Intel TAT / CoreTemp / IDCC all different temperatures....

[bing]

In regards to the variations in the individual diodes used, I understand the nature of that but I had the impression that each DTS was calibrated on a per CPU basis already, possibly for that reason?

If the DTS read out indicates a CPU's approach to it's throttle point (which is defined by Intel themselves), what's would be the potential danger of giving a value of say 20C from 0C DTS as a rough guideline for Core2 CPUs? I think a statement like that would do much more good than harm. It would also be much better than what is currently being applied where the "actual temperature" value of 65C is used across the board regardless of whether people are "informed" about the flaws of certain applications with certain Core2 CPUs

Intel die is using MOS process, its just a type of silicon processing.

If you watch closely "almost" all other electronic chip's datasheet that is using MOS process, has the "absolute" maximum operating temperature on the junction at least 100 C or even more.

Now, Intel's specification at their datasheet stated that the maximum TC or IHS temp at TDP 130 Watt is at 54.8 C, this figures quoted from QX6800 datasheet, imo, currently this is their hottest CPU that they released for "enthusiast" market since they're supposed the owners will OC them.

What strange is, they stated the max temp at the TC (IHS) temp instead of Tjunction temp as common industry standard. Dunno why, don't ask me.

But after some "quick & dirty" thermo dynamic calculation on the IHS and of course some safe "assumptions" included, it's like they're blessing the max tjunction at approx. 85C.

If you ever did DIY in electronic or experiment by using common diode as temp probe, and more than one of course, you will know that the offset deviations for diodes as I mentioned at my previous post rougly hovering about + or - 15 to 20 C. Voila !

So simple conclusion, the accuracy for any uncalibrated diode as a temp probe is about +/- 15 to 20 C.

In the worst case scenario, if they're off by even - 20C, meaning the cpu is actually hotter 20C more than the reported temp by the tdiode, still the cpu is in the safety margin/limit before the thermal/throttling mechanism kicks in.

Another quote from Intel CPU datasheet :

The temperature at which Thermal Monitor activates the thermal control circuit is not user configurable and is not software visible

I can only speculate that Intel just use "cheap & quick" testing and verification method to determine that "throttling temp" since they're still at the safety margin.

Now other view angle, that crappy Intel stock HSF thermal resistance at full speed fan is 0.2 C/W. (this is the official number from their datasheet too)

OT, I hate that these days, popular HSF makers don't like to mention this very important specification (C/W) in their product anymore like in the old day.

Now the calculation as usual and using 130 Watt power dissipation :

IHS Temp = (Ambient Temp) + ( (Heatsink C/W) X (Power Dissipation) )

hence

IHS Temp = (Ambient Temp) + ( 0.2 C/W X 130 Watts) = Ambient Temp + 26 C

So "on paper" the max. ambient temperature for this QX6800 beast using stock HSF at 130 Watt full load is at 28.8 C

Of course we all know this is strictly "on paper", real life those limits are much higher and more relax since they just want to play it safe at the "official" paper.

Now, if the CPU is not Extreme version which has lower TDP, I'm quite confident that they (Intel) is also making a safe and calculated assumption like this :

Ignore or don't care at the tdiode values, with a cpu running "at stock speed/not OCed", with stock Intel HSF, and at full load in the room temp as high as 30 C, it is very safe to assume that the CPU is still on safe temp limit.

Don't you agree ?


This is how I see this overall issue.