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CORE TEMP. Tcase VS Tjunction

post #1 of 7
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Apparently CORE TEMP gives tjunction temps, or temps of inside each of the cores. It says for my G0 the Tjunction max is 100C. Ive read up, and it seems that the Tcase temp is usually lower than the 4 cores temps, and its the actual temp your supposed to monitor when trying to stay under the thermal spec of 72C for a q6600.

Anyone know more about this? Also, what program monitors Tcase temps?
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post #2 of 7
Pretty much any program that measures tcase has a high probability of being off. There are no sensors that do any more than estimate. If you want a ton of info about this read something like "TSK's crazy idea about tcase" or something like this. its by thesubtleknife and also retrospekt has a temp thread.
    
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post #3 of 7
If you look at diagram below you can see why Tcase can not be directly measured.

digital sensors measures temp on cores - labeled in blue

diode measures temp between cores - labeled in pink.

The max gradient from digital sensor at core to diode between cores AT STEADY STATE LOAD is ~5C. http://arxiv.org/ftp/arxiv/papers/0709/0709.1861.pdf
Temp of diode is NOT TRUE Tcase, and will read hotter than tcase on load. Have to go through more core, TIM1, and IHS to get to true tcase. (There are transient gradients MUCH higher on accelerating load, but these are not going to be seen sampling every one seconds or less as most software does, and certainly not after a few seconds when steady state has reached.)

So if your cpu temp is diode between cores, then the max gradient you should see from "CPU" to CORE is 5C with TAT, less with orthos and so on, but you ARE NOT MEASURING CORE TO TCASE GRADIENT.

If your cpu temp is mobo sensor - labeled in red, you can see it is no where near the cooling heat sink either, and once again is poorly representing Tcase.

On top of positional error, and thus nearly impossible to scale properly, diodes, unlike digital sensors, are not read directly from the cpu. mobo chips read the electrical signals, and must be calibrated properly to try and approximate tcase. But, they are really not even approximating Tcase, as they will likely read between tcase and core always, because they are not as close to the cooling heatsink.

I am sure intel is fine with telling you to watch cpu temps, since they should be higher than Tcase as they are further from heatsink (assuming no calibration errors/electrical errors, etc), and thus you are even safer.
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post #4 of 7
Quote:
Originally Posted by opt33 View Post
If you look at diagram below you can see why Tcase can not be directly measured.

digital sensors measures temp on cores - labeled in blue

diode measures temp between cores - labeled in pink.

The max gradient from digital sensor at core to diode between cores AT STEADY STATE LOAD is ~5C. http://arxiv.org/ftp/arxiv/papers/0709/0709.1861.pdf
Temp of diode is NOT TRUE Tcase, and will read hotter than tcase on load. Have to go through more core, TIM1, and IHS to get to true tcase. (There are transient gradients MUCH higher on accelerating load, but these are not going to be seen sampling every one seconds or less as most software does, and certainly not after a few seconds when steady state has reached.)

So if your cpu temp is diode between cores, then the max gradient you should see from "CPU" to CORE is 5C with TAT, less with orthos and so on, but you ARE NOT MEASURING CORE TO TCASE GRADIENT.

If your cpu temp is mobo sensor - labeled in red, you can see it is no where near the cooling heat sink either, and once again is poorly representing Tcase.

On top of positional error, and thus nearly impossible to scale properly, diodes, unlike digital sensors, are not read directly from the cpu. mobo chips read the electrical signals, and must be calibrated properly to try and approximate tcase. But, they are really not even approximating Tcase, as they will likely read between tcase and core always, because they are not as close to the cooling heatsink.

I am sure intel is fine with telling you to watch cpu temps, since they should be higher than Tcase as they are further from heatsink (assuming no calibration errors/electrical errors, etc), and thus you are even safer.
CPU temp is not measured by a mobo "sensor", the signal is taken from the CPU diode itself and converted by the super IO chip and northbridge. Intel has stated the accuracy of the thermal diode (Tcase) is +/-1c and the thermal diode is indeed between the cores at the middle of the die. You are correct about the 5c delta, but that is on small FFTs/blend on Orthos or Prime95. Intel's Thermal Analysis Tool (TAT) is made strictly for mobiles, as we all can see our desktop Core 2's are seen as Pentium M's. TAT has given the weirdest of all temps for many users, some get very low and some get very high and full load on TAT is equal to 114% load of Orthos or Prime95 on small FFTs. The delta you should see with TAT is typcially 8c and in many cases higher.

I think you made a mistake on the last part, CPU temp is the Tcase, you seemed to have said CPU temp and Tcase are different. There is only 2 temps, Tcase and Tjunction, Tjunction means core temps. I am not trying to bash you but if you think Tcase is wrong or unimportant you are going head to head against the company that made these processors, the info for Tcase is right on their site.
     
