A 256-Colour Adapter For The Ega

EE Mara- 1 88 A 256-COLOUR ADAPTER FOR THE EGA by Peter Balch . The IBM-PC enhanced graphics adapter (EGA) can display a maximum of 16 colours at a time. For many applications, such as the creation of realistically shaded three-dimensional images, this is simply not enough. The 256-colour board described in this article is offered as a design idea to ad- vanced users of the IBM-PC XT equipped with an EGA. The extension board plugs into the EGA feature con- nector. It produces analogue RGB signals, and TTL-level Hsync and Vsync. Many popular colour monitors accept either TTL signals from the EGA, or RGB signals from the 256-colour board, and can, therefore, be used both for the normal EGA modes and the new 256- colour modes. By default, the colour extension board is inactive, and the EGA works as normal: installing the board does not, therefore, affect the execution of existing pro- grams. EGA modes A complete description of all the display modes offered by the EGA is, unfortu- nat...