TECHNICAL TIPS
 
     
 
 
 

 

  
 
 
[08 July 2008]

Technical Update - Intel Core 2 Duo on some Intel Motherboard

Problem:

DG33BUC/DG33FB/DP35DP/DQ35JO ….Intel Motherboards - CPU temperature sits on 67degrees when using one of the E8XXX series processors??

We did the latest updates on the motherboards but could not get past the 67 degrees on the CPU. If you stop the CPU fan the temperature starts dropping?

Conclusion :

This is the answer from Intel:

“Please keep in mind that the new Intel(R) processors are using what we call the thermal margin .
This is no longer a measurement of the temperature level the processor is running at; it is actually the total temperature left before the processor reaches its maximum recommended temperature or thermal design. The shorter the margin is the closer the processor gets to its thermal limit. If by any chance the thermal margin reaches 0 degrees Celsius the system should still not freeze but it will alarm you of overheating problems with in the processor area. In our case the thermal margin is 67 degrees that means the processor still have got 67 degrees before it is considered over heated. If you want to confirm the thermal specification of your processor, please visit the following website: http://processorfinder.intel.com/ ”

      Please note that the E6XXX is 65 nanometre Core 2 Duo while the E8XXX is 45 nm Core 2 Duo. And one of the differences between the two processor technologies is the way the processor display its temperature as following:
1.
Before the introduction of Core 2 Duo processors, our CPU's had a Thermal Diode (TD) inside the CPU which output an analogue voltage corresponding to CPU temperature. This voltage was read by the SIO (Super Input Output chip which also controls things like Mouse and KB) and then can be read by software. The problem with TD is that it was not accurate.
   
2.
After the introduction of Core 2 Duo based on 65nm, Intel has introduced DTS (Digital Thermometer Sensor), which measures the thermal margin where thermal margin is the difference between the actual CPU temperature and the maximum temperature it should reach according to processor specs which is called Tj (for T Junction). So T(DTS) = T(Junction) – T(CPU), from this equation if you have T(Junction) from CPU specs and the DTS reading which can be retrieved by reading a special register in the processor, you can get the real CPU temperature.
   
3.

Since T(Junction) varies from one model to another and even the same model but different stepping, it is highly variable and very difficult to maintain for all steppings, it is difficult to get the real CPU temperature accurately for every CPU, so Intel avoided that confusion and just settled for displaying the margin, which is all what the user needs to know because absolute CPU temperature doesn't really mean anything, but the meaningful number is how much degrees remaining before it starts throttling and overheating.
 

The article from Anandtech below in their review of 45nm Core 2 Duo explains that very well.
http://www.anandtech.com/showdoc.aspx?i=3251&p=4

This concludes that the Motherboards do not give the physical temperature of the CPU like what we are used to. It is all based on a thermal margin that is set on the processor.

For example:

All this information can be found on Intel's Website at the folowing URL: 

http://processorfinder.intel.com/List.aspx?ParentRadio=All&ProcFam=2558&SearchKey

 
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