adaptive vsync
 

вот такая есть интересная штука:

Adaptive Vsync
Recent GL drivers implement a new WGL/GLX extension called EXT_swap_control_tear. This extension brings "adaptive vsync" as featured in modern gaming consoles to the PC.
Adaptive vsync enables v-blank synchronisation when the frame rate is higher than the sync rate, but disables synchronisation when the frame rate drops below the sync rate. Disabling the synchronisation on low frame rates prevents the common problem where the frame rate syncs to a integer fraction of the screen's refresh rate in a complex scene.
Adaptive vsync can be enabled with wglSwapIntervalEXT(-1) or glXSwapIntervalEXT(-1).

Ответ: adaptive vsync