Reverse Engineering the Video Chip of the IBM CGA Card (1981)

We try to non-destructively figure out the HD6845 chip used on some IBM CGA cards from 1981.

Lots of new glitches are found along the way, and we freeze snow in place for possibly the first time!

Many thanks to Sean Riddle who let me use his die shot of this chip:

http://www.seanriddle.com/6845/

Viler's Font website:

https://int10h.org/oldschool-pc-fonts/fontlist/font?ibm_cga

Reenigne's blog:

https://www.reenigne.org/blog/adventures-in-crtc-lockstep/

Here is a link to a document (heavily under construction) in which I describe the result of some of the experiments I've done so far. Bear in mind this document has a long way to go until completion.

https://github.com/wbhart/crtc/blob/master/crtc.pdf

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