Color Generation in IBM CGA, EGA and VGA

(September 9, 2018)

It started quite innocently with a few Twitter threads about retro DOS gaming. The question was why no games (or any other software, for that matter) that were designed for EGA graphics cards made use of the additional colors EGA could offer. It’s widely known that EGA cards had a reprogrammable palette and could show any 16 out of 64 available colors on screen; but still, all software of the time just used the 16 default colors that were already possible with CGA graphics. Some explanations to this phenomenon were discussed, but it was mostly centered around what was possible and not why. Falling prey to nerd sniping, I dug deeper and deeper into the topic, including writing test programs in BASIC and Pascal, and now I finally understand everything about color generation in CGA, EGA and VGA cards.

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