Doesn't it cut the speed of data transfer of each card in half when in sli? I believe that when you connect two pci express x16 cards it drops them down to 8x no matter what there are no motherboard / cpu that will run them both at x16. So you lose speed but I have no experience with this but im assuming your frame rates would drop in sli BUT you would be able to crank up the graphics to get double the graphics quality. From what I read that sums it up... Half the speed but twice the graphics quality.