TechReport reports that the revised 8800 GTS 640MB cards are, in fact, based on the G80 GPU, and they simply have an additional SP cluster enabled internally, giving them 112 SPs and a little more texturing capacity. Because they're based on the G80, these cards do not have the VP2 decoding engine, doubled texture addressing capability, or power consumption improvements found in the G92 and the GeForce 8800 GT.