A display controller includes first and second arbitrating units, a pixel data calculating unit, a latency measurement unit, and a clock divider. The first and second arbitrating units fetch first and second pixel data corresponding to at least one pixel from an external memory via a system bus. The pixel data calculating unit determines a size of the first and second pixel data. The latency measuring unit generates a first data rate value that is indicative of a latency of the system bus based on the size of the first and second pixel data. The clock divider receives a first clock signal modulation value corresponding to the first data rate value and alters a modulation of a reference clock signal. The graphics blending unit receives the first and second pixel data and provides blended pixel data to a display panel based on a modulated clock signal.