# kernel 2.6.38 decreased my CPU temperature by 5~6C!

## lowsfer

I was using 2.6.36-r8 (I used keywords=amd64 for kernel). The temperature is ~52-53C when idle. Then I noticed that in ArchLinux and Windows 7 installed on my same laptop it is about 46-47C. I tried to find the kernel module which made the difference but failed. Then I noticed that ArchLinux is with newer kernel. So I change my keywords for kernel to ~amd64 and recompiled my kernel. I used make oldconfig but didn't find a interesting new option. So the kernel options are all by default except those imported from my 2.6.36-r8 .config file.

Now it is 46~47C.   :Surprised:   Fantastic!

I guess some improvement has been made to Intel core i7 power management in 2.6.37 or 2.6.38? I've no idea about what it is.

For guys with Core i7, get you kernel updated if you haven't yet!

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## asturm

Or in previous kernels, the sensor module was reading crap.  :Wink: 

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## PaulBredbury

Hopefully the BFS ver 0.376+ will save power even more.

I suggest you give it a try in a few days, when it's marked "stable".

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## s_bernstein

Hmm... funny. My overclocked i7 920 is at 34°C on idle. I'm still on 2.56.36-r3-tuxonice, so after upgrading to 2.6.38 my idle temps are going down to 28°C? I doubt that.

BTW If you are at 46C on idle, what are you full load temps? 85°C? I would consider a bigger cpu cooler, if I were you.

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## Anon-E-moose

 *s_bernstein wrote:*   

> Hmm... funny. My overclocked i7 920 is at 34°C on idle. I'm still on 2.56.36-r3-tuxonice, so after upgrading to 2.6.38 my idle temps are going down to 28°C? I doubt that.
> 
> BTW If you are at 46C on idle, what are you full load temps? 85°C? I would consider a bigger cpu cooler, if I were you.

 

46 is pretty high for just idle.

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## Yuu

Hi,

yes 46°C are quite high for idle temperature. But, please forget idle temperatures; only on load/burn temperatures matters. Also, the delta °C only matters (burn t°c - idle t°c), if you want to see your CPU cooler efficiency.

And what kernel module do/did you use to read temperatures ? Always coretemp ? Even on Windows 7 ? I'm asking because it seems the most reliable. There's a lot of parameters : if you use different tools, it could use different algorithms to check temperature; windows could be configured to force your CPU ton enter in C-states (C0/C1/C2 states), etc...

Oh, and keep in mind that CPU sensors are not always 200% accurate ;]

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## lowsfer

 *s_bernstein wrote:*   

> Hmm... funny. My overclocked i7 920 is at 34°C on idle. I'm still on 2.56.36-r3-tuxonice, so after upgrading to 2.6.38 my idle temps are going down to 28°C? I doubt that.
> 
> BTW If you are at 46C on idle, what are you full load temps? 85°C? I would consider a bigger cpu cooler, if I were you.

 

Sorry it's my HP ENVY laptop with i7 820QM. For an i7 laptop, I guess that temperature is normal. At full load, the temperature can be 86C (you are right here  :Laughing:  )

I think for heat transfer, you should not do such a arithmetic. For a crude estimation, the decrease should be proportional to the difference between your CPU temperature and environment temperature.

For example, if the room temperature for both of us is 25C, then you would get a 5/(46-25)*(34-25)=2.14C decrease. This is a crude estimation, for more accuracy, you need integration.

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## lowsfer

 *Yuu wrote:*   

> Hi,
> 
> yes 46°C are quite high for idle temperature. But, please forget idle temperatures; only on load/burn temperatures matters. Also, the delta °C only matters (burn t°c - idle t°c), if you want to see your CPU cooler efficiency.
> 
> And what kernel module do/did you use to read temperatures ? Always coretemp ? Even on Windows 7 ? I'm asking because it seems the most reliable. There's a lot of parameters : if you use different tools, it could use different algorithms to check temperature; windows could be configured to force your CPU ton enter in C-states (C0/C1/C2 states), etc...
> ...

 

Yes I use coretemp and lm_sensors in Arch and Gentoo. For Windows, I use hwmonitor developed by CPUID company. I didn't pay much attention to the windows result. I mainly compared Gentoo with Arch.

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## lowsfer

 *genstorm wrote:*   

> Or in previous kernels, the sensor module was reading crap. 

 

Yes maybe. But I did felt a temperature decrease on the surface of my laptop. My laptop is with a metal encapsulation, which makes the surface temperature pretty sensitive to CPU temperature.

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## aCOSwt

 *lowsfer wrote:*   

> I guess some improvement has been made to Intel core i7 power management in 2.6.37 or 2.6.38? I've no idea about what it is.

 

<joking>

If you happen to be one of genstorm's neighbour... then... you certainly noticed that external temperature dropped by 5°C too between the time 2.6.36-r8 and 2.6.38 went out.

http://www.climatetemp.info/australia/

Surprisingly... I noticed that my overclocked Core II idle ... at 2.6.34 constant... went in the same time from 24°C to 29°C...

Could be that I am living in the northern hemisphere...

Spring is back !   :Cool:   Grrreat... I am going to enjoy flowers...   :Cool: 

</joking>

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## lowsfer

 *aCOSwt wrote:*   

>  *lowsfer wrote:*   I guess some improvement has been made to Intel core i7 power management in 2.6.37 or 2.6.38? I've no idea about what it is. 
> 
> <joking>
> 
> If you happen to be one of genstorm's neighbour... then... you certainly noticed that external temperature dropped by 5°C too between the time 2.6.36-r8 and 2.6.38 went out.
> ...

 

Haha, probably.

It's going to be winter here. But I don't see much difference between summer and winter since I came to Australia, always mild temperature. I'm getting tired of it. Really miss continental climate. Come on we should have 4 seasons, not 2. The worse is, no much difference between the two.

BTW, how did you know I'm in Australia??? I didn't set anything in my profile. Are you a web admin for this forum and can see the IP?

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## aCOSwt

 *lowsfer wrote:*   

> BTW, how did you know I'm in Australia??? I didn't set anything in my profile. Are you a web admin for this forum and can see the IP?

 

 :Very Happy: 

A Gentoo's forum admin   :Shocked:   Pffieeww ! I would fear so much about its stability that I would certainly refrain from posting anything myself...   :Very Happy: 

I believe that pjp shares this fear has he keeps posting within the least critical section...   :Wink: 

Well well... I had simply inferred that someone regularly posting around 4.00 UTC was likely to be living around Australia... 

And... as I had indeed noticed a significant increase of the temperature of my cores since the beginning of the spring...

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## lexming

In my case, since I upgraded to 2.6.38, I noticed that now my laptop uses more the C6 state of its Core2, reaching a 90% use on soft load with a power consumption ranging between 10-12 W. Before it never went lower than 11-12 W.  :Smile: 

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