Ty for the quick reply, Andrew!
ok, here's the output for glxgears:

wjf@linux:~> glxgears
20042 frames in 5.0 seconds = 4008.400 FPS
20548 frames in 5.0 seconds = 4109.600 FPS
20548 frames in 5.0 seconds = 4109.600 FPS
20550 frames in 5.0 seconds = 4110.000 FPS
20548 frames in 5.0 seconds = 4109.600 FPS
20549 frames in 5.0 seconds = 4109.800 FPS
20551 frames in 5.0 seconds = 4110.200 FPS
20550 frames in 5.0 seconds = 4110.000 FPS