OT: how big would it be?

From: Mike Cheponis <mac_at_Wireless.Com>
Date: Wed Oct 20 10:27:33 1999

> > Say someone were to home-build a CPU from scratch using only individual
> > components, no ICs only modern discrete(?) components. How big would the
> > CPU be? For comparison lets say it would be an 8080 clone. Any guesses?

It seems to me the Right Answer is to approximate the number of transistors
required. How many transistors did an 8080 have? (Do remember, however,
that the transistor count is actually less than you'd need with discrete
transistors, because the on-chip transistors can have multpile emitters or
gates or whatever in the same device.)

As for how "big" it would be (that is, its size), modern discrete transistors
are available in tiny SOT-23 or even tinier packages. Resistors are
available in 0402 and maybe smaller. Line widths on PC boards can perhaps
be as small as .002 inches, and they can be many layers, a dozen or more.

So, in order to compute the size, I think you'd need to make two estimates:

1) The number of transistors per cubic inch (or cm if you like those units)

2) The number of transistors required.

This assumes some packaging/connector allowance is taken into account to
estimate the number of transistors per cubic whatever.

------

IMHO, if you're going to build something from transistors, why not build
something that was originally built with transistors? For example, the
IBM 1620, 1130, 1401, etc. Or if you really want to get funky, try something
like transistorizing a tube machine, like ENIAC or JOHNNIAC or Bendix G-15.
-That- could be entertaining...

-Mike Cheponis
Received on Wed Oct 20 1999 - 10:27:33 BST