# lm_sensors-cpu Temperature lower?

## pd1986

Hello, 

I found this interesting. I installed lm_sensors, the temperature it detects is about 6 or 7°C lower than that I get from /sys/class/thermal/thermal_zone0/temp

is it correct? why?

Thanks

kernel 3.2.12-gentoo

xfce4.8

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## eccerr0r

What driver/what pathway/which sensor?

Does lm_sensors have a correction applied to it?

What is thermal_zone0 ?  Where is the sensor?  What is it measuring?

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## pd1986

 *eccerr0r wrote:*   

> What driver/what pathway/which sensor?
> 
> Does lm_sensors have a correction applied to it?
> 
> What is thermal_zone0 ?  Where is the sensor?  What is it measuring?

 

Wow~~~

All right. You could find the hardware information in the following paragraph

when I run sensors-detect, it returns

 *Quote:*   

> Intel digital thermal sensor...                             Success!
> 
>     (driver `coretemp')
> 
> 

 

but

 *Quote:*   

> Found `ITE IT8512E/F/G Super IO'                            Use of uninitialized value $_[1] in pack at /usr/sbin/sensors-detect line 2378.
> 
>     (but not activated)
> 
> 

 

I checked this file, it says this drivers it to be written

then no ISA I/O ports found, nor supported PCI bus adapters found. I don't why, I load i2c_smbus module, nothing changed. After that, because I compile the hwmon coretemp as built-in, so I could run sensors to get cpu temperatures like that:

 *Quote:*   

> acpitz-virtual-0
> 
> Adapter: Virtual device
> 
> temp1:        +48.0°C  (crit = +108.0°C)
> ...

 

the temperature is always about 6°C lower than that I found in

 *Quote:*   

>  /sys/class/thermal/thermal_zone0/

 

/sys/class/thermal/*/*

where acpitz shows the information such as fans' working status, temperatures, trip_point by which the fans are modulated.

Now I see, the temperature in thermal_zone0 is for the "Adapter: Virtual device".

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## eccerr0r

acpitz is data received through ACPI, which may have a correction applied by BIOS.  Likely it is the CPU that it's tapping from however.

coretemp is read directly from the CPUs, and does not have a correction most likely.

A lot of these CPU temperatures are not very accurate anyway, it's only there to generate a rough guesstimate at how hot the CPU is.

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