Why RX5700 black screen on big sur? help

[GhostRaiderMX]

I also had the same issue. MSI Z390 Gaming Plus motherboard with RX 5600XT and OpenCore. Got black screen after Big Sur install.

I had 2 solutions to this problem. Either disable Serial port in BIOS or disabling OpenCore debugging information. I chose to disable OpenCore debug information.

Use OpenCore 0.6.3+ RELEASE version (Not Debug Version)
Then in config.plist remove boot flags "-v debug=0x100 keepsyms=1" but make sure to keep "agpmod=pikera".
Then in Misc > Debug, set these to:

AppleDebug = False
ApplePanic = False
DisableWatchDog = True
Target = 0

Then reboot, clear NVRAM and select macOS. After that it boots perfectly with no black screen. At least in my case.

 

[Labicudo]

Thanks GhostRaiderMX, I had the problem with my Gigabyte Z390 M Gaming and RX 5700XT. Disabled serial port in bios. No more black screens.

 

[julioTele]

My motherboard is MSI-Z390-GAMING-PLUS,and cpu is i7-9700k，graphics is RX5700，it works all well on catalina.But on big sur,my monitor get black screen forever.Only the first time after installation, the monitor works well. I nearly try everything I can find , the below is what I try.
1. change the smbios to MACPRO 7,1, and use adgpmod=ignore
2. use the smbios imac 19,1 and use adgpmod=pikera
3. upgrade the oc、lilu、WEG version to the newest.
BUT none works. On ******, someone have the same experience, but at last he change his motherboard to asus. I cannot change my motherboard right now. So I doubts if the nvram have something with this problem? Wish someone can give me some advice. Thanks a lot.
The attachment is the efi I use right now, oc version is 0.6.1. Wish it can give you some dirctions. Thanks again.

SOLVED
1 - Mount Efi
2 - Edit Config.Plist With ProperTree
3 - Go to NVRAM ---> Add ---> 7C43611-AB2A-4BBB-A880......... ---> boot-args ---String
4 - Add: agdpmod=pikera
END !!!! Video OK!!!