AtomBiosPatcher

Load a custom AtomBios to unlock graphics card features. Currently this tool only supports loading to the ACPI VFCT table. Probably will only work on pure-UEFI APU only systems

Windows

If it appears that the ATOMBIOS hasn't changed, uninstall the GPU from device manager (keep software), reboot and it should automatically install back. During all these steps make sure you boot with AtomBiosPatcher (and in the future too so it doesn't get overwritten)

Credit

HackBGRT (alot of code reused from it)
drivers/gpu/drm/radeon/radeon_bios.c