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CPU Temp Question

Last response: in Overclocking
September 18, 2007 4:18:49 PM

I have read both "Core 2 Duo Temp Guide" by CompuTronix and "C2D Overclock Guide" by graysky... but its a bit overwhelming for a newbie like me.

I want to determine my CPU's temperature - should be easy right...

I have an INTEL E6750 CPU with a CoolerMaster Hyper TX2 cooler on a Gigabyte GA-P35-DS3P motherboard in a Antec P180B case. The CPU is at stock settings and voltage.

Ambient Temp=23.5 C

SpeedFan V4.33
Temp 1: 48 C, Temp 2: 30 C, Temp 3: -2 C, Temp: 0, Core 1: 20 C, Core 2: 20 C

RightMark CPU Clock Utility V2.25
Core Clock 2000 MHz, CPU load 3-5%, OS load: 1.5-5%
CPU 0: 20 C, CPU 1: 20 C

Since the CPU/Core temperatures above were both UNDER the Ambient Temperature of 23.5, I believe those temperature are not correct and are off by 15 C due to the difference in the G0 stepping (Tjunction Max value of 100 as opposed to 85?)

CoreTemp 0.95.4
Tjunction (max) 100 C
Core # 0: 35 C
Core # 1: 35 C

I believe CoreTemp is reporting the correct temperature for my CPU/revision/stepping.
(I also did the thing with CPUID of taking the 5th and 6th character of the string returned and converting from Hex to Decimal which yielded a value of 65 -- 41 Hex -- and when subtracted from 100 give me the 35 C reading.)

Can help a newb out and let me know if I'm understanding this correctly? Thanks!

More about : cpu temp question

a b à CPUs
a b K Overclocking
September 19, 2007 5:11:09 PM

cheapfrag, yes, you're understanding of Tjunction is correct. Additionally, your CPU (Temp 2) appears to indicate too high by +5c. Just follow through the Calibrations section of the Guide (Parts 1 & 2) to correct your Tcase.

Hope this helps,

Comp :sol: 
October 22, 2007 1:20:20 PM

CompuTronix - I finally was able to follow Parts 1-4 of your guide and I'm a bit confused by the results.

Ambient Temp: 22.2 C
CPU Temp (Temp 2 in Speedfan): 22-23 C
Core 1/2: 25 C

CPU Temp seemed to be correct (a little less than 1 C from Ambient temp)

But Core 1/2 Temps seem too low... I expected it to be Ambient + 10 C or 32 C, but instead it was only 25 C. I used Crystal CPUID per steps 3A-3H for my E6750. I got "4B" in Hex or 75 decimal and subtracted that from 100 to get 25 C. Also CoreTemp said the Core 1 & 2 were 25 C.

Core Temps in SpeedFan showed 10 C. So I assume that I need to add at least 15 for the Offset correction.

But why was my Core 1 & 2 only +3 C from ambient?
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a b à CPUs
a b K Overclocking
October 22, 2007 1:57:39 PM

cheapfrag, nice work Calibrating your temps. I think you've nailed it. The Tcase to Tjunction Delta is 10c +/-3 which means that the hottest Core should typically be no less than 29c. Either the factory Digital Thermal Sensor Calibrations for the Cores are a bit off, or you by chance have an excellent Core pair that Idle a little lower than normal, which may also indicate lower than normal Load temperatures and exceptional overclocking capabilities. Let's see the temps at Prime95 Small FFT's 100% CPU Workload. Are you overeclocked, and if so, what is your Vcore and spec's?

Comp :sol: 
October 22, 2007 2:36:27 PM

ComptuTronix thanks for helping a newb. I am not currently overclocking and the Vcore is set to normal (1.35v) for now (although it was set to 1.25v and 1.6 GHz for the Idle test).

I wanted to have a better handle on my temps before attempting to do minimal overclocking (to 3.2 GHz) and reducing my Vcore.

I will try the Prime95 Small FFT 100% CPU Workload test next.
a b à CPUs
a b K Overclocking
October 22, 2007 6:00:11 PM

Well done. Just follow through Part 5 so we can see your Load temp performance. I'm sure that your temps are within norms for your configuration.

Comp :sol: 
October 22, 2007 11:27:34 PM

I also have a problem with CPU Temp / Overclocking

I am trying to OC an E6400 to 400x8 MHz from the default 266x8MHz, and the computer would automatically restart after a few minutes when no serious load is applied. I think because it restarts only a few minutes after, it could be a temperature problem.

