Method of providing a second clock while changing a first supplied clock frequency then supplying the changed first clock

Abstract

Methods, circuits, and apparatus for changing a frequency of a clock signal provided to a graphics memory while reducing any resulting visual glitch or disturbance on a monitor. A specific embodiment provides multiple clock sources that may be multiplexed or selected to provide a memory clock signal to the graphics memory. The multiplexer switches from providing a first clock source signal as the memory clock signal to providing a second clock source signal as the memory clock signal. The first clock source changes its frequency of operation. After the first clock source settles or stabilizes, the multiplexer switches back to providing the first clock source signal as the memory clock signal.