Abstract: An interface for adapting an Apple.TM. II series computer, having only a video output suitable for driving an NTSC-type monitor to drive an RGB-type monitor. In the preferred embodiment, the interface subdivides the computer's double-density high resolution (HIRES) video mode output having 560 transitions/monitor scan line into any of four (4) video modes for display on the RGB monitor. The interface can be provided on a card incorporated into the computer or as a unit separate and distinct from the computer and connected therewith via a cable.