I have had 2 evga 780 classifieds running in sli with no issues up until about a month ago when all of a sudden my frame rates plummeted from averaging 100+ in bf4 on highest settings to just over 60 so I ran some benches and saw the same thing happening I have built a few computers that part comes easy to me its the diag that im lacking in experience in but the things ive done thus far are check my setting and in the settings it says sli disabled and no where is there an option to turn it back on both cards have power and all the lights are on and fans are running ive tried different bridges and there was a driver update and with new drivers still no sli....im thinking mobo maybe i should have supported the weight of the cards better im not sure my mobo is a asus crosshair v formula z and i have an xfx 1000 watt psu only other issues i have been haveing with my system are that my r key will occasionally double input and i had one boot hang