[Q6600] high temp on CPU, not on cores ?

[D66]

Hi there,

Recently i bought a Q6600 G0 and overclocked it to 3,2Ghz (9x356). Upped the Vcore to 1.352 volts. Its being air cooled with a Xigmatek HDT S1283.
I thought all was well with temps, Speedfan shows on idle:

CPU: 37C
Core0: 34C
Core1: 34C
Core2: 24C
Core3: 23C

On normal everyday use i dont see temps above 60C, neither on CPU or Cores.

But...

Yesterday i played GTA IV for about 4 hours and when i got back to my desktop i noticed Speedfan showing a staggering 81 C on CPU and also showed it maxed at 88 C.
Now that would be too hot i guess but here's the thing i do not understand: Maximum temp on Core0 (always the hottest core) didnt go above 57 C.

So, my questions to all reading this post:
- What could be the reason for this huge difference in core- and cpu temperature ?
- Should i worry about cpu temperature or only about core temperature ?

Thank in advance!


sysspecs:
CPU: Intel Q6600 G0 @ 3204MHz (9x356) @ 1.352 Vcore
Cooling: Xigmatek HDT S1283
Mobo: Asus P5K Pro
Mem: OCZ Reaper 4GB DDR2-1067 @ 712 @ 5-5-5-15
VGA: ASUS ENGTX260 896MB (NVIDIA GTX260) @ stock
PSU: Antec NeoPower 550W

 

[burebista]

Rely only on core temperatures. They are reads directly from CPU.
That CPU temperature is TCase and it's calibrated through BIOS by every manufacturer. Sometimes glitches could interfere with normal readings.
For example my E8400 on P5Q-E from time to time show me 111°C on CPU temperature but RealTemp/CoreTemp shows normal 28-30°C.
To be sure on core temperatures run 5-10 passes of LinX and watch core temperatures with latest RealTemp.

 

[D66]

Ok, i never used RealTemp because the version i tried showed temperatures way lower than Speedfan and CoreTemp. But this version shows the same temps as Speedfan.

Core0 maxed at 65C using LinX, about the same as running Prime95.

You say TCase is being calibrated trough BIOS by manifacturer. Intel says TCase for the G0 Q6600 shouldnt go above 71C. Since TCase on my rig showed 88C max, does that mean Asus didnt calibrate it correct on this mobo ? That would be wicked.
So if i understand correctly there's no way to check if TCase does indeed stays within Intel's specs ?

 

[burebista]

Core0 maxed at 65C using LinX, about the same as running Prime95.

Hmm, you should have at least 6-7°C more with LinX.

Don't bother with TCase, TJMax or anything. Keep an eye on distance to TJMax and try to keep it >20-30 and everything is fine.

 

[D66]

Hmm, you should have at least 6-7°C more with LinX.

Could be true, maybe i remember it wrong but i thought i saw core0 maxed at 65C when running Prime95 for an hour. Might test it again sometime.

Don't bother with TCase, TJMax or anything. Keep an eye on distance to TJMax and try to keep it >20-30 and everything is fine.

/me is off removing CPU temp reading from Speedfan.

Thanks a lot for your replies !

 

[burebista]

You select max memory available in LinX? Best results (a.k.a. more heat) are in X64 SO and 4GB RAM (or more) though.

 

[D66]

You select max memory available in LinX? Best results (a.k.a. more heat) are in X64 SO and 4GB RAM (or more) though.

Whoa...

Selected max on mem (using 2855 MB), temps maxed at 72,72,63,63
1 hour of Prime95, using large FFTs, temps maxed at 61,61,53,52

Quite demanding on the cpu, that LinX. Maybe these temps are high but i guess there's still nothing much to worry about, since Distance to TjMax is still 28 in worst case scenario.
Besides that this machine isn't stressed this much on normal day-to-day usage.

But i guess i can forget about clocking this cpu any higher on air then.

 

[burebista]

LinX is worst case scenario, Prime95 is daily use. You can OC and use Prime95 to heat up (use Small FTTs) your CPU, that's a more realistic scenario.
But try not to surpass those 20C distance to TJMax. Below 10-15C distance to TJMax I don't feel very comfortable on long term.

 

[D66]

Aight. I'll see how high i can get this cpu running stable without breaking that 20C Distance to TjMax barrier.

What still is a mystery to me is that huge difference from TCaseMax specified by Intel (71C) and my mobo/Speedfan reported 88C earlier.
Shouldn't the cpu throttle itself back when it crosses that 71C? Or does it only do that when it reaches TjMax ?
And if it's truely a miscalibration by Asus, is there any way to recalibrate it myself ? Or can this only be done by a BIOS update from Asus ?

(i know you told me i don't need to worry about TCaseMax, and i don't, but i just like to understand. )

 

[burebista]

Here you have some Intel documentation. On appendix D you'll find the method to properly install a thermocouple for Tcase measurement.
To spare you of a boring reading I'll give a quote from unclewebb (RealTemp developer) at my question about TCase and TJMax.

To me, TjMax is the important number. Thermal throttling and thermal shut down is always based on this number. A Core based CPU generally starts to thermal throttle when the Distance to TjMax number gets down to about 3 or 2. When it gets about 25 or 30 degrees hotter than that the CPU will automatically shut down to prevent it from burning up.

The Tcase specification is designed for system builders. The proper way to measure it is to cut a groove into the top of a CPU and run a thermal couple with a calibrated sensor being placed at the geometric center of the CPU. This sensor must be flush with the IHS so that the heatsink can be reinstalled. When the system builder is testing at the thermal design power of the chip, he needs to make sure that the case and case fans and etc., that he has chosen are able to keep the CPU below the Tcase max temperature. Most users don't understand that when you are running a program like Prime95 small FFTs or Linpack, you are going beyond the thermal design power level so extra heat should be expected. Intel picked the Tcase rating because they know that if you stay below that number during testing then there should be very little chance that a computer will reach the thermal throttling point, even on a hot day while running some stressful applications.

 

[D66]

That one quote clears up a lot of my questions. Thnx.

Lol, cutting a groove in the IHS is not something i'd like to do on my brand new shiny cpu. Maybe that's something fun to do when i buy a new i7 or something in a couple of years.