system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what physically determines the speed of a processor?
gpt
Good question :-)

Processors are large collection of transistors coupled together by small metal (copper? gold? aluminium? magnesium?) paths in new and ingenious ways, as such we need to understand how their physical behaviour:

A transistor works by saturating a part of it with enough electrons or removing enough electrons from that part so that the other part of the transistor will start or stop conducting. This takes time, but the smaller the transistor the faster it goes. But the smaller the transistor is, the more weird quantum related issues show up.

The paths which connect everything are laying next to each other or crisscross over each other and the magnetic fields generated by these paths can interfere with the other paths. The smaller you make the distance between the paths, the more interference. So you need enough space there.

The clock signal on which the processor works needs to be everywhere more or less at the same time, otherwise it could be that your transistor logic is getting confused and 1 + 2 ends up as 4. The faster the clock signal, the less time you have to get it all in the right state, so overclocking is not guaranteed to be a working scenario.

The smaller the transistors are, the less they are able to deal with heat. For a faster clock speed, more heat is produced. The lower the working voltage, less heat is produced. But the lower the voltage, the less tolerant the transistors becomes to interference.