i have 2 of the same boards running win 8.1 and 6 cards in each. I had to short the 2nd and 3rd PCI x16 slots. Also, in the BIOS I set the PCI slots to GEN 1
What OS are you running? I could not get XUbuntu/Ubuntu to boot up consistently, so that is why I am using win 8.1
Also, the motherboard manual will tell you what the bios error means - at work right now so can't look it up.
how can you short x16 slots? is there any diagram