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Grumply

macrumors 6502
Original poster
Feb 24, 2017
285
193
Melbourne, Australia
Hi guys,

Just picked up a 2019 Macbook Pro 15" the other day (my first ever laptop at 33!) and I've downgraded it from Catalina to Mojave 10.14.6 (for 32-bit software support).

I have the parts for a new 5,1 build en route (the base box has an HD 5770 and El Capitan), and I'll be using dual Radeon VIIs for the new build.

Now, as I understand it, the 5770 won't work with Mojave (due to not supporting Metal), but the Radeon VIIs will. However the Radeon VIIs won't give me a bootscreen, so I need an alternate method to get the machine from El Capitan to Mojave.

So I'm wondering if I can use Carbon Copy Cloner on the new Macbook, to clone the fresh install of Mojave 10.14.6 on to an APFS formatted SATA SSD. And then simply install that cloned SSD into the new 5,1 build (with the Radeon VIIs installed) and then simply boot from that?

Is that going to work for me?
 

Grumply

macrumors 6502
Original poster
Feb 24, 2017
285
193
Melbourne, Australia
Not likely, you need to update it to High Sierra first...this insures that the EFI is up to the latest version that Mojave needs. There is at least one thread on this that goes into more details. If I’m wrong @tsialex will correct me. The thread is this - https://forums.macrumors.com/thread...-bootrom-upgrade-instructions-thread.2142418/

Thanks for the heads up! I'll update the machine to High Sierra first (to get the BootROM updated), then move the cloned Mojave SSD over to the machine.
 
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