I've seen somone use the benchmark command with a loop, that if the benchmark was lower than 5000, it would loop every ~0.4 seconds, and higher, it looped ~0.2 seconds.
So I think 5000 should be right altough that person could have had a bad computer. Im not sure. You should try it out.
My computer wont have any propblems with ofp other than the very high terrain settings.. strange! I expect my benchmark to be greater in OFP with my:
radeon 9800SE
amd athlon 64 2800+
and so on with the flashy stuff ;D!