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JGonthier
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Joined: 06 Feb 2005
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PostPosted: Mon Feb 14, 2005 12:04 am    Post subject: fan activation Reply with quote

I noticed that Gentoo likes to activate the fan in my PowerBook more often then Mac OS X does. In fact, it is almost activated as soon as KDE has finished initializing. I am currently using the 2.6.10 kernel. Has anyone else had these observations?
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Maintenant
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Joined: 18 Jan 2005
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PostPosted: Mon Feb 14, 2005 10:42 am    Post subject: Reply with quote

Yes, I've made similar observations with my iBook. But, if you observe carefully, you'll come to realize that with MacOSX your powerbook actually becomes a lot hotter before the fan is activated. The kernel module responsible is the adt76x (or something like that). Unfortunately, I haven't found a method yet to control its speed manually. It's either set to 0 or to a very high number of rotations per minute. Sometimes, my fan rotates like crazy....
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HighOnBonsai
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Joined: 05 Jan 2004
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PostPosted: Mon Feb 14, 2005 10:48 am    Post subject: Reply with quote

Same experience here on my Powerbook: This is because of the therm_adt746x module which is very paranoid regarding the CPU temperature. You can remove the module by default and only insert it during long compilation sessions. I had my PB running a long time without the therm-module with no problems. But in general be careful: The powerbook does generate a lot of heat without the therm-module! :-)

But it's funny that the KDE init procedure generates so much load that the fan goes on... :-D No problems with Xfce4 here: Fan only goes on only during compilation sessions!


Christopher

BTW: In the past it was possible to control the fan speed by manipulating the following file:

Code:
/sys/devices/temperatures/specified_fan_speed


The following set the fan speed to 128 (which is the half of the maximum speed):

Code:
echo 128 > /sys/devices/temperatures/specified_fan_speed


But this is somehow disabled or broken now...
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colinleroy
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PostPosted: Tue Feb 15, 2005 10:57 am    Post subject: therm_adt746x explanations Reply with quote

Hi,

this isn't broken, this just has changed in 2.6.10. specified_fan_speed now holds the starting speed. Default is 64. The fan speed will gradually rise with temperature from specified_fan_speed to 255. The fan starts when the temperature reaches the limit (cpu_limit or gpu_limit, whichever is first), and reaches speed 255 when the temperature exceeds limit+8 (centigrades degrees).
You can change specified_fan_speed on the fly ("echo XXX > /sys/devices/temperatures/specified_fan_speed") or when loading the module ("modprobe therm_adt746x fan_speed=XXX").

Also, the limits are, by default, 50°C for CPU and 70°C for gpu. You can alter them if you prefer that the fan starts later (or sooner) by using the limit_adjust parameter ("echo X > /sys/devices/temperatures/limit_adjust" or "modprobe therm_adt746x limit_adjust=X"). The limits will then be 50+X and 70+X. For example, using

modprobe therm_adt746x fan_speed=32 limit_adjust=-5

will make the fan start at speed 32 when the CPU reaches 45°C.

Hope this helps!
Colin
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