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post #5 of 7
Quote:
Originally Posted by GigaByte View Post
CPU temp is not measured by a mobo "sensor", the signal is taken from the CPU diode itself and converted by the super IO chip and northbridge. Intel has stated the accuracy of the thermal diode (Tcase) is +/-1c and the thermal diode is indeed between the cores at the middle of the die. You are correct about the 5c delta, but that is on small FFTs/blend on Orthos or Prime95. Intel's Thermal Analysis Tool (TAT) is made strictly for mobiles, as we all can see our desktop Core 2's are seen as Pentium M's. TAT has given the weirdest of all temps for many users, some get very low and some get very high and full load on TAT is equal to 114% load of Orthos or Prime95 on small FFTs. The delta you should see with TAT is typcially 8c and in many cases higher.

I think you made a mistake on the last part, CPU temp is the Tcase, you seemed to have said CPU temp and Tcase are different. There is only 2 temps, Tcase and Tjunction, Tjunction means core temps. I am not trying to bash you but if you think Tcase is wrong or unimportant you are going head to head against the company that made these processors, the info for Tcase is right on their site.
This will be my last response because I tire of the effort. I am going to stick to XS, where people actually read and understand the readily available intel docs.

Tcase is only accurately measured ~380 microns into IHS via a thermocouple, period. This is specified in nearly all the intel thermal docs WITH PICTURES.

"CPU" diode temp is not measuring Tcase at that point, ever, and on load it matters. If your cpu has a diode sensor, then temp is being measured between the cores. To go from between the cores (diode), you pass through more core, TIM1 and IHS, and intel research suggests roughly 50% of resistance is in TIM1 and IHS on load, therefore you are missing 50% of gradient, therefore you are not measuring Tcase, you are somewhat poorly approximating/over estimating it.

Intel does refer to Tdiode as "approximation" of Tcase, but in no way is it Tcase, and it will read higher than Tcase. If it read the same as Tcase, intel would not go to the trouble of boring 380 microns into IHS with a thermocouple as they explain in most of their thermal papers to tell you that is the only way to accurately measure Tcase.

Intel supplies the thermal conductivity with the formulas, you can even work it out for yourself if you dont believe intel.

Why not try answering the questions below.

Cpu temp is measured where?

If cpu temp = Tcase why does intel not just use diode in place between cores, why do they cut a 380 micron slit in cpu to measure Tcase?

If cpu temp = tcase, and cpu temp is tdiode, then tdiode=tcase, so are you saying there is no gradient on high load from between cores, across tim1 and across IHS?
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post #6 of 7
Quote:
Originally Posted by opt33 View Post
Cpu temp is measured where?

If cpu temp = Tcase why does intel not just use diode in place between cores, why do they cut a 380 micron slit in cpu to measure Tcase?

If cpu temp = tcase, and cpu temp is tdiode, then tdiode=tcase, so are you saying there is no gradient on high load from between cores, across tim1 and across IHS?
-From the diode between the cores within the die.

-Tcase is not actually measured from the slit placed in the IHS, it may have when the processor was in the testing labs but it is not used on the desktops we buy in the stores. I took my IHS right off and all temps got a huge drop, thats Tcase and Tjunction. I have seen in an Intel document myself that they have stated the diode between the cores is where Tcase is read from and because the diode is different than a DTS the signal needs to be converted by the super IO chip on your board so its readable by software. Tcase in Core 2's is the same Tcase as in Netburst CPUs, thermal diode within the die.

-This is exactly what I was arguing about in the other thread with unclewebb, I was arguing there IS a gradient but he does not seem to understand it, but you seem to understand it correctly. This is where the problem with using the IR gun lies, perhaps you can try to explain it to him.
     
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post #7 of 7
Quote:
Originally Posted by GigaByte View Post
-From the diode between the cores within the die.

-Tcase is not actually measured from the slit placed in the IHS, it may have when the processor was in the testing labs but it is not used on the desktops we buy in the stores. I took my IHS right off and all temps got a huge drop, thats Tcase and Tjunction. I have seen in an Intel document myself that they have stated the diode between the cores is where Tcase is read from and because the diode is different than a DTS the signal needs to be converted by the super IO chip on your board so its readable by software. Tcase in Core 2's is the same Tcase as in Netburst CPUs, thermal diode within the die.

-This is exactly what I was arguing about in the other thread with unclewebb, I was arguing there IS a gradient but he does not seem to understand it, but you seem to understand it correctly. This is where the problem with using the IR gun lies, perhaps you can try to explain it to him.
If you want to believe Tcase is same point/temp as Tdiode at load, despite diagram from intel (first post), so be it.

But regarding using IR to approximate core, basic physics....

Cooking one end (core at load) and cooling the other (heatsink cooling IHS) causes the significant gradient.

Core at idle, low volts, and not cooling the other end (no heatsink), the gradient will be very small, hence you can approximate core by measuring IHS under THOSE CONDITIONS. Once again, it is you that does not understand.
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