GTX 280 is about 933 GFLOPS performance, but the double-precision performance is only about 90GFLOPS, about 1/10 of peak. they are not my number, mostly from http://www.heise.de/newsticker/meldung/109495 . I got about 40GFLOPs on double-precision.
anybody know the hardware reason behind? how about the coming telsa s1070 for the dp support?