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Comment on "Notes on MacBook Pro Whining Sound"
by Eldho — Nov 16
This is indeed capacitor whine. I hear it on my Dell machine. However, the cause of the problem is not quite the switching noise. The CPUs have advanced power states that allow the voltage to the CPU to be lowered for a few milliseconds to save power. This is why the "fix" is to stress the CPU enough to prevent it from entering these lowered power states.

The caps bypassing the cpu voltage physically changes its length slightly depending on the voltage expressed across it. WHen the advanced power management changes this voltage, the cap changes its length accordingly. When this happens at the right intervals, acoustic noise is created.

I am going to try putting epoxy or some sort of glue that "holds the cap from vibrating".

So its not that they used cheap caps, but that this new power management scheme was introduced.

To fix it, they would have the place the caps in such a way that these vibrations cancel out - this means whole redesign of MB.
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