My lightning 780 would do 1350 on the core on air like 6+ month back. 347+(cant remember where it started) drivers not so much got stuck with around 1250. If i revert to earlyer drivers i got my OC back.. Then there's topic around the net that Kepler got a volt nerf through drivers.. never got around to test that to see if it was true. Wouldn't surprise me considering my old 780 would give a 980 g1 gaming running stock a run for its money in firestrike with just 1250 on the core getting just a hair under 12k in gpu score which is matching the 980 according to guru3d.