I've got a Peritek VCU-V/16 board with a TMS34020 (similar to this board
Unfortunately, it didn't come with firmware EPROMS. Probably robbed by the surplus parts goblins back when I bought it.
Anyway, I've got it loading custom firmware using the toolchain from bitsavers plus a bit of custom ROM-generating code to massage the output of the GSP tools in just the right way. I can single-step through my code up until it accesses the serial port, which is waiting for terminal input. I may put the project on github if anyone is interested.
I did have a question for the MAME experts here apropos terminals on graphics boards. How do I connect to the rs232 port I defined for the SCN2681? Searching shows there's a '-rs232' command, but the current build (or mine) doesn't acknowledge that flag at all. I've scoured the googles and it appears you must build the console into your app, which I did. But that seems to conflict with also having a graphics display. I haven't found an example (yet) that has both a terminal port and graphics. MAME gets confused with having two displays. Yeah, I'm probably doing it wrong.
I was hoping for a way to telnet to the device or somehow use minicom through a virtual terminal device.)
I also have an MVME-167 board. It would be interesting to get some kind of unix running on it with X using this graphics board.