25 Dec
2010
25 Dec
'10
10:13 p.m.
FWIW...
From: allison <ajp166 at verizon.net>
Minimal system:
8080, 8085, NsC800, Z80, or Z180 cpu. The prefered CPU is z80 as
it's easy to interface and there are some CP/M apps that require it.
64K ram, (technically cp/m runs in 20k or more but useful apps are
minimally 48K)
Boot rom(eprom/flash) that maps out of the 0000h startup address
Mass storage, this can be floppy, CF, SD, Or some form of rom/ram to
look like disk.
User IO, typically a serial line for a terminal can be a memory mapped video
and keyboard or similar.
For my high school senior project, I designed and built essentially this,
significantly over 20 years ago. Z80, 64k RAM (4 x 16Kx8), serial port, simple relocating
boot ROM, relevant CBIOS, floppy. I had a TRS-80 4P running Montezuma CP/M (thanks, Dad)
to write code on and a random EPROM writer to program 2764s. Got it to boot CP/M in a
semester, working an hour or more daily, 5 days a week. I'd also generally figured out
how to interface, for local reasons, to STD-Bus for expansion, but never actually
implimented it. Had an Intel bubble memory dev kit (128k), but also never got around to
it.
Went to college, had Vaxen, 3B2s and early Suns with Unix and C, with a sprinkle of
Pascal, Modula-2 & Ada followed by Symbolics and Xerox AI machines. And I relized how
much more interested I was in solving big problems than figuring out what problems I could
fit into tiny computers, and never looked back. Maybe I'll see if I can find the
remaining bits and notes in the basement one day.
Point being, it's an imminently doable project, of variable utility these days, and
there's a ton of existing work that can be leveraged.
KJ