# core2temp - how accurate are these?

## adrin

how accurate are temperatures returned by core2 temp? They seem weird to me....

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## region-g

Compare them with bios provided temps and respond, you may

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## gerard27

I own an Asus P5W DH board.

Whether I read the bios temp or gkrelm they are weird.

When I turn on the box the temperature is some 4 or 5 degrees lower

than the temperature in the room! ( centigrade)

Gerard.

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## region-g

What about a simple comparison between the bios and sensors temps?

Cause my computer has more that 5degrees C than my room has

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## Paapaa

 *region-g wrote:*   

> Compare them with bios provided temps and respond, you may

 

BIOS sensors are crap. Core 2 Duo processors give you quite good and comparable readings. So use the processor temps if available. Forget BIOS results as they can be over 10 degrees celcius off. And yes, with conventional cooling your CPU has to be at least a few degrees hotter than ambient air.

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## adrin

the problem is that bios temps are like 45 degrees and the ones showed by lm_sensors are 50-67 degrees which is too much for c2d processor... i do not know if i it is correct, if it is i have to change cooling ASAP

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## Paapaa

I'd trust the core sensors. 67 is a bit high but the CPU should handle it.

0. What is your room temperature? (This is the base of all readings...)

1. Which processor you have?

2. Have you overclocked or overvolted?

3. Which cooling do you use?

4. Did you apply enough thermal paste and is the cooler properly in place? And is the fan working properly?

5. Do you have any stability issues?

I have an overclocked C2D E6400@3GHz and it runs at 40 C in idle. In max load it goes up to 55 C. I have maybe the best cooler on the market: Thermalright Ultra-120 with a Nexus fan@1200rpm.

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## adrin

i am running E2180 1800@2500 MHz on box cooler/box thermal paste.

I think i will switch to Freezer 7 Pro and apply a better paste

EDIT:

running acovea compilations

CORE0: 71.00 degrees

CORE1: 75.00 degrees

 :Rolling Eyes:  does linux core2 temp sensor show good values on your computers?

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## Lawless

After going from 2.6.24 to 2.6.25.4 coretemp reports about 10-15 degress more on my Core2 than before. While the bios shows something around 50 degrees coretemp is at 60 or more.

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## MostAwesomeDude

My laptop idles at 65-75 C, and with one core pegged, is about 85-90 C. Pegging both cores usually gets it above 100 C. (For reference, critical on laptop Core 2 Duos is 105+ C.)

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## SeaTiger

My Q6700 show ~26C-32C with no load. When compiling it can go up to ~45C.

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## Monkeh

 *adrin wrote:*   

> the problem is that bios temps are like 45 degrees and the ones showed by lm_sensors are 50-67 degrees which is too much for c2d processor... i do not know if i it is correct, if it is i have to change cooling ASAP

 

coretemp is accurate (at least on 65nm CPUs, I'm not sure if it is on 45nm models). 50-67C is safe for a C2D, but I'll guess you're using the stock heatsink from those temps, which is more than a bit crap.

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## Link31

 *Lawless wrote:*   

> After going from 2.6.24 to 2.6.25.4 coretemp reports about 10-15 degress more on my Core2 than before. While the bios shows something around 50 degrees coretemp is at 60 or more.

 

I experienced the same problem. I read somewhere that this is a new bug in the kernel code.

Here is a patch I made (a bit hackish  :Wink: ) that seems to "fix" this problem:

```
--- a/drivers/hwmon/coretemp.c  2008-05-11 19:06:11.106236196 +0200

+++ b/drivers/hwmon/coretemp.c  2008-05-11 19:06:54.873240942 +0200

@@ -192,9 +192,9 @@ static int __devinit adjust_tjmax(struct

                        dev_warn(dev,

                                 "Unable to access MSR 0xEE, for Tjmax, left"

                                 " at default");

-               } else if (eax & 0x40000000) {

+               } /* else if (eax & 0x40000000) {

                        tjmax = 85000;

-               }

+               } */

        } else {

                dev_warn(dev, "Using relative temperature scale!\n");

        }
```

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## Monkeh

 *Link31 wrote:*   

>  *Lawless wrote:*   After going from 2.6.24 to 2.6.25.4 coretemp reports about 10-15 degress more on my Core2 than before. While the bios shows something around 50 degrees coretemp is at 60 or more. 
> 
> I experienced the same problem. I read somewhere that this is a new bug in the kernel code.
> 
> Here is a patch I made (a bit hackish ) that seems to "fix" this problem:
> ...

