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CPU package temp is 5 deg higher than highest core temp


Mike365
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Hello,

 

I have a system based on a ASUS 99X Deluxe motherboard, with an Intel i7-5960X. Overclock around 4GHz, aiming on 7/24-duty with numbercrunching tasks (closed water-cooling).  My goal is to keep the highest core temperature well under TJ-MAX, and I think TJ-MAX is 87 degree C for the Intel i7-5960X. I have now installed a licensed version of AIDA64 Business, version 5.20.3400, to calibrate the OC.

 

My concern is that the CPU Package temperature read from AIDA64 is around 5 degrees higher than the highest core  temperatures read from AIDA64 (8-cores in the CPU). I can’t understand that and I wonder if the TJ-core measurements or the CPU package measurement in AIDA64 is incorrect. And how should the CPU package temperature be related to TJ-MAX? I attach two screenshots from AIDA64 during 100% CPU load based on my own FPU stress tasks. One figure shows the temperature graf, the other shows the temperature statistics.

 

Regards Mike

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CPU Package temperature is read directly from the processor, as an absolute degrees Celsius temperature value. No TJMax is applied on it, no conversion is made on the readout. As it is read, it is displayed.

Core temperatures are also read directly from the processor, as a relative value (distance from TJMax), in degrees Celsius. The TJMax value is read directly from the processor, and the core temperatures are calculated as:

TemperatureResult = TJMaxValue - TemperatureReading

If there's a discrepancy between the 2 different measurements, then the only one knowing the cause is the manufacutrer of your processor, Intel. We don't convert the values or alter them in any ways. All components of the formula is read from the processor, so in case the result seems wrong, one of the values provided by the processor itself must be wrong. But we have absolutely no control over that, and we shouldn't have it.

BTW, especially on low-power Intel processors (like Broadwell-U and Broadwell-Y), the CPU tends to start throttling even when the core temperatures reflect a value 5 or more Celsius lower than TJMax. One conclusion might be that the core temperature measurement subsystem (Intel DTS) isn't all that accurate, and one shouldn't count on it to provide 1-Celsius or sub-Celsius accuracy ;)

Regards,

Fiery

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