Quote Originally Posted by Gautam View Post
It's because you're running with HT off.
Ummm, maybe donmarkoni would be kind enough to do 3 runs @ 4GHz of 64-bit with say 4GB of mem (24000). I would expect ~90% of full SSE with no HT (6 threads) and ~75% of full SSE with HT (12 threads).

HT = ~72GFlops
No HT = ~86GFlops

FWIW even though using SMT (HT) gives lower Flops it uses more power, ~10% more on my 860, so is probably more stressful than the higher Flops on separate physical cores.