Why is my Mac’s firmware version wrong, and what to do about it?

So you’ve checked the version of firmware in your Mac, either in System Information or using a utility like SilentKnight, and it doesn’t match that expected for that model and version of macOS installed on it. This article explains how that can happen, and what you can and can’t do about it.

For many years now, Mac firmware has only been updated when you install or update macOS on that Mac, and the version of firmware installed should match the version of macOS. The update or install doesn’t have to be to its internal storage, though: when you update or install a newer version of macOS to an external disk, that should also update your Mac’s firmware. That doesn’t apply to macOS installed in virtual machines, though, and merely downloading macOS can’t change the firmware either.

Version higher than expected

Sometimes, the mismatch in versions shows that your Mac has a higher version number than expected. That’s only going to occur for one of two reasons:

  • Your Mac has installed a newer version of the firmware. This often happens if you install a beta-release of macOS, or could happen after service to your Mac.
  • Your Mac has installed a spurious version of the firmware, such as malware. You should be able to check that in Intel Macs running High Sierra and above using eficheck as described below.

Don’t forget that when you’ve installed macOS to an external disk, that can update its firmware. If your Mac boots from Catalina on its internal disk, but you tried out Ventura on an external disk, then its firmware will have been updated to that for Ventura. With the exception of Apple silicon Macs, firmware should never be downgraded, as its installer doesn’t allow that to happen.

Lower version, Intel without T2 chip

Almost all problems with older and outdated firmware occur on Intel Macs without T2 chips, and certain models are notorious for this, like the iMac Retina 5K 27-inch Late 2015 (iMac17,1). The most common reason for failure to update their EFI firmware is because the internal storage is non-standard, either replaced, or unusual for that model. In the case of the iMac17,1, it’s largely confined to the more expensive BTO options with internal SSD storage, and in other cases it has been seen when the original internal storage has been upgraded, or replaced following failure.

Before going any further, if the Mac is running High Sierra or later, check its EFI firmware integrity using the eficheck tool. Open Terminal, and in its command line type
/usr/libexec/firmwarecheckers/eficheck/eficheck --integrity-check

Once it completes, you should see a response like
EFI Version: MBP141.88Z.F000.B00.1909131925 (Boot ROM Version:
Primary allowlist version match found. No changes detected in primary hashes.

In the first line of the response, this gives the Mac model (MBP141 = MacBook Pro 14,1), the major version (F000), the minor version (B00), and the build datestamp of that version (= [20]19/09/13 19:25). If that reports a problem, save the result immediately and contact Apple Support soonest, ready to quote those results to them.

Fuller details about eficheck are given in this article.

Provided that eficheck is happy, your Mac isn’t in imminent danger. All you can do is install or update macOS on a disk inside or attached to it, to see if that will update its firmware. The article linked to above describes the lengths to which some have gone to try to update their Mac’s firmware. The most you’ll probably want to do is contact Apple Support or book your Mac in to an Apple store.

Lower version, Intel with T2 chip

Macs with a T2 chip have two sets of firmware: EFI firmware for the Intel processor, and iBridge or BridgeOS for the T2 chip. Although it’s now exceptionally rare for these not to update properly, when they do the T2 chip’s firmware can be revived by connecting it to another Mac running Apple Configurator 2 (free from the App Store) using a USB-C cable. This procedure is described in full detail in Configurator’s Help book, where Apple states that “A revive updates the firmware on the Apple T2 Security Chip. A revive is designed to not make any changes to the startup volume, the user’s data volume, or any other volumes. User data may be retained if recoverable.”

The eficheck tool isn’t available on these models, and I’m assured that reviving firmware using Configurator updates both EFI and T2 firmware together. However, firmware problems with T2 Macs appear to concern the iBridge firmware rather than EFI.

If your T2 Mac can’t update its firmware properly, and Configurator doesn’t help, you should contact Apple Support or book your Mac in to an Apple store.

Lower version, Apple silicon Mac

M1 and M2 Macs are completely different, and don’t have any EFI firmware at all. Although the version number of iBoot is conventionally given for their firmware, in fact iBoot isn’t actually their firmware. The Secure Boot process used in Apple silicon Macs ties firmware and iBoot together, and should ensure that the firmware installed matches the version of macOS, unless the firmware is more recent (as explained above).

Updating both firmware and recoveryOS (in its own container on the internal SSD, not paired Recovery) can be performed using Apple Configurator 2 to revive that Mac, much in the same way as for T2 models. This is described in full detail in Configurator’s Help book, where Apple states: “A revive updates the firmware and updates recoveryOS to the latest version. A revive is designed to not make any changes to the startup volume, the user’s data volume, or any other volumes. User data may be retained if recoverable.”

What is very different with Apple silicon Macs is that their firmware can be downgraded by Configurator, as well as upgraded (by installing more recent macOS). For example, if you upgraded your M-series Mac to Ventura, its iBoot version will have changed to 8419.41.10, as it will be in Monterey 12.6.1 or Big Sur 11.7.1, which install the same firmware. If you wanted to revert that Mac to Monterey 12.6, complete with its older iBoot and firmware, then you could download the IPSW image for 12.6 from Apple and restore that to your Mac using Configurator. That will return it to factory fresh condition, with 12.6 and its firmware running.

However, as Apple points out: “A restore updates the firmware, updates recoveryOS to the latest version, and erases and installs the latest version of macOS on your internal storage. When this process is complete, any data on any internal volumes is unrecoverable.” You then have to personalise the Mac as if it was new again.

If you have any problems with Apple silicon Mac firmware, contact Apple Support or book your Mac in to an Apple store.

Further investigation

More recent versions of macOS, since Big Sur, provide detailed information about what has happened during macOS updates, in the text log at /System/Volumes/Update/restore.log. If you suspect that there may have been a problem with the firmware installer during an update, you may find information and error codes that provide clues as to what happened. However, this file is very large and unwieldy. Good luck!