https://bugzilla.kernel.org/show_bug.cgi?id=66791
--- Comment #6 from moonman moonman.ca@gmail.com --- Just a quick update: I managed to get it to work finally, though this is not really an optimal solution.
1. Patched the kernel with this patch: https://bugs.freedesktop.org/attachment.cgi?id=33766 from this bugreport: https://bugs.freedesktop.org/show_bug.cgi?id=26891
2. Extracted the vbios while booted into archlinux live cd in bios mode (by the way the live cd needs to be patched to be booted because it comes with EFI 64bit support and not 32bit - well described how to do it in ArchWiki)
3. Only 1 method worked to extract the bios:
echo 1 > /sys/devices/pci0000:00/<id>/rom cat /sys/devices/pci0000:00/<id>/rom > vbios.dump
for me id=0000:00:02.0
The resulted image is 64000 bytes and does not work for loadbios in grub. Really don't know why.
Actually there's another method: If you have windows installed you can use aida64 to extract the vbios. GPUZ does not work.
Now I can succesfully boot into KDE, BUT only if booted using grub. With EFI Stub I get to console (screen does not stay black anymore), but X server fails to start.