Originally Posted by Mrs Beanbag
...as if 1000 colours on CGA and tracker mods playing on internal beeper speaker is in IBM's tech docs anywhere
The composite signal is well documented as demonstrated by their research. All the hardware of that era was open since to take advantage of it you mostly had to use machine language. Today that isn't the case. You can only use OS dependant calls through closed source drivers and API to program gpus.
In the good old days you could feed your video card just about anything through a simple bios call.