To give us flexibility, we are working with the Dallas 89C420 at 11Mhz which, after driving video, still leaves us with enough free instruction cycles to execute code approximately 16 times faster than a traditional 12-clocker.



We considered that--especially for the video. But currently it looks like all the major features of a simple computer can be handled by a single '420. So as long as it can do it, we plan on doing it with a single-MCU approach.



I suspect we probably will eventually. I was originally thinking of making it an adapter board for the SBC but I don't think that'll be useful since the '52 computer will have some very specific input/output (PS/2 keyboard/mouse and video output and an SD card slot, or maybe CompactFlash, who knows) which makes things like the 4x4 keypad and 16x2 LCD circuitry entirely useless to the computer. So it'll probably end up being a brand new PCB.

We're still a long ways off on that, though. First we need to get all the parts working to our satisfaction, then we open it up as a public project where everyone that is interested can argue about the best way to connect the parts, the memory map, etc. THEN we'll be ready to put together a PCB. :)

Regards,
Craig Steiner