From memory, the CoCo uses a 70ns (or 14.28MHz) pixel clock when using a 640x200 resolution. As far as memory bandwidth is concerned. The GIME needs to read from memory once for every 8 pixels (2 bits per pixel, 16 bits per read) which works out to one read for every cycle at 1.78 MHz. -- Theodore (Alex) Evans | 2B v ~2B = ?