OT: how big would it be?

From: Richard Erlacher <edick_at_idcomm.com>
Date: Wed Oct 20 11:05:09 1999

Well . . . if you mean really discrete, i.e. no TTL SSI/MSI stuff, you need
to recall that a single flip-flop was resistors, capacitors and a handful of
transistors. Really cramming the parts together still meant a flipflop took
up space equivalent to, say, a postage stamp. I've seen claims that some
old-style CPU's (e.g. 8080) could be built in programmable logic using fewer
than 500 macrocells in a large CPLD. Now, that's a BUNCH of logic gates,
maybe four transistors and some resistors, and 500 of these postage-stamp
sized flipflops.

There, methinks you'd be talking about a board as big as your dining room
table, with miles of wire, and potentially millions of errors to correct.

Dick

-----Original Message-----
From: CLASSICCMP_at_trailing-edge.com <CLASSICCMP_at_trailing-edge.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Wednesday, October 20, 1999 8:24 AM
Subject: RE: OT: how big would it be?


>>I know its off-topic but i figured that since most of the poeple on this
>>list work or have worked on the really big stuff you'd know better than
>>most others.
>>
>>Say someone were to home-build a CPU from scratch using only individual
>>components, no ICs only modern descrete(?) components. How big would the
>>CPU be? For comparison lets say it would be an 8080 clone. Any guesses?
>
>Well, others have guessed at the 8080 Clone, but I'll step in and point
>out that if minimal part count is an important feature, then you can
>get by with a *lot* less. Especially if you go to a bit-serial
>architecture. (Something that's still mentioned in many computer
>architecture textbooks, even if it isn't used much anymore!)
>
>How big? I'll venture a guess that a 12-bit serial CPU
>could be done on one largish (i.e. a square foot) PC board, using
>TO-92's, resistors, capacitors, and diodes. This isn't too far
>out of line with many bit-serial designs from the late 1960's
>(for example, many bit-serial desktop calculators used a PC board
>- or two or three - about this size.)
>
>Total cost? Maybe $1500 in large scale production, including testing
>costs.
>
>Of course, you now hook up memory to this CPU. Doing that with
>discretes would be a chore!
>
>--
> Tim Shoppa Email: shoppa_at_trailing-edge.com
> Trailing Edge Technology WWW: http://www.trailing-edge.com/
> 7328 Bradley Blvd Voice: 301-767-5917
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Received on Wed Oct 20 1999 - 11:05:09 BST

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