Questions for anyone that knows the answers. I'm trying to understand exactly how the boot loader and NVRAM works so that I can try out OpenCore and I want to understand how I would rollback to non-OpenCore if it doesn't work out for me, and to understand exactly what i need to avoid to avoid bricking my NVRAM.
OpenCore is stored only on the EFI partition of your disk, nothing in the BootROM/logicboard/whatever.
Thank you for clarifying, sorry for simple questions...
Clover is the boot loader that can't be used and damage the Mac Pro NVRAM. OpenCore was designed to be used on Macs from the ground up and don't cause adverse effects.
Right so I interpret that to mean that Clover can and will write into the NVRAM, which is the BootROM (which is not on any disk), and that is how NVRAM can get corrupted that people have described on this forum thread. But you believe OpenCore should not make those kinds of mistakes in corrupting the NVRAM, so should be ok to try it out without too much concern about corrupting the NVRAM.
Does that include when I boot to MSWIndows? I read some post on one of these threads that there was some situations with MS Windows where it might have overwritten past some buffer limits in NVRAM or something and possibly corrupted it, even using OpenCore EFI windows install?
NVRAM is part of the BootROM, you can only backup it dumping the full firmware image from the SPI flash memory, using flashrom/ROMTools.
Thank you.
So a few more questions to help me figure out the best workflow to attempt this stuff... I need to understand exactly what the proper procedure would be to rollback out of OpenCore if I decide its not working for me.
So I think you're saying that if NVRAM gets corrupted because of a stupid boot loader (Clover), then might have to get some tricky software or maybe even hardware-level tools to restore the NVRAM back to a state where the machine can even be booted at all...ie...bricked. I'm not prepared to deal with that, and I definitely won't use Clover, so hopefully NVRAM wouldn't get corrupted any other way. If that is unlikely scenario with OpenCore, then I won't worry about it right now.
However, one other question.. Let's say I want to try OpenCore... Assume my system has 3 or 4 SSD's installed, any of which could be used for booting if I choose. Ok, so I have normal non-OpenCore Mojave installed on my primary drive. let's say I setup a completely separate drive with the OpenCore boot loader and install Catalina. Fine so far. And in those steps the NVRAM is changed (I think) to indicate that the mac should boot with OpenCore Bootloader which is on only one of the drives in the computer.
Alright, so I do that, I get it all working and play with it a while, but then for whatever the reason I want to pull it out and go back to my old non-OpenCore Mojave boot. I presume in that case I could not just pull out the OpenCore drive and boot up the machine, I would need to also configure the NVRAM to now look back to the original drive with non-OpenCore Mojave on it...then I'd be good to go back and could remove the OpenCore drive entirely and boot up with original Mojave, right?
what would happen if I pulled out the open core drive without reconfiguring NVRAM (if I have that right) to look back for the original Mojave non-OpenCore bootable volume? That's not really completely a brick because I could put the OpenCore drive back in, fix it and move on, but I just want to understand the ramifications of rollback before I try anything.
I think ultimately I will want the drive in drive bay #1 to have the open core boot loader and Mojave, and then I will have various other drives or partitions with Catalina, BigSur and Windows10, maybe even linux later. Sounds like rolling it back would simply be remove the bootloader and reconfigure the NVRAM and reboot, then it would be back to normal MacOS approach. yea?
And also, is there any reason to believe that my Mojave boot volume would act funny while booting under OpenCore...would it require hardware acceleration hacks and what not like is required for Catalina and Big Sur?
