RE: High-pitch noise with 2.6.0-test11

From: Grover, Andrew
Date: Fri Dec 05 2003 - 13:54:21 EST

> [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of
> Troels Walsted Hansen

> > itself (that wasn't there with 2.4). The noise happens only
> when the CPU
> > is idle. Also, I have noticed that removing thermal.o makes
> the noise
> > stop, which is very odd. Is there anything that can be done
> about that?
> I had the same problem with my Dell Latitude C600 and newer
> kernels with
> HZ>100. The solution I found was to add "apm=idle-threshold=100" to
> the kernel commandline, to disable APM idle calls.
> You should monitor the temperature of your laptop to make sure it
> doesn't spin wildly and create extra heat if you use the same
> solution.
> Using ACPI instead of APM might also be a solution?

Here's the answer from another thread:

"It's not normal, but it means they used cheap capacitors. This is known
as the acoustic noise issue. It's related to PCB vibration as a result
of the piezo electric effect on the caps. What is the timer tick
frequency? ... The 1ms gives a nice 1kHz tone. It's related to the
voltage change of C4 exit."

Regards -- Andy
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