A display control apparatus comprising at least one display controller arranged to transmit composite pixel data to at least one display device at a rate defined by a pixel clock signal. The display control apparatus further comprises at least one pixel clock control component arranged to receive an indication of a number of graphics layers to be blended for the composite pixel data to be output, and to configure the pixel clock for the transmission of the composite pixel data to the at least one display device based at least partly on the received indication of the number of graphics layers to be blended.