The problem probably has to do with the difference between a PCIe x16 and a PCIe x8. Both of our MBs have a single x16 and a single x8 slot. Apparently ATI 58xx and higher cards require x16. Without this no card in the system work. So, because you have a 5970 in the second, PCIe x8, slot your system will not function.
Very disappointing.
Very disappointing.
Any source for that information? Or is it just based on your observations? I'm fairly sure they work on x8 or even x4...just with a performance hit.
Check this benchmark out:
http://www.tomshardware.com/reviews/p55-pci-express-scaling,2517-3.html