# Fan questions, sensors, temperature

## while true

Ola,

I have noticed, that my fan is now (since I installed Gentoo) working in only two modes.

Not working or full speed, I guess.

On ubuntu, I have noticed that it has several stages of speed, 

but on Gentoo it is quiet (not cooling), or it is working full speed. 

Is this normal? Should it be more in order for fan to work in several stages of speed?

As I turn my laptop on, the sensor is showing amazing 45 degrees Celsius (around 113 F),

which is 10 degrees Celsius less than on Ubuntu (55 degrees Celsius, or 131 F)!!! 

(On side, xp is 75 degrees C, or 167 F on start) 

But, after 10 minutes and on, the sensors are showing incredible 80-85 degrees C (176-185 F)!!!

Although I know it is not that hot... by hand estimation...

I am using xfce, and it's panel sensor plugin. Are there some other sensor applications? 

Preferably with gui and panel applet? But shell is fine, as long as I get correct data!

Thank you.

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## Logicien

Hello,

are you using cpu frequency scaling with Ubuntu and/or Gentoo? It cool the processor using it capacity of working at differents frequency. It reduce the heat of processor and the need of the fan. That can explain the difference of temperature you see between Ubuntu and Gentoo. You can use the Linux ACPI to get the processor temperature, you have some specifics vendors acpi modules (like thinkpad_acpi for Thinkpad) that can be use to get the processor temperature and I know libsensors to that can be use to get processor temperature on machine who support it.

You have sensors-applet package for Gnome who can display those multiples way of sensing the processor heat if they are usable on your system. acpitool command line is good to get ACPI information including processor temperature. It's output is more complete than the acpi -v command line. The sensors command line is for libsensors method. On my machine all methods to get processor temperature display the same degree in Celcius.

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## BradN

There can sometimes be strange interactions between the BIOS fan support, linux ACPI, and drivers for fan controller chips (or special laptop specific drivers).  It may be worth trying turning some of the latter ones off or on in the kernel or doing some googling to find the peciuliarities of your laptop.

I ran into one machine that needed a value written to the acpi fan entry in /proc/acpi to turn the fan on, quite irritating that it couldn't be done in a generic way in that case.

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