Area 5150 is a demo. More about it: https://www.vogons.org/viewtopic.php?t=89435

(For those unfamiliar with “demo” in this context, see https://en.m.wikipedia.org/wiki/Demoscene)

Interesting submission from about a week ago:

"A cycle-accurate IBM PC emulator in your web browser" https://news.ycombinator.com/item?id=43888007

It runs Area 5150 upon launch, so that's a good way to see the demo if you don't have an IBM 5150 handy.

It's not every day that an emulator author has to resort to analyzing bus-sniffer traces to debug and fix a demo effect - and certainly writeups that go into this level of detail are few and far between!