Tech question

[Grumbler]

A Long time ago some of the early Cad-Cam systems did that. They used non standard code to control the raster scan and freq. They did that because at the time there were no standards for Large (>17" CRT's). There was a flashable EPROM that sat between the input and the E-beam controller. You could tell a monitor was set-up that way by looking at the input cable. If it wasn't a standard CR232 19 pin connector ( I think, it's been a while) but 3 jacks like you see on a VCR, then it was a non-standard Monitor. They were used also for AV feeds. I played SP1 on a 30 incher back in 97 or so.
Radio Shack used to sell conversion plugs for them. Obviously, I'm bored and need more turns.