I ordered the MPX-16 serial card board from Circuit Cellar because it was cheaper than the
IBM part at the time (it seems incredible that any computer intended for the home market
would have serial I/O as an option, doesn't it?).
I couldn't get it to work in a standard PC, so I figured that there was probably
something very different about the MPX's bus timing or signals and I lost interest in
the project.
Cheers,
Chuck