glenn9k@bumblebeebox:~$ glxgears
Running synchronized to the vertical refresh.  The framerate should be
approximately the same as the monitor refresh rate.
303 frames in 5.0 seconds = 60.588 FPS
300 frames in 5.0 seconds = 59.824 FPS
300 frames in 5.0 seconds = 59.830 FPS
300 frames in 5.0 seconds = 59.826 FPS
^C
glenn9k@bumblebeebox:~$ optirun glxgears
5002 frames in 5.0 seconds = 1000.312 FPS
5047 frames in 5.0 seconds = 1009.346 FPS
5057 frames in 5.0 seconds = 1011.194 FPS
5045 frames in 5.0 seconds = 1008.916 FPS
^C[85536.901748] [WARN]Received Interrupt signal.