more chording keyboards

I guess you're talking about the ADB keyboards which work with the Macintosh. (The same keyboards work with the Apple //gs, so I guess this message IS on topic after all!) There's only one specification I've seen for them: You can press as many modifier keys as you want at the same time, but only two letter/number/ punctuation keys. I think that means they have two-key rollover. The power key is handled differently from the other keys. I wrote a program to show key-down and key-up events, to test my keyboard (in case I could somehow "cheat" and get more-than-two-key rollover) and found I couldn't cheat, and the spec was correct. I forget if I had bought my non-Apple keyboard by then. So most of the special combinations involve modifier keys. Command-control- power is reboot (same as Ctrl-Open Apple-Reset on the //gs) and the trickier combinations include letter keys as well. The "Zap the PRAM" sequence is Command-Option-P-R. There are a number of combinations like that, and they all have two letter keys. I've always wondered how you make a keyboard that has two-key rollover, or N-key rollover for that matter. I know that most keyboards these days scan a matrix of switches, but I don't know where rollover comes into that process. -- Derek