Peter Clifton wrote:
I saw this on my old desktop computer (Nforce2 chipset, AMD XP+2800).
Not ACPI related perhaps, but definatly CPU load related. When the CPU
was "thinking", the humming stops. When it was idle, it would humm.
My presumption was that the CPU was bouncing the power rails to the
sound chip at a given frequency which was coming through. (Sound was on
the mobo, and I wasn't bothered enough to get the oscilloscope and probe
it).
It is possible that since ACPI is related to power-saving of your CPU,
removing ACPI - (and hence the power saving) stops the CPU powering up
and down / changing clock speed so much, removing the fluctuation on the
power rails.
All of this is a bit of a guess, but do see if the humming quietens
under load.
(Try the following C program...)
spinloop.c
int main( int argc, char **argv )
{
while( 1 );
}
(Compile with gcc spinloop.c -o spinloop)
Run ./spinloop
Ctrl-C will break out of it.
(Run multiple times for each CPU core you have!)
Peter C.
Yes. I definitely noticed that it's load based, however, here's the kicker.
When I power up the system with the AC adapter plugged in, and then
proceed to remove the adapter after ACPI has done its initial checks at
bootup, there is no humming sound.
Also, this hum does not occur unlesss the specific ACPI module, which is
what I expected... the processor, is loaded into the kernel.
Is there a way to attempt to load this as a module after boot time?
ACPI Support
<y> Processor
Thanks again!
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