[endtime]

Right, yes, but the (semi-serious) point is that we don't have a crab grid in the same way we have a power grid, so actually implementing this (which is what the article is about, rather than just theory) might be hard. For the crab computer to "run" arbitrary computations it would need an arbitrarily large source of crabs.

[jws]

A functional crab computer would probably have to be built from delay insensitive logic[1]. The outputs of the gates would be of the form X and !X, where the signal (crab cluster) would appear at the appropriate output.

With regards to crab supply, I think the sufficient study of reversible computing, and in particular their charge conservation properties, would address that.

You'll still have to have a mechanism to spray bits of dead fish around to feed the thing.

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[1] http://en.wikipedia.org/wiki/Delay_insensitive_circuit

[2] http://en.wikipedia.org/wiki/Reversible_computing