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x99-a II big sur reboot on 2nd stage

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am trying to install big sur & i've read pretty much everywhere that x99 is out of luck with this release, but there also some lucky users who got it installed, so i was hoping if someone of the more experienced with opencore to tell where to look, or how to debug ?


below is my current efi along with the debug log from OC, if you need more info plz ask, thanx.



asus x99-a II

Intel i7-5820K

RX 590

iMac 1,1

OC v0.6.4




Edited by aufa333
  • 2 months later...

X99 have problem with broken NVRAM on Big Sur, so on second stage will be always reboot. To make it work you need to bring u'r hardrive/ssd/nvme on another machine and install it in there. After that you just replace u'r opencore boot loader on u'r hardrive/ssd/nvme EFI and it wil work on x99 machine.

I just went through this - 



I ended up doing what @dedeendium suggested above - install and configure fully on another PC and install OC/EFI for X99-A II.


You should be able to use what I posted in my thread since only difference is the GPU - RX590 should be supported out of box.


Good luck~

Edited by xthunder
  • 3 weeks later...
On 2/15/2021 at 4:57 AM, mickeyd453 said:

or just install Catalina, get emulated nvram working and then perform an upgrade from Catalina to BS

How I can check that I get the emulated nvram? I have a full function Catalina of my Asus X99-A-II

  • 5 weeks later...
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