So I changed the PCI ROM Priority setting from the default UEFI to Legacy and it hasn't fixed the issue. I've checked this issue on other forums and it looks like that was the only cause. I find it strange that the newer GPUs would be incompatible with the UEFI boot rom whereas my HD 5570 works fine with it. I wonder if having an engineering sample Xeon E5-2650 has anything to do with this.
4/19/14 at 4:41pm