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I've read quite some posts reg. eficheck; in itself it doesn't seem too "worrying" (for security reasons it's probably quite useful, but that's a bit off-topic here)

I found this very interesting document here, which I unfortunately only understand partly (I suppose I could grasp it to 99%, but it'd take me 2 days - and maybe some others here already read this): https://duo.com/assets/ebooks/Duo-Labs-The-Apple-of-Your-EFI.pdf In there it says: "[...] there appears to be another level of checking that takes place within Apple’s pre-boot EFI environment that prevents rollback to an older version of EFI. "

After I update to High Sierra, will I be able to roll back, incl. the older firmware - just in case the newer firmware reveals some disadvantages later on?

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  • I wanted to make a general answer, but 2009 MacPro is no longer supported and the 2010 are probably next up for end of support. That makes things a little harder. It's possible Apple will keep patching that firmware and it's possible you might need someone to help with "aftermarket" updates or revert tools. For shipping / supported Mac - the answer will be "upgrade" and contact Apple when things don't work.
    – bmike ♦
    Sep 30, 2017 at 12:26

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In general, no. Apple doesn’t release tools to reverse an EFI update publicly. In general, these aren’t needed since the drivers for GPU and other functional aspects of running the system exist at the OS level which you can revert to freely. Also, EFI updates now arrive with normal OS updates, so most people get these updates when you apply normal updates and not needing to run a separate EFI update.

Technically, Apple service providers can get access to tools to revert firmware but that is more geared to when an update hangs as opposed to there being a known regression.

Known regresssions generally are resolved with a newer patch on top, always advancing EFI versions as opposed to reverting.

Now - hardware like the Mac Pro (Early 2009) may have other worries due to being classified Vintage and Obsolete products as defined by Apple: https://support.apple.com/en-us/HT201624

Also - there is a nice paper by some long time Mac administrators that work for a security firm now with research on EFI updates and what happens without a check and users being shown when they are down level:

It's getting a fair bit of mainstream coverage - but the headlines there are a bit click bait / overblown in my experience so far. The risk to home users is very low and EFI is generally only needed to exploit systems when they are already running 10.12.6 and have all updates applied and you can grant local physical access by a skilled technician of the hardware that's being attacked.

In specific, the Mac Pro 5,1 is listed as never having an update in the DuoSec research paper - so all this might be a moot point if all you care about is Mac Pro 5,1.

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  • Thanks bmike - do you actually know, whether this is indeed the case for High Sierra as well, or is it just generally the way this is handled? I was guessing (or assuming, after reading this PDF) with HS / eficheck this might have changed.
    – MickyB
    Sep 30, 2017 at 12:20
  • I have no detailed knowledge of the specific version of firmware for MacPro 5,1 and what happens when you install it on that specific HW. I do know Apple is evangelizing this - they want everyone to start being aware of firmware levels and pushing everyone to keep up to date. I expect the need to revert will be almost NIL as they will push fixes since every Mac out there with default settings will complain once a week if they are down level asking for an update. I'll edit my post with some research on this @cinegraphy
    – bmike ♦
    Sep 30, 2017 at 12:25

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