I have tried slot 1 and 2 then my one card (Slot 1) runs at 8, and the other (Slot 2) at 16 accordint to GPU-Z
Slot 1 and 3 both run at 8
Slot 1 and 4, 1 card(Slot 1) runs at 8 the other (Slot 4) at 16
Slot 2 and slot 4 run at 16, but don't really want my cards so close together due to heat.
Did a test last night and with the 2 cards in slot 2 and 4 my top card was almost 20 degrees hotter than the bottom one switched them around and results were the same (max on top card was around 76 both times)
Im using 2x EVGA GTX 460 SC EE, and a Corsair HX 850w also have the latest bios update from Asus.
Could it perhaps be a setting in the Bios? Or the fact that I don't use the molex connector on the MB for more power to the PCI-E?