Mike wrote...
what the difference was between a 2100a and a
2100s. Now, I have
There really isn't any difference, sort of.
The 2100S came with a set of options that the 2100A didn't come with by
default but which could be ordered with the 2100A. I forget which options,
perhaps hardware FP.
Surely the 2100S has user-writeable microcode? The front panel
says "Microprogrammable Systems Computer":