[phil@f15 ~]$ vblank_mode=0 glxgears ATTENTION: default value of option vblank_mode overridden by environment. ATTENTION: default value of option vblank_mode overridden by environment. 314 frames in 5.0 seconds = 62.729 FPS 386 frames in 5.0 seconds = 77.187 FPS 396 frames in 5.0 seconds = 79.022 FPS 449 frames in 5.0 seconds = 89.776 FPS 393 frames in 5.0 seconds = 78.580 FPS XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":0" after 2312 requests (2312 known processed) with 0 events remaining. [phil@f15 ~]$ glxgears Running synchronized to the vertical refresh. The framerate should be approximately the same as the monitor refresh rate. XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":0" after 34 requests (34 known processed) with 0 events remaining.