I thought those things used a full sized DIN connector? Or do PC Engines use a different connector? Or require some sort of multiplexer for I/O?
I'm guessing the X-HE2 has also a custom IC inside. It wold be great if someone who has one will open it...
The TG-16 was the only one out of the bunch that used a full-size DIN connector, everything else uses mini-DIN.