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
I can verify that both 5870s and 5970s work at x8 speeds, and assume they would work at lower speeds. I don't think there is any performance hit at all for mining, just for gaming which is more bandwidth intensive. I even think there is someone running 5970s out of modified x1 slots!
Wanted to let you know what the problem was. Turns out my motherboard, http://usa.asus.com/Product.aspx?P_ID=szSFtrap7crpBaQE, only supports either SLI or a single card. The second slot is not powerful enough to run a card on it's own. Go figure. Thanks to those who helped.
This is possible. The motherboard is responsible for 75W of a 5970's power (and probably something similar for 5870s)