Power usage?

Posted Jun 19, 2008 8:37 UTC (Thu) by epa (subscriber, #39769)
Parent article: The Kernel Hacker's Bookshelf: Ultimate Physical Limits of Computation

As you mentioned, these numbers don't take any account of power usage or heat dissipation.  It
would be interesting to know the theoretical limits of a one kilogram, one litre computer
drawing one watt of power.

Power usage?

Posted Jun 19, 2008 12:02 UTC (Thu) by emk (subscriber, #1128) [Link] (2 responses)

Basically, if you're worried about power and heat, you want to know the fundamental limits of reversible computation. A reversible computation is, of course, a reversible machine, and therefore uses no energy (except for output bits). Richard Feynman actually wrote a nice essay on this problem. And as it turns out, you can still do an insane amount of computation per unit time, under the laws of physics.

Of course, it's probably impossible to actually construct a true reversible machine, although certain small-scale quantum phenomenon, such as superconductivity, come surprisingly close.

Power usage?

Posted Jun 20, 2008 8:39 UTC (Fri) by epa (subscriber, #39769) [Link] (1 responses)

I was just thinking of normal, non-reversible computation, constrained to dissipate at most
one watt of heat.

Do any reversible computing devices currently exist?  (Yes, I know a NOT gate exists, but I
mean something computationally more powerful than that, preferably Turing-machine-equivalent,
and specially designed to use the properties of reversible computation to minimize power
consumption.)

Power usage?

Posted Jun 23, 2008 6:00 UTC (Mon) by jzbiciak (guest, #5246) [Link]

There sure are. One of the papers apparently describes a simple 8-bit reversible CPU.