I'm looking for a description of what the firmware update actually does.

I have a MacPro (Desktop) 2010, and it's loaded with multiple drives, to be able to run every OS from Snow Leo to Sierra. This is the first I've seen an OS need to update firmware, and I'd just like to be sure I'll have no issue booting into the older OSes after this update.

Note: I've had this machine since it was new, mid-2010, and I've never seen a firmware warning when updating any OS.

  • Very good question. But my guess is that Apple just does not tell anyone and the reverse engineers are ever silent also. The latest firmwares were related to APFS (primarily at least). 10.10 to 10.12 did not exhibit bad symptoms after applying those updates to two machines I tested High Sierra with so far. If you avoid APFS you might also skip the firmware updates? – LangLangC Nov 8 '17 at 12:50
  • I suppose "the firmware" update depends on specific model, specific beginning version and specific ending version. There's a tool to make it easy to check versions and a nice paper showing the hundreds of combinations and explaining why your Mac Pro might have missed many versions since Apple shifted from stand alone updates to updating firmware when a system update and reboot happens. duo.com/about/press/releases/… – bmike Nov 8 '17 at 12:56
  • A lot of people may not even know that High Sierra includes a firmware upgrade for some hardware. The downvote could simply come from somebody assuming you are confusing an OS upgrade with a firmware upgrade – nohillside Nov 8 '17 at 16:37
  • Thanks patrix. I am a mod at Money.SE, where we give the simplest question the benefit of the doubt. Every board has its own personality, I suppose. – JoeTaxpayer Nov 8 '17 at 16:41
  • I swear I read somewhere that High Sierra locks itself to the motherboard of the machine that originally installed it, however after searching I can't find any reference, so maybe that was just in my nightmares? ;) – Fyrefly Nov 8 '17 at 18:53

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