Cute, I made that guy an offer on it because I'm writing a game engine in TP7 that I want to make sure is fast enough for a 4.77mhz 8088, he accepted... I google for more info on the HX, and I find a thread about the unit I won!
That custom card peaked my interest too, so I'll report what it is as soon as I have it in hand. As it looks like a five pin I can think of a few possibilities:
1) Keyboard adapter. Entirely possible since there is no external keyboard jack, maybe the internal keyboard is bamjacked?
2) Cassette port. Some early PC software did come on cassette, or perhaps it's to transfer data off old TRS-80 tapes?
3) Midi. "Dumb UART" midi is just 31250 baud serial that can be implemented with a handful of chips. I think that is the most likely candidate.
I'm going to start digging through my old 80 micro's (I have most of 1982 through 1988) to see if there's anything similar in there for projects. The '87 and '88 issues were mostly about the 1K anyhow. Could even be a "commercial" product as a lot of the stuff advertised in '80 Micro were often slapped together on perf board in someones basement.
IF it works this will make a excellent testbed for the range of capabilities I want my 'retro game' engine to be able to target... I'm aiming for 160x100x16 cga (that also works tandy/ega/vga in that mode, which I figured out how to do by forcing REAL mode 3), 320x200x16 ega/tandy/pcJr and 640x480 VGA all from one game engine (with ease of porting to SDL/Free Pascal) -- much like how the old Sierra games were adaptable on the fly.
Quite a retrocomputing month for me -- I got a stack of
Coco's last month, been programming 6809 ASM for coco and 8088 under DosBox, now I've got a HX on the way.
I'll check back in to report on that board tomorrow after I get it.