sli is achievable no matter what the manufacturer is as long its the same model. for ex a gtx frm gigabyte 680 can sli another 680 from msi or asus. however the only difference will come to play is for ex if one is at stock speeds while other is superclocked the superclocked will down throttle to match the stock. in short msi (980mhz) + asus(1020mhz) = together 2 cards running at 980 mhz. same goes with vram
Ok cheers, so basically whenever I decide to go for a shorter second 770 I have to make sure it's got 2GB of vram and a memory speed as close to the Gigabyte as possible, to get the most out of the combination.