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Downgrade to Mojave, including Firmware
- Thread starter Dave_O
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Not only that, but if you have a newer 2016+ rMBP, macMini / MacBook Air 2018+, or iMac Pro, the T2's BridgeOS gets updated as well.
If you attempt to do so, at worst you will render your Mac (if it's one of the ones above) unbootable.
eclecticlight.co
At best if you pick the wrong older Mojave version to restore, like if you have a backup from before one of the Mojave Supplemental updates, you might wind up with an update that endlessly can't install because the updater doesn't recognize the Catalina firmware.
It's kind of frustrating to see all the junior Mac help websites parrot the steps to doing Catalina -> Mojave downgrades without mentioning this potentially fatal issue.
If you attempt to do so, at worst you will render your Mac (if it's one of the ones above) unbootable.
Don’t try reverting a T2 to older firmware
If you’ve been running pre-release firmware on your Mac’s T2 chip, trying to revert to a release version could brick it.
eclecticlight.co
At best if you pick the wrong older Mojave version to restore, like if you have a backup from before one of the Mojave Supplemental updates, you might wind up with an update that endlessly can't install because the updater doesn't recognize the Catalina firmware.
It's kind of frustrating to see all the junior Mac help websites parrot the steps to doing Catalina -> Mojave downgrades without mentioning this potentially fatal issue.
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No, the Catalina firmware is backwards compatible. What build of 10.14.6 is installed on your computer?
Try downloading a full Mojave installer from the App Store. That will include the update.
Apple's had some network issues for the last week or so, unfortunately. This may also be why your supplemental update is failing.
You can't re-install old firmware, but you CAN still run Mojave on a Mac that has been "touched by" Catalina.
I can "dual-boot" my 2018 Mini from either Mojave or Catalina.
I DID NOT install Catalina onto the internal drive.
Instead, I installed it onto an external USB3 SSD. Boots and runs ok from that.
But Catalina offers me nothing, and "takes much away" (all the 32-bit apps I use and prefer).
I'll not be upgrading "beyond Mojave" any time soon.
Perhaps not for 5-6 years, if I can get away with it.
I can "dual-boot" my 2018 Mini from either Mojave or Catalina.
I DID NOT install Catalina onto the internal drive.
Instead, I installed it onto an external USB3 SSD. Boots and runs ok from that.
But Catalina offers me nothing, and "takes much away" (all the 32-bit apps I use and prefer).
I'll not be upgrading "beyond Mojave" any time soon.
Perhaps not for 5-6 years, if I can get away with it.
I just bought a late 2018 Mac Mini new from B&H Photo. It's has an i3 processor. It came with Big Sur installed. I need to run Mojave. Can this be done? I know the Late 2018 Minis did come with Mojave.
Have Mojave, Sierra, High Sierra and El Capitan on external SSD and boot from them whenever needed. Mountain Lion still on the internal Fusion Drive of my old 2013 iMac (the one with the FD was formatted with 128 G of FD). This iMac boots now with Catalina on another SSD. Works flawlessly until now but it's the end of the road for this i5 machine. BTW, no problem, zero, nada, with it since purchase in 2013.