Emulators of Classic Computers

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Mon Jan 19 14:30:12 2004

>> [...learning electronics...]
> Tssss. Not to discourage you, but a TTL computer with bazillions of
> ICs is not really suited for newbies, although there is plenty to
> learn - namely on those nasty aspects like circuit timing, delays,
> glitches, noise on power and signal lines. TTL is to a large degree
> analog, not digital, circuit development ;-)

Once, years ago, I was involved in building a designed-on-the-spot Qbus
board. We actually managed to convince ourselves we had a bad 74123
for a while - until the replacement misbehaved exactly the same way.
(There must have been coupling issues somewhere; adding caps on the
power rails made the problem go away.)

> You might not directly want to start with a monster like Computer 74
> or EGO, but perhaps with a simple ALU/register device: get a 2901
> circuit from BG-Micro and play a bit with it (a breadboard with lots
> of switches and LEDs is sufficient). And then extend it with a
> 2909/-10/-11 from the same source and build the micro control for
> that toy.

Good advice. Start simple. My first major piece of TTL hackery was a
little toy 4-bit microprocessor; the most complicated single chip used
was a 4-bit ALU whose 74xxx number I forget by now. (Oh, and a chip
which was basically a 16-word static RAM with 4-bit words.) I was
fortunate enough to have a _really_ _nice_ breadboard to work with.
None of this wish-board stuff; it had individual IC sockets with very
nice machined contacts, and the wires had little stackable plugs (a bit
like banana plugs done tiny) on the ends of them. All contacts were
gold-plated. I shudder to think what they cost the University, but
they were _so_ pleasant to use.

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Received on Mon Jan 19 2004 - 14:30:12 GMT

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