That's on the video options page, right? Before you click on the "Advanced" icon? If so, I didn't mess with that. I went to "Advanced" and hit the "very high" settings button.
I have Far Cry running at the highest settings and I have no lag whatsoever.
I'm running an AMD 64 3400+ (2.4 Ghz), 2 x 512 Mb memory, and a Radeon 9600Pro.
I'm surprised it's lagging on yours.