Hrm, I currently have a 5830 in my x1 slot using a x1 to x16 riser cable, which the system sees and it mines well. Although, the x1 acts in some ways like it's the primary slot, that's where the POST display is shown. I suspect this causes some of my stability issues I am seeing. I suspect it's because the x1 slot is closer to the CPU, it is actually first on the bus.