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From what I've found on the internet, CPU clocks work with piezoelectric material to produce a very stable oscillating signal but those materials must change in shape or size to get a different frequency. So how does a CPU change frequency?
Do CPUs use some other kind of less stable clocks then fix them with a crystal oscillator or ...?
(I know very little about electronics, please stay simple, thanks)
Please note that I'm not asking how it is decided to change the frequency (like this question), I'm asking how the frequency change actually happens in the circuit.