So here's a quick update; I tried a few things to get it working; first tried holding ESC while the machine booted, held ESC all the way from power-on to the logon prompt, but got no dice. I also tried while holding down the blank key in the upper-left corner where ESC usually is. This did not work. I also took out of the loop a KVM switch I had been using (and still have to use for my tired old M5-II as the breakout block in the cable where it goes into two separate PS/2 plugs does not fit through the hole I bored in my desk for the keyboard and mouse cables... I should fix that the next time I have a big drill bit to hand). When it was connected directly to the only PS/2 port on the mainboard I got a message at boot-up about there being no keyboard detected. All the time the "power on" lamp on the keyboard was illuminated, so from this I guess we learn that it expects power on the same pin. Next step I think is hooking it up with a scancode viewer running to see if this thing even sends recognizable scancodes. Doubt I'll go further than that as, as I've said, the keys are mushy and I don't think it will be a particularly gratifying keyboard to type/game on.