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Re: S-100 Motherboard

Andrew  & the group:

Some more testing today yielded some progress. I have now installed my
floppy controller and the hard disk interface board on the
motherboard. Neither is connected to drives.

Good news is that the system still resets on power up and the basic
monitor functions work.

Next step will be to try booting CP/M after connecting the drives -
very big step.

I did run into a couple of issues today:

a. First, the pin numbering on P2, P3, P4, & P5 on the motherboard is
wrong as long as you think the square lands are pin 1 for each of
these headers. If you assume the square lands are pin 2 then all is

b. At first I could not get an external /PRESET to work. To make a
long story short - the circuit was fine - I had a switch set wrong on
the CPU-Z. The fascinating thing is that I don't think I changed it on
purpose so that may explain some problems with my old system. It is
working fine and testing also reveled that all I really need is a
switch that will ground bus pin 75 to do a reset. No active circuitry
is needed.

Next steps are the toughest ones though.