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Reading cpu temps in CoreTemp and RealTemp?

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January 18, 2009 2:16:22 PM

Ok, I want to read the core temps of my Core 2 Duo E6400, When using CoreTemp and RealTemp I can set TJunction Max offset. To what should I set tjunction max for correct temperature readings? I´ve seen 100 being used, but Ive also read about 85. It kinda makes a big difference on the readings.

Matt
January 18, 2009 2:46:12 PM

Maybe I should say that the stepping is B2.
Matt
a b à CPUs
a b K Overclocking
January 19, 2009 2:19:57 AM

mattswe,

Real Temp 2.90 RC9, which can be downloaded from the following Real Temp thread over at XtremeSystems - http://www.xtremesystems.org/forums/showpost.php?p=3563... - should default to 90c for your E6400 B2. This is the value Intel finally released during the second Intel Developers Forum (IDF) 2008 which was held in Taipei, Taiwan in October.

If you would instead prefer precise custom calibrations for your particular E6400, then you can perform the calibrations shown in Section 9 in the Core 2 Quad and Duo Temperature Guide: http://www.tomshardware.com/forum/221745-29-core-quad-t...

Best Regards,

Comp :sol: 
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January 20, 2009 11:00:30 AM

Ok, just so I have understood this;

1. To get right core tems for my E6400 B2 in RealTemp/CoreTemp/SpeedFan/HWMonitor I should set Tjunction max to 90 degrees.

2. Now, what temerature should I watch? The core temps not to pass 90 degrees or the cpu temp/Tcase not to pass 61,5 degrees (spec).? I have a feeling that the Tcase will pass 61,5 degrees before the Tjunction will pass 90 degrees?

Im still a little confused...

And one more question to CompuTroni, is there a list with those Tjunction max temps for different processors that Intel released?
a b à CPUs
a b K Overclocking
January 20, 2009 12:37:20 PM

mattswe,

From the Core 2 Quad and Duo Temperature Guide - http://www.tomshardware.com/forum/221745-29-core-quad-t...


Section 6: Scale

... as Tcase Max will be exceeded before Tjunction Max is reached, Tcase Max is always the limiting thermal specification.

... Scales are ordered from highest to lowest Tcase Max, according to Intel Thermal Specifications.

Scale 5: Duo
E6x00: Tcase Max 61c, Stepping L2, TDP 65W, Idle 12W
E4x00: Tcase Max 61c, Stepping L2, TDP 65W, Idle 12W
E21x0: Tcase Max 61c, Stepping L2, TDP 65W, Idle 8W
X6800: Tcase Max 60c, Stepping B2, TDP 75W, Idle 24W
E6x00: Tcase Max 60c, Stepping B2, TDP 65W, Idle 24W (Spec# SL9S)
E6x00: Tcase Max 60c, Stepping B2, TDP 65W, Idle 12W (Spec# SL9Z)<--Most Common E6400 B2
E6x20: Tcase Max 60c, Stepping B2, TDP 65W, Idle 12W

-Tcase/Tjunction-
--60--/--65--65-- Hot
--55--/--60--60-- Warm
--50--/--55--55-- Safe
--25--/--30--30-- Cool


Tcase = CPU Temperature
Tjunction = Core Temperature


If CPU temperature and Core temperatures are both calibrated, then they should have only 5c between them. There's a lot of useful information in the Guiude, including how to properly test, calibrate and monitor your temperatures, so please check it out.

Comp :sol: 
January 20, 2009 1:35:05 PM

Well, I read it but its kinda exhausting ;) 

When I set Tjunction max to 90 degrees the CPU(Tcase) always is about 3 degrees warmer than the cores (Tjunction), both when idling and when under load (Prime95). This should indicate that Tcase or Tjunction shows aprox. 7-8 degrees false, right?
a b à CPUs
a b K Overclocking
January 21, 2009 1:09:33 AM

It simply means that you need to calibrate Tcase and Tjunction, rather than accept the default "canned" values, which are seldom accurate. CPU temperature is often miscalibrated in BIOS by motherboard manufacturers, just as Core temperatures are often miscalibrated at the factory by Intel. Neither CPU temperature nor Core temperatures should be trusted or assumed to be accurate out of the box. Calibration is always necessary for accuracy, but you don't need to know Tjunction Max to accurately calibrate your CPU temperature and Core temperatures. There's another method.

Tjunction Max is not a precise value. Intel has stated that Tjunction Max varies from core to core, and from processor to processor, even within the same model and stepping, due to inherant inaccuracies in the Digital Thermal Sensors (DTS) such as deviations in linearity, slope error and calibration. Intel has also stated that the DTS was originally designed for high temperatures only, for overtemp protection such as Throttle and Shutdown. The DTS becomes less accurate at cooler temperatures, and was never intended to be used for temperature monitoring. This is why Tjunction Max is a round figure such as 90c or 100c. For your particular E6400, the actual Tjunction Max value could be anywhere from 86c to 92c, and it's not likely that yours is exactly 90c.

The Analog Diode, which measures CPU temperature (Tcase), is designed specifically for temperature monitoring, and is typically very accurate from Idle through Load, when calibrated. Unlike Tjunction Max, Tcase Max is instead a precise value at tenths of a degree such as 60.1c. Intel conducted extensive lab tests using extremely accurate thermocouples embedded in the Integrated Heat Spreader (IHS), in order to document highly accurate and repeatable results under tightly controlled conditions, which are described in great detail in processor specific Intel papers. This is why the Thermal Specification shown in Intel's Processor Spec Finder is CPU temperature (Tcase), not Core temperature (Tjunction), which is a very common misconception among many users.

According to Intel, lthe Q9650 in my personal rig is 100c Tjunction Max, yet it calibrates at 98c, and my previous Q6600 calibrated at 97c. I've tested numerous Dual and Quad Core processor variants, and they rarely calibrate precisely to Intel's Tjunction Max target values. I wrote the calibration section in the Guide specifically for SpeedFan, so that users can see the "big picture" with accurate CPU temperature, as well as accurate Core temperatures. The calibration procedure is a simple concept based on Intel ducumentation; ambient is used to calibrate Tcase Idle, then Tcase Load is used to calibrate Tjunction Load. The calibrations aren't rocket science; it's grade school math.

Countless thousands of users have successfully calibrated their rigs, but if you feel that the SpeedFan calibrations require more effort than the outcome is worth, then forget about monitoring your CPU temperature. If it's not important for you to achieve the most accurate custom calibrations for your particular E6400, then just use Real Temp's default Tjunction Max value of 90c.

Comp :sol: 
January 21, 2009 11:07:17 AM

Dont get me wrong, I sure appreciate your calibration guide, I´ve already learned from it. I was just hoping to achieve reasonable values without extesive calibration. But my temps doesnt really make sense so I guess I´ll give the calibration a try after all.

Thankyou for your answers.
!