sli does not turn my computer on

darkshelby

Honorable
May 1, 2012
198
0
10,690
PSU:Cool master silent pro 1200w
CUP: I 7 3930k 3.20ghz
MOB: ASUS rampage 4 extrm
GPU: gtx 780 ti directcu II

So I install one gpu and everything works now I install the second gpu and sli it I put it next to my other gpu and now my computer wont power up. Board and gpu both has power. I remove the second gpu and put it on the third slot and still no luck. I remove the second gpu and now my computer turns back on again. What could it be.