A graphics display system for a computer comprising a display memory having a DRAM port and a serial port, a video controller including a host graphics controller having a bus port, a lookup table and a digital-to-analog converter for receiving lookup table data from the lookup table and converting it into signals reproducible by a display, the DRAM and serial ports being multiplexed to a combined bus, the combined bus being connected to the bus port of the graphics controller, the lookup table having an input for receiving data from the combined bus, apparatus; fur causing passage of serial data along the bus from the display memory in higher priority than any other data for provision of display data to the lookup table whereby the lookup table can provide the lookup table data to the digital-to-analog converter.