Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!cica!iuvax!jwmills
From: jwmills@iuvax.cs.indiana.edu (Jonathan Mills)
Newsgroups: comp.theory.cell-automata
Subject: VLSI CAs (was Re: hiebeler's rap)
Message-ID: <37683@iuvax.cs.indiana.edu>
Date: 2 Mar 90 13:15:42 GMT
References: <9003020522.AA25938@megalon.acad.com>
Reply-To: jwmills@iuvax.cs.indiana.edu (Jonathan Mills)
Distribution: inet
Organization: Indiana University, Bloomington
Lines: 34

In article <9003020522.AA25938@megalon.acad.com> Rudy Rucker writes:
>
>Using a lot of states to represent all components is a nice idea.  You
>can have states 0 thru 255, so you can have a cell that is aan and gate,
>a cell that is an or gate, a cell that is a source of faults, etc.
>So then you can make tiny tiny wireworld circuits.  And animate them.
>Chip designers use something like this, I guess, tho they run slowly?

I've investigated cellular automata for VLSI simulation and verification,
and am still working with it.  But no tools, either mine or others I am
aware of (various signal-level circuit simulators, digital simulators,
or symbolic simulators) use the wireworld approach of "duelling electrons."

It's cute, but it is too far divorced from the properties of the circuits
to be useful (IMHO; no insults to clever originators of concept or the
wireworld program; flames to /dev/null).

Circuit simulators commonly used solve for increasingly complex sets of
partial differental equations (from what I've seen of Spice documentation),
and attempt to find the fixpoint of that set of equations (i.e., "converge").
Sometimes they don't.

The VLSI CAs I've worked with model various transistors, gates, oscillators,
and networks, and can be compiled from MAGIC layouts -- although I haven't
automated the process.  Their behavior is similar -- but not identical --
to the "real" thing, in part because the model embedded is _much_ less
complex.

Certainly the VLSI CAs _do_ run slowly;  they are not realistic for circuits
of interest.  Consider that university tools (Spice, again) may run for days
to compute the behavior of a complex circuit.

Sincerely,
Jonathan