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Comment by ohiovr | Hacker News Reader

The reason computers use energy is because transistors have a finite signal rise time and are bound by ohms law. This is unlikely to ever change.

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Indeed, but smaller transistors (less capacitance, thus less charge transfer) and lower voltages can reduce the power consumption of digital circuits. Also, more efficient software could reduce the amount of switching that has to occur. And I suppose one has to consider the power consumption of some peripherals such as LCD back-lighting.

Long ago I had an internship where we were developing a battery powered microprocessor based gadget. We had a prototype with a knob for the clock speed, and we slowed down the clock until the thing started being noticeably slow. Then we chose fixed components for the same clock speed. That's how we optimized battery life.

Note that my thinking is based on relatively simplistic CMOS processors. I don't know how this applies to higher performance computers in cell phones and laptops, with dynamic memory and other goodies.

Is there such a thing as clockless parts of a cpu that only get io on a signal by signal basis?

Yes, especially in the embedded world, you can shut down portions of the system that you aren't using, or have them only wake up when some sort of event occurs.

Isn't zero also finite?

That’s true and as long as current is coursing through those poorly conducting components there will be resistive losses of some kind. The resistivity of silicon is way worse than copper. Its just that ramp on the way from nothing to everything the resistance is a lot worse. But even at zero for the gate there is going to be some leakage I think.

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