I have an ASUS P8Z68-V PRO motherboard, so it's not really the same, obviously. However there's a section in my manual with a chart that tells me exactly how to place the cards in both a single and dual card configuration. There's also a note that says "In single VGA card mode, use the PCIe 2.0 x16_slot (navy blue) for a PCI Express x16 graphics card to get better performance." Even though two of my slots are x16 ASUS still recommends that I use the top one when I'm just using one card. If you can't find anything like that in the manual then you should call or email ASUS. I've used their phone support several times and they've all been good experiences.