3 Oct
1998
3 Oct
'98
8:51 a.m.
hard to come by these days, but how about modern
equivalents? I think
that's the lowest level I'll personally go, although it would be really
fun to build a 4-bit computer out of transistors, anything more complex
is probably really difficult.
Why not go for a bit-serial (aka 1-bit) CPU? It's an extremely classic
design, and is certainly the way to go to minimize total transistor
count.
I've got some plans of designing a computer this
year. I'll probably
get my feet wet with a simple 4-bit design, but I'd like to do a 12-bit
computer (since my "inspiration" is a PDP-8).
The PDP-8/S is a -8 done in a bit-serial implementation. 78 microseconds
for some instructions!
If you don't mind making about a 15-year advance in the electronics
you'll be using, you might also seriously consider making a CPU via the
state machine route, using an EPROM and some counters. All math and logic
operations can very easily be done via table look-up in the EPROM. This
is a rather common assignment in lower-level computer engineering courses,
as it's something that can be easily wire-wrapped in an afternoon or two,
and it is extremely easy to try new microcode revisions.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology Voice: 301-767-5917
7328 Bradley Blvd Fax: 301-767-5927
Bethesda, MD, USA 20817