Heh, I tried maxing out LFS (all in-game settings maxed, 2048x1536 with 6xAA + temporal AA + adaptive AA + 16x HQ AF), and I get ~70fps on my own on some parts of the track, but as low as 17fps in some places. Dunno why that is really, everything looks about the same, I'm assuming my minimum FPS is CPU limited.
Even reducing the resolution down to 1600x1200 doesn't get my FPS that high, peaks at 85fps, yet down to just under 30fps in some sections. So I dunno how the hell you can sit there at 100fps.
I'm running Athlon 64 3200 (2.02GHz) + Radeon X1800XT (256MB version) + 1GB 667MHz DDR2.