I have a B2 post error on bios after uninstall AMD drivers with DDU and reboot.

My GPU is a Club 3D HD7970, mainboard Asus Maximus V Formula and latest bios version available (1903).
OS: WIN10

I tryed to reset mainboard bios multiple times, unplug all except card, and plug gpu to other PCIe slot but error persist.
I have also tryed to plug gpu in other pc and is working well.

When i unplug HD7970 and use onboard graphic all working and W10 show me gpu under device manager, but if i try to install drivers for gpu system go in blue screen with exception: SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (atikmdag.sys).

I know HD7970 does not have UEFI bios, and B2 q-code ("Legacy Option ROM Initialization") error looks like some issue in bios post for non UEFI section.

On my BIOS > Advanced and PCIe config if i set onboard graphic i see my HD7970 and 16X PCIe plugged, but when i switch to PCIe graphic on startup i get only a B2 Q-CODE.

How i can resolve?

Thanks in advance.