Any *really* homebrewing going on?

From: CLASSICCMP_at_timaxp.trailing-edge.com <(CLASSICCMP_at_timaxp.trailing-edge.com)>
Date: Sat Oct 3 15:51:05 1998

>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_at_trailing-edge.com
 Trailing Edge Technology          Voice: 301-767-5917
 7328 Bradley Blvd                 Fax:   301-767-5927
 Bethesda, MD, USA 20817
Received on Sat Oct 03 1998 - 15:51:05 BST

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