Now I was young and dumb at the time, and I had decided for some reason to jokingly call the simple bit bashing communication protocol I'd invented to talk to my chess computer "V.69" (The V series protocols - eg V.24 = RS-232 in the USA were big at the time). A V.69 port had actually made it into the final schematics for our board. It was just 5 logic level pins (two inputs two outputs plus ground) - and in production it would not have any impact - but it was possible to solder a 5 pin header onto the pins, and hook it up to a PC running the same terminal software previously discussed - If such a PC was connected my embedded code would emit diagnostic information.
We had many meetings during our visit, with the typically gruff non-nonsense Dutch engineers and their huge vats of extraordinarily strong coffee. One of them was with "the Standards guy" who wanted to audit compliance to all possible standards - I was able to spectate mainly as it was hardware stuff. But suddenly he was pointing at the V.69 connector, clearly labelled as such. We'd forgotten all about it. Us> "Oh well, arrrgh, yes. It's a diagnostic port - for the lab only - no impact on production - the header is just omitted." Him> "But what is this V.69 standard?". Us (hopefully)> "Well, it's just a 5v serial diagnostics standard". Him> "Okay, yes I've heard of it". So as is often the case, the need to save face saved the day.
The scary part is that most departments in Philips still prefer heavy processes over progress. I, for one, didn't last more than 6 weeks there.
I miss those days as well. It's a lot easier to repurpose things made out of through-hole mounted 7400 series logic than all the custom surface mounted stuff you see today.
On the flip side, though, back then to make your own boards you had to shell out thousands of dollars for the software and more thousands for a prototype run.
It does make me wonder what made you go all of this instead of doing that? It obviously wasn't just your need to program on an M68k. I think you are more of a hardware genius than you want to let on. Either that or you are just good at everything.
Like you, I cut my teeth in the 80's .. never trust a coder with a screwdriver, amiright .. but it seems that a rejuvenation of this ethos is upon us, with the Arduino and Maker crowd producing plenty of young developers who know how to burn their fingers ..
Then I worked out a simple serial bit twiddling scheme to exchange bytes a bit at a time and coded it up in C as a kind of software serial port. On the PC side I ended up with something that looked just like a simple terminal that happened to talk out the printer port. On the Mephisto side, I replaced the 64K byte EPROM with a 128K byte EPROM. I changed the cold boot vector to point at "my" 64K, which first checked to see if the printer port was hooked up. If it was hooked up, then the CPU stayed in "my" area and ran a monitor I had coded up for the occasion. If it wasn't hooked up it vectored back to the original boot code and the chess computer worked as well as it ever did. I layered a loader on top of everything and enjoyed loading simple cross compiled C programs on my new 68K computer, (complete with 16K RAM).