# laptop with KMS heating problems

## jopeto

Hello,

I just installed Gentoo on my laptop, which has an Intel Pentium B950 processor and integrated Intel HD graphics. I compiled the kernel with KMS support and use the intel video card. I can start X just fine with the right resolution.

The problem is that the CPU temperature seems to be quite high. Currently Core 0 is showing 55deg and Core 1 is 46deg just being logged on and without even having started X. First, does it make sense that the two cores are almost 10deg apart in temperature? I use the sensors command from lm_sensor package. Is that reading accurate?

Second, I just came to gentoo from FreeBSD, where I also installed the kernel with KMS support and I got temperatures of 65deg and above, which I decided was not healthy for my computer so decided to try linux. I noticed that there are a few other threads in that forum about laptops with KMS heating. Can anyone suggest a workaround to this problem apart from scaling down the CPU frequencies? Also is anyone aware whether the linux kernel developers are aware of this problem and if any course of action is planned? I'm just a bit worried cause the temperatuer is quite a bit higher than under windows...

Thanks a lot in advance!

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## Gusar

I seriously doubt the temp has anything to do with KMS.

Compile acpi_cpufreq into the kernel, and make the cpufreq_ondemand governor the default (it's an option in the kernel config which governor should be default). That's it.

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## gorkypl

 *Gusar wrote:*   

> I seriously doubt the temp has anything to do with KMS.
> 
> Compile acpi_cpufreq into the kernel, and make the cpufreq_ondemand governor the default (it's an option in the kernel config which governor should be default). That's it.

 

Exactly the point.

Also there is nothing wrong in one core being hotter - there may be some one-threaded app running in background (check with htop) and the cooler may not dissipate heat in an uniform way.

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## Thistled

Hello jopeto

I second Gusars comment with regards to KMS not being the root cause of "heat".

You will find the CPU_FREQ_SCALING in the following location of the kernel config.

```
  | -> Power management and ACPI options      │  

  │       -> CPU Frequency scaling            │  

  │         -> CPU Frequency scaling          | 
```

Don't forget to set the "default" governor I'd suggest "ondemand".

Also, while you are in Power management and ACPI options:

```
CPU Frequency scaling  --->

 -> x86 CPU frequency scaling drivers  --->

  ->  <*> ACPI Processor P-States driver 
```

^^ This is what Gusar is referring to.

You will also need to make sure you have enabled in your kernel config (although you have probably done this already):

```
-> Processor type and features

  -> Processor Family

    -> Core2/newer Xeon
```

Then you will need to re-compile your kernel.

Do all of the above and you will have control over cpu frequency and hopefully cool down your laptop.

Once you have done all of this I would suggest moving on to Lm_Sensors.

http://en.gentoo-wiki.com/wiki/Lm_sensors

Good luck, and give us a shout if you hit any more problems.   :Smile: 

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## jopeto

Thanks a lot for all your suggestions! I'll do as you say. You guys are really helpful!  :Smile: 

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