I have a visionTek R9 280X flashed with HD 7970MAC's efi portion. It shows boot screen without any problem. However, it fails to boot my BootCamp windows 10, and gives black screen, while my second-slot working card geforce GT 120 gives error message "Video TDR Failure", and finally the system gets rebooted. I tried to resolve this by following suggestions on youtube, say, to unintall/re-install AMD drivers, set the wifi card to power saving mode, etc, but it still has this problem. The screen is black, and the system get rebooted until letting you change settings/do trouble shooting. The stock UEFI coming with the card works fine. Anyone has this issue? Any advice would be appreciated.
My configuration: Mac Pro 2009 with 2 6-core X5690 cpus, 32GB ram, flashed from 4,1 to 5,1. OS is High Sierra with 140.0.0.0 bootrom/firmware (installed using Mojave installer but without actually upgrading to Mojave as I still would like to use GT 120). BootCamp Windows 10 installed using DVD image (legacy bios) on a separate SSD.