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Re: How does one control fans?



On Wed, 2005-10-12 at 23:08 +0100, marc wrote:
> I'm gradually inching my way to total control of my laptop, but now I 
> would like a bit of peace and quiet every now and then. In XPland, the 
> fan is more off than on, in Linux, it's rarely off at all.
> 
> How do I start to get a grip on a peaceful Tux experience?

I think it could be too things: Either the system is running too hot, or
the fans kick in too soon.

If your system is really running too hot (more so than when running XP),
look at what process is taking CPU time. Or maybe you aren't using
throttling, so the CPU is always running at full speed? In that case,
enable CPU frequency scaling and make sure it runs with the right
governor (probably 'conservative').

Otherwise, maybe the thermal trip points are too low. Look
at /proc/acpi/thermal_zone/THRM/temperature to determine the temperature
according to the system. Then look
at /proc/acpi/thermal_zone/THRM/trip_points to see the trip points. In
my case, it shows something like

critical (S5):	100 C
passive:	92 C: blabla
active[0]:	66 C: blabla
active[1]:	63 C: blabla

This means that at 63 degrees, the fan (FAN1) starts blowing, at 66
degrees FAN0 also starts, at 92 degrees the system is throttled, and at
100 degrees it's turned off. Also, my current temperature is 42 degrees,
and the fans are indeed turned off.

For more information, look at
http://acpi.sourceforge.net/documentation/thermal.html

Koen



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