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'Reversible' Computers More Energy Efficient
James Clark writes "As Congress continues work on a federal energy bill, a group of University of Florida researchers is working to implement a radical idea for making computers more energy efficient -- as well as smaller and faster." Reversible computing rears its head again.
Has anyone ever built even a very simple reversible computer? Or is this like quantum computers: all theory, no practice?
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
Isn't it just easier to use the excess heat to power a Stirling engine to recapture waste energy?
Maybe the Stirling idea is going too far.
How about a more efficient circuit? It's been awhile since college, but isn't excess heat a sign that the circuit is inefficient?
While it's not completely frivolous research, it's not the first avenue I would approach when looking at this problem. It seems more difficult and time-consuming to add in circuitry to re-use the energy to perform other actions inside of a CPU. It seems like you'd have a better chance at compounding the problem, rather than helping it.
However, make the circuit more efficient, you'll generate less heat. That would be my first goal. What kind of efficiency do they get with today's CPUs?
With this reversible thinking, I have an idea. I need a little help from the anti-SUV crowd... wouldn't all gasoline engines be better off with really big flywheels?
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(k = Boltzmann's constant, W = number of states)
Information (in bits) I = log_2 W = ln W / ln 2
Hence S = kI/ln 2 or roughly S = kI.
Heat Q = ST = kTI.
Let's say we destroy 100 gigabits of information at a temperature of 300 K. Since k = 1.38E-23 J/K, this means a heat of about 4E-10 Joules. Which is not very much, and does not really contribute to the heat produced by CPUs.
In fact, I think this is the way to find a theoretical minimum for the heat produced from information processing. We can try and make more efficient processors to get closer, just like we can increase the efficiency of engines to get closer to the thermodynamic limit.
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