I have been monitoring my temperature as displayed from Core Temp. My Core#0 and Core#1 never reach above 50C, yet, my computer would restart.

Could this instability be caused by something else besides an overheat?

Furthermore, I was able to successfully OC the same machine earlier this year around March without a problem. It just seems now, I can no longer do it. I am currently OC to 320x8 MHz, and it runs smoothly.
I upped the CPU voltage to 1.3375V from the stock 1.325V without any help with the restart problem.

P.S. How do you see your ambient temperature? Do I need to buy a room thermometer? I don't think Core Temp, TAT, or SpeedFan displays it anywhere. Thanks for any help.


Gigabyte GA-965P-DS3
Intel C2D E6400
mushkin PC6400 4x1GB dual channel RAM
EVGA 8800GTS 320MB
Tuniq Tower 120
Centurion 5 Case
October 23, 2007 1:17:41 AM

Xinogage - Ambient or room temperature is measured with a room thermometer - not part of any computer utility/software.

CompuTronix - I ran the load test at stock speed (E6750 - 2.66 GHz) and voltage (1.35v) using Prime95 v25.4 for 10 minutes.

Ambient Temp = 21.8-22.5 C
Temp 2 (CPU): 45 C
Core 0 (offset corrected): 50 C
Core 1 (offset corrected): 50 C

So, my Idle to Load delta is around 25 C - does this seem acceptable (you say that 20 is typical)? I concerned about the small delta between CPU and COREs of around 2 C (idle)- 5 C (load). Is that anything to worry about?

Also, if I want to do some minimal overclocking and be at a "safe" temperature, then I should keep my CPU under 60 C and the cores under 70, is that correct?
a b à CPUs
a b K Overclocking
October 23, 2007 6:09:15 AM

cheapfrag, your temps calibrated successfully, so no worries. Your Idle to Load Delta is a little high for stock, and will exceed spec as clock speed is increased, which is normal. Idle to Load Delta can also indicate the quality of thermal contact between the CPU's Integrated Heat Spreader and the CPU Cooler's Heat Sinc, which translates into flatness, so you may want to inspect each surface.

Lapping improves Idle to Load Delta, however, it also voids warranties. My own CPU isn't perfect, as it's very slightly convex, but my Cooler was concave enough to require re-surfacing and lapping. I'm also using Masscool Shin-Etsu X23 thermal compound which improves temps better than any other product. Since I'm heavily overclocked with 1.44 Vcore, my Idle to Load Delta exceeds the 25c spec with 32c CPU and 35c Hottest Core.

As for your CPU to Hottest Core Delta at 5c, this is just outside the 10c +/-3 Parameter, which in your instance means 7c. You'll find that as you increase clock and Vcore, the Delta will also increase, so when overclocked at 100% Workload, 5c may yet become 6c. My Delta is 9c at Idle and increases to 12c at Load, but there's no need for concern that you have a C2D on the low side of spec. Just remember that CPU temp is more critical than Core temp, so yes, you're correct that 60c is a Safe CPU temp, since Intel's Tcase Max spec for the E6750 is 72c.

Before you overclock, check the CPU and Cooler for flatness. Since you have a C2D with G0 Stepping and a good Cooler, you have quite a bit of thermal headroom, so you should have very good overclocking results.

Comp :sol: 
October 23, 2007 1:15:21 PM

When I built this PC two months ago (my first build), I had a heck of a time getting the CoolerMaster Hyper TX2 snapped in -- that last pin was a pain. I only used the pre-applied thermal paste and the cooler was on and off the CPU multiple times as I wrestled with it and the tight quarters.

So I suspect that maybe the contact is not perfect between the CPU and cooler. But I'm also a little leery of removing it and re-applying a new thermal paste.

Any links on how to remove existing paste and the correct way to reapply a new paste? (Note I will not lap the CPU as my overclocking will not be extreme and I would rather not void the warranty.)
a b à CPUs
a b K Overclocking
October 24, 2007 5:59:35 AM

cheapfrag, for info on lapping, go to the Hardware - Overclocking - Cooler and Heatsinks Forum and read the Sticky's such as the following - lapped my ultra-120 extreme (pics and temp results):

Also, the following link is to Arctic Silