A graphics processor may be operated in a reduced power mode to render frames at rate equal to or less than the rate at which frames are presented on an interconnected display. Graphics processor clock speeds are controlled to reduce the time during which the graphics processor is idle between rendering frames. The graphics processor clock speed may thus be slowed without impacting the quality of rendered images. At the same time the voltage applied to power the graphics processor may be reduced. Optionally, a back bias voltage may further be applied to the processor substrate to reduce power consumption. Clock speed and voltage levels may be adjusted using closed-loop control.