It seems like macOS Big Sur fixes error 12
I managed to get my Windows 10 to work with the eGPU in the past out of dumb luck. It would work for a couple of days and then it would break eventually at some point for no apparent reason (even unplugging and plugging a usb device would break it). So last June I gave up with boot camp.
Coming yesterday I booted into Win10 without the eGPU attached and updated to 2004 - 20221.1000. Then tried with the eGPU, same all. Black screen if booted with the eGPU attached, error 12 if hot plugging the eGPU after boot.
Then I went into macOS and update to beta 6 of Big Sur (this is what is get fetched by apple when you enroll your mac to public betas). I installed the macOS without the eGPU attached. After installation both macOS and Win10 would work with the eGPU plugged in before booting the machine up.
Then I update Big Sur to beta 8 (without) the eGPU and Windows keep working just fine.
I don't know whether I just struck the perfect combination of resource allocation once again or whether Big Sur actually fixes things egpu-wise. I am just letting you know guys.
For me it stopped working after updating to Beta 7/8. Was working fine on Catalina and up to Beta 6. So there are definitely some changes going on.
I already wrote down the things I tried to fix it here.
Anyone get their egpu working after installing Big Sur beta 8? Mine was working on Catalina but stopped after I installed and immediately upgraded to the latest public beta of Big Sur. All I get constantly are code 12s...
@erik_tank, did you manage to solve your issues? Did you need to downgrade iBridge firmware in order to make it work?
I ended up doing a catalina internet restore but I don't think that downgrades the T2. I updated to Big Sur public beta (6) and ended up using a 1903 v1 iso from some other post in these forums... as long as I block windows updates I'm fine. Trying to update and then copy the pci.sys file from a backup just BSOD on me. Not sure what I'm missing on that when others report success. But at least my 1903v1 works fine right now. I haven't gone past beta 6... seems stable enough to me I guess.
@erik_tank, Some of the latest 2004 versions do not like PCI.SYS swap. I experienced the same thing so it's best to use 1903 V1. The firmware updates can change preboot behavior so it's possible to effect eGPU initiation and detection in Windows.
@erik_tank, @itsage Yeah, that's what I'm doing as well. BSOD on pci.sys swap on latest builds, so I had to resort to using 1903. Hope new versions of Windows will fix the damn support of AMD eGPU cause it's getting ridicolous.