Monochrome Display Adapter

And MDA card can be installed concurrently with a CGA card without interference. This possibility was intended by IBM for dual monitor applications. MS-DOS does not have any commands for dealing with this configuration but IBM-DOS allows for toggling off//on each monitor and setting the primary display using MODE commands.

Little known fact, the MDA can output red, green and blue TTL signals on 'unused' pins of the MDA connector and has a color/monochrome hardware setting. That would be, on or off for the three colors for a maximum of 8 colors and monochrome on/off to inform the monitor which mode is intended. Very few monitors are capable of interpreting this output correctly and no games that use MDA color are know to exist.