 

It is not a bug. Please go read up on how the Core 2 DTS works before advising people to modify their drivers. The fact that the temperature is that far above what the board sensor reports indicates it's most likely correct.

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## Link31

 *Monkeh wrote:*   

> It is not a bug. Please go read up on how the Core 2 DTS works before advising people to modify their drivers. The fact that the temperature is that far above what the board sensor reports indicates it's most likely correct.

 

I can remember having read that this was really a bug. But I can't remember where.

If you have any other information, please post a link. But I'm running a kernel with this harmless hack for several weeks without any problem.

edit: okay I found it: http://lkml.org/lkml/2008/4/18/190

I'm not sure if this could be called a bug. It seems that there is no reliable way to retrieve the temperature scale on Intel processors. So the kernel code may or may not be wrong, depending on your preferences. I prefer seeing lower temperatures, but I hope they will find a better way to detect the scale.

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## Monkeh

 *Link31 wrote:*   

>  *Monkeh wrote:*   It is not a bug. Please go read up on how the Core 2 DTS works before advising people to modify their drivers. The fact that the temperature is that far above what the board sensor reports indicates it's most likely correct. 
> 
> I can remember having read that this was really a bug. But I can't remember where.
> 
> If you have any other information, please post a link. But I'm running a kernel with this harmless hack for several weeks without any problem.
> ...

 

The lower temperatures you're seeing are incorrect. You are seeing false temperatures.

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## Link31

How do you know they are wrong?

Again, if you have a reliable source, please post a link here.

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## MostAwesomeDude

 *Link31 wrote:*   

> How do you know they are wrong?
> 
> Again, if you have a reliable source, please post a link here.

 

You didn't read the LKML thread you linked to?! Astounding.

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## Link31

Well, at least I post links, while you don't.

http://lkml.org/lkml/2008/4/29/663

http://lkml.org/lkml/2008/4/30/28

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## Monkeh

 *Link31 wrote:*   

> How do you know they are wrong?
> 
> Again, if you have a reliable source, please post a link here.

 

Because there is no way the core temperatures are the same as the board sensor temperatures. The core sensors are inside the core, the board sensor is on the surface of the board under the plastic socket, which does not transfer heat well. There is no way the core temperatures are going to be any less than 5C higher than the board reading, unless you're using water cooling or similar.

I don't have any links for you, what I have is an understanding of thermal behavior, CPU design, and a touch of common sense.

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## Workaphobia

Huh? Are we talking about sensors provided on the motherboard, or the readings reported by the sensors in the processor and displayed in the BIOS? Are the readings in the BIOS about the processor accurate or not?

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## Monkeh

 *Workaphobia wrote:*   

> Huh? Are we talking about sensors provided on the motherboard, or the readings reported by the sensors in the processor and displayed in the BIOS? Are the readings in the BIOS about the processor accurate or not?

 

No, they are not. The BIOS sensors are on the motherboard. They do not (at least none of the ones I've seen) read the sensors in the CPU.

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## LinuxDude

I am going to have to agree that the temps that 2.6.25 is reporting are incorrect for my E6700 cpu. The older Core 2 had a Tjmax of 85C whereas the newer chips like my E6750 have a Tjmax of 100C. The new kernel is reading 15 degrees hotter than it should be. I can confirm this by using CoreTemp for windows which was the original core temp program. The values are exactly the same using the old kernel with the 85C Tjmax. The new kernel is incorrect for some chips. There is no way that my 6700 is idling at 61C while my 6750 is idling at 38C. Same room, same cooling, etc. The 6700 would usually run 2-3 degrees hotter than the 6750, but certainly not over 20C. The older core 2 has a Tjmax of 85C. The kernel guys need to talk to the devs at http://www.alcpu.com/CoreTemp/

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