# Lenovo T520 CPU Fan too slow at Mode 7



## Pummelchen (Jul 25, 2019)

Hello,

on a old Lenovo T520 I noticed that to set the CPU fan to ..


```
sysctl dev.acpi_ibm.0.fan=0
sysctl dev.acpi_ibm.0.fan_level=7
```

.. results into an RPM of ca. 3300 where as the fan max is in the 5500+ area. In Windows with tpfancontrol the max rpm's can be set. I will test this issue with Debian soon.
I use the notebook for heavy tasks and need maximum cooling, I tested to reduce clock rate and still the CPU area gets very hot. 3300 simply is too slow.

The key question is where is the rpm rate in fan_level mode 7 defined ? I'm happy to modify that value and recompile if that would work.

Many thanks,

Pummelchen


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## SirDice (Jul 26, 2019)

According to the acpi_ibm(4) man page a level of 7 should be somewhere around 4300 RPM, but that's for the T41p. I'm not sure where this is set but I suspect the numbers are hardcoded. You may want to have a look through the source code of the acpi_ibm(4) module.


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## laufdi (Aug 28, 2019)

I have the problem on a T460 that the fan_level makes no difference, either from 1 to 7 the fan is on, at about 4300 RPM, or off.
.. correction: too little difference, from 4250 to 4780 RPM.


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