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E8400 temps

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June 21, 2009 11:37:53 PM

Ok, so I am planning on OC'ing my E8400 (cooler is Kingwin RVT-12025 which is basically a clone of the Xigmatek HDT-S1283 ). The thing is I get different temp readings from various programs.



I read around a bit and it seems like RealTemp is the program that I should use. Also, some people say that the Distance to TJ Max should be changed from 100 to 95 on this one.

I just wanna make sure I get the right readings, is there any confirmation to these two statements?

Thanks.

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June 22, 2009 12:07:07 AM

The underlying issue is that the temp sensors are not properly calibrated for temps far away from Tmax. The good news is that you only need to worry about temps near Tmax, for which most/all the programs should be fine. As for 5C differences on the Tmax, I sure wouldn't want to get so close to Tmax that 5C made a difference!
June 22, 2009 2:21:00 AM

Mondoman said:
The underlying issue is that the temp sensors are not properly calibrated for temps far away from Tmax. The good news is that you only need to worry about temps near Tmax, for which most/all the programs should be fine. As for 5C differences on the Tmax, I sure wouldn't want to get so close to Tmax that 5C made a difference!


Yes indeed you are right. It's always fun to have the right readings tho :D 

Thanks.
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June 22, 2009 3:40:00 PM

You definitely want to keep tjmax at 100C, I've spoke to kevin glynn (he is realtemp ;)  ) about this and without having to explain too much 100C is more accurate than 95C, which is what earlier versions used.
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June 22, 2009 4:48:12 PM

Pamplemouss,

Real temp is the ONLY temperature monitoring utility that allows Tjunction Max calibrations AND Tjunction Idle calibrations. For your E8400 C0, Real Temp and Core Temp are using a Tjunction Max value of 100c, which is correct. SpeedFan and Everest are using a Tjunction Max value of 105c, which is wrong, but can be re-calibrated by configuring a -5c offset correction.

The flame icons on SpeedFan are just alarm limits that need to be set up, and "Aux 119c" is simply an unasigned input which can be disabled in the "Configure" button. Also, Real Temp and Core Temp report Core temperatures ONLY, while SpeedFan and Everest report CPU temperature AND Core temperature.

Here's the basics:

Core 2 Duo's have a single CPU temperature sensor (Tcase), which is the temperature shown in BIOS, and two Core temperature sensors (Tjunction). For the E8400 C0, Intel's Thermal Specification is 72c, which is shown in their Processor Spec Finder - http://processorfinder.intel.com/details.aspx?sSpec=SLA...

72c is maximum CPU temperature (Tcase Max), NOT Core temperature, which is a common misconception among many users. Also, there's a 5c Gradient between CPU temperature (lower) and Core temperature (higher), which is shown in the following Intel document - http://arxiv.org/ftp/arxiv/papers/0709/0709.1861.pdf

Maximum Core temperature (Tjunction Max) is 100c for Throttle and Shutdown protection, so the corresponding CPU temperature would be 95c, which is far too hot for sane operation. As such, CPU temperatures above 72c and Core temperatures above 77c should be considered as an "overtemp" condition.

E8400 C0 specs:

Vcore Max 1.3625
Tcase Max (CPU temp) 72c
Tjunction (Core temp) 77c

SpeedFan shows CPU temperature AND Core temperatures, while Real Temp shows Core temperatures ONLY. Both programs allow calibrations. Intel has stated that the Digital Thermal Sensors (DTS) used for monitoring Core temperatures are accurate at very high temperatures, become less accurate as temperatures decrease, may "stick" below 50c on 45 nanometer processors, and may be unreliable at idle temperatures.

On the other hand, the Analog Thermal Diode used for monitoring CPU temperature is linear from idle thru high temperatures, which is why, as per agreement with Intel, motherboard manufacturers do not include Core temperature in their monitoring utilities found on the installation disk, such as Asus Probe.

Never assume that default temperatures are accurate. The accuracy of CPU temperature is determined by BIOS calibrations, but can be re-calibrated in SpeedFan. The accuracy of Core temperatures are determined by Intel factory calibrations, but can also be re-calibrated in SpeedFan and Real Temp.

Prime95 Blend, or OCCT (Linpack), or CPU Burn Test (LinX) are cyclic workloads, which produce fluctuating temperatures. While these are useful for stability testing, they're inappropriate for thermal testing. Prime95 Small FFT's is the standard for thermal testing, because it's a steady-state 100% workload.

Since ambient temperature is a major variable, always try to test as close to 22c as possible, which is standard ambient. Also, test with case covers removed, and all fans at 100% RPM. This will eliminate cooling varables, and will provide more consistent results for comparison.

When testing, thermal saturation is reached within 7 to 8 minutes, so a 10 minute test is adequate. Keep in mind that and even the most processor intensive games or applications will rarely exceed 70% to 85% sustained workload.

From the Core i7 and Core 2 Temperature Guide: http://www.tomshardware.com/forum/221745-29-sticky-core...


Scale 2: Duo
E8x00: Tcase Max 74c, Stepping E0, TDP 65W, Idle 8W
E7x00: Tcase Max 74c, Stepping R0, TDP 65W, Idle 8W
E7x00: Tcase Max 74c, Stepping M0, TDP 65W, Idle 8W
E5x00: Tcase Max 74c, Stepping R0, TDP 65W, Idle 8W
E5200: Tcase Max 74c, Stepping M0, TDP 65W, Idle 8W
E4700: Tcase Max 73c, Stepping G0, TDP 65W, Idle 8W
E4x00: Tcase Max 73c, Stepping M0, TDP 65W, Idle 8W
E2xx0: Tcase Max 73c, Stepping M0, TDP 65W, Idle 8W
E8600: Tcase Max 72c, Stepping E0, TDP 65W, Idle 8W
E8xx0: Tcase Max 72c, Stepping C0, TDP 65W, Idle 8W<--E8400 C0
E6x50: Tcase Max 72c, Stepping G0, TDP 65W, Idle 8W
E6540: Tcase Max 72c, Stepping G0, TDP 65W, Idle 8W

-Tcase/Tjunction-
--70--/--75--75-- Hot
--65--/--70--70-- Warm
--60--/--65--65--Safe <--
--25--/--30--30-- Cool


For more detailed explanations, please refer to the Temperature Guide.

Comp :sol: 
!