 So the HEMA graphics was turned into an external "graphic box" and connected with the IBM AT via the parallel port.A next major improvement was the introduction of an expansion board using the Hitachi ACRT graphics controller HD63484.With up to 1 megabyte of video RAM, it was possible to create a 1600×1200-pixel graphic with four bits/pixel and display it on a 1024×786 cathode ray tube (CRT) display.