Catalina - how to revert EFI-Update?

[TomMuc]

Hi everyone

I installed Catalia on a late 2012 Mac mini to try it out. Unfortunately, Apple also installed new EFI firmware without asking during the installation. Since I prefer Mojave, I switched back to it, even without APFS.

Now I get an annoying warning every time that the hard drive (SSD) is not compatible. This is definitely due to the Catalina EFI, which is not really compatible with Mojave. It's just a minor flaw, but it annoys me immensely.

Apple is increasingly becoming the 1984 they used to warn about in their ads. How can I get the old EFI back? It would be great if one of you could help me with this.

Kind regards,
Tom

 

[Grumpus]

I installed Catalia on a late 2012 Mac mini to try it out. Unfortunately, Apple also installed new EFI firmware without asking during the installation. Since I prefer Mojave, I switched back to it, even without APFS.

This sounds like an APFS version mismatch to me. If the disk was erased during the Catalina installation, and then not re-erased using the Mojave installer, you'll see a compatibility warning every time you log on to Mojave. The warnings might, indeed, be merely cosmetic, but I wouldn't count on that. To avoid possible data loss, my advice would be to back everything up and then re-install Mojave, being sure to erase the disk using the Mojave version of the Disk Utility app. You can recover your files and settings from the backup using Migration Assistant during the re-installation.

 

[TomMuc]

thanx for your reply grumpus. but the disk/ssd running mojave is hfs+ formatted. but even if totally erased and fresh mojave install there comes a tiny apfs partion by itself. and this comes from the catalina efi and is the reason i want to roll back to the older efi version. i'm not looking for all kinds of workarounds - just for a way to get the old efi back.

cheers
tom

 

[Grumpus]

EFI partitions are formatted as FAT32, not APFS. Please run Disk Utility, selecting View -> Show All Devices from the menu, and post a screenshot of the window.

 

[TomMuc]

hi grumpus.

nope - theres always a new apfs partition when mojave is fresh installed even after low-level format of the whole disk/ssd. the only question i have is how to roll back the efi(rom) to the state before catalina.

thanx
tom

 

[Grumpus]

Again, the EFI partition is FAT32, not APFS. It's also not shown in the GUI-based Disk Utility app (and almost certainly not your problem anyway). You can open a terminal and run diskutil listto see it. Assuming you have a single disk, running sudo diskutil mount disk0s1 will mount it as /Volumes/EFI, after which running diskutil info disk0s1 will prove to you that it's a FAT32 partition.

If you erase the physical disk (the top-level device) using Disk Utility and then reinstall Mojave, the EFI partition will be recreated. I know of no other (practical) way. If you do decide to reinstall, there is absolutely nothing to be gained by jumping through the hoops needed to install Mojave on HFS+, given that you have a SSD.

Without seeing your disk layout I can't offer any further help, but good luck.