion, I’ll post my analysis here.