Minimal CP/M SBC design?

[Tim Shoppa]

Ethan asks:
> I am a little unclear, though, about how traditional CP/M systems
> were set up for ROM and RAM.  Was it common to use a "shadow ROM"
> in low mem at reset, then have the BIOS live at the top of memory?
> How did 64K RAM CP/M machines handle the BIOS?

The most traditional CP/M system has a toggle-in front panel and
16K of RAM, Ethan :-).

The much later CP/M systems that had boot ROM's either had them
consuming a small amount of high memory permanently with some
hardware hackery to jump there on a cold reset, or lived in
low mem at reset and had a later stage of the boot process map
them out.

And I am perplexed by your BIOS question. I think you are using
that acronym in a non-CP/M context. If you want to read the
"CP/M 2.0 System Alteration Guide" and rephrase your question I
think we could make some progress.

Tim.