I found myself a second-hand GTX 980 to replace my ageing GTX 590, but when I installed it I couldn't get past the BIOS splash screen. Thankfully I have a dual BIOS motherboard (Asus Maximus IV Extreme-Z) so I was able to copy the default BIOS from the other chip which let me boot. It seems the problem was the PCI ROM priority was set to "EFI Compatible ROM" instead of "Legacy ROM".
What is the problem with "EFI Compatible ROM"? Is there anything wrong with my graphics card? Is there anything I can do to make it work?