The 690's are two cards they run just like 2 cards.If sli isnt supported it will run like a stock 680.The main reason id rather have 2 680's instead of one 690 is mostly because you have a backup card if one dies and you are not put out of commision waiting for a refurb.I am also pretty sure that the 2 680's in sli will be alittle faster then the 690.Could be wrong though.