any thoughts on why cooling fan keeps spinning up and down?

[Fernando Cassia]

On Sun, Jul 5, 2009 at 12:33 AM, Kevin J. Cummings <
cummings at kjchome.homeip.net> wrote:

> Robert P. J. Day wrote:
>
>>  this is another problem i started having with the test version, and
>> it's still happening now -- on my gateway laptop running fully-updated
>> f11, the cooling fan keeps spinning up and down with about a 3-second
>> period.  it's really kind of annoying.  occasionally, it will stop
>> completely for a bit, then it starts oscillating all over again.
>> thoughts?
>>
>
> Just a guess here, but F11 is doing more with the CPU and is causing it to
> exceed the thermal threshold more often which causes the fan to kick in?
>  Have you looked at the system temperatures while this is happening?


I noticed this here too, on a desktop, Sun w1100z with 2.0Ghz AMD Opteron.

The system is totally idle, and sometimes fan speed jumps up and down. No
keyboard activity, nothing, just the machine being idle.

It seems to me that sudden spikes in cpu activity (ie, calling the screen
saver -still uses less than 10% CPU), causes some algorithm to increase fan
speed.And then after the initial spike in cpu activity, it goes back to
normal, so the fan speed is lowered as well.

It *sounds* to me like "pre-emptive" fan enabling. As if a sudden spike in
cpu activity triggers the bios fan controls. Maybe this is related to AMD´s
PowerNow stuff?

FC
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