Originally Posted by sneekypeet
card may be throttling or going into power saving mode. Run GPU-z to log the information from the sensors next time you play and see if there is anything odd there. Look for spikes in temperature or some other anomaly at the time the card looses FPS.
thats what im thinking too overheat and then drop to 2D clocks my 260 does it when i push past 95C damn card.