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Somebody I know claims that the only moving parts of a CPU are electrons.

Is that true?

I've tried to find an answer myself but I only get resources that describe at length how CPUs work in general without getting into this specific question.

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    $\begingroup$ if you go into the subatomic realm, then everything moves $\endgroup$
    – jsotola
    Feb 25, 2023 at 4:42
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    $\begingroup$ generally there are no moving parts in a integrated circuit thats not a mems one. But if you define electrons as moving then your defining movement in a way thats non conventional and then the answer is everything moves, not just in the cpu but everywhere. Thus this becomes a problematic take on the word move. $\endgroup$
    – joojaa
    Feb 25, 2023 at 6:19
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    $\begingroup$ Usually, you care about "moving parts" because you are interested in in wear and parts count with respect to cost, complexity, and reliability. Electrons don't satisfy any of this criteria. If you count electrons as a moving part then you should probably count light through a lens and the fuel flowing through the engine as a moving part as well. Basically, why are you interested in the classification? If you don't know then it means it is a meaningless exercise in classification without purpose. $\endgroup$
    – DKNguyen
    Feb 25, 2023 at 19:46
  • $\begingroup$ Move implies physical movement. And all electrons are always in motion, so it is dificult to define atomic movement of electrons from atom to atom as movement. $\endgroup$ Mar 2, 2023 at 20:43
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    $\begingroup$ The holes move too. $\endgroup$
    – Transistor
    Mar 28, 2023 at 13:09

3 Answers 3

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CPUs are solid-state electronic devices, and their operation relies on the flow of electrons through transistors and other electronic components, rather than any mechanical moving parts.

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Sounds to me like a misconception, both of how currents flow and what happens inside an integrated device physically. A few examples.

Energy transport actually happens via the electromagnetic field, see the concept of the pointing vector.

Electromigration is a visible effect from electrons moving aluminum in interconnection layers. Think of bombarding Al, which creates e.g. both whiskers and voids/holes. In some processes those whiskers even penetrate insulating nitride layers. electromigration

Very high electric fields are normal on chip-level, due to the very small dimensions $d$: $E = \frac{V}{d}$, often close to breakthrough conditions. So all sorts of transports do happen, be it inside a junction, breaking through a thin gate oxid etc. No high local fields, no peration of the IC.

Over lifetime things degrade, e.g. become porous, start moving etc. Think of all mechanical empacts available around an IC over 10 years, and think of all way to creat mechanical motion by any effect you can provide from the inside. E.g. most IC's are operated with non-DC signals, weation is normal, so which paves the way to electromotorical effects. Heat creation is normal, so think of boiling effects under the encapsulation (leave some water vapour during a processing step, ond off you go over lifetime).

Just the beginning of a long, long list ...

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All solid-state devices have no moving parts as would a machine with gears and levers, etc. So it is true that the only thing in a CPU that moves are electrons and holes residing inside the transistor junctions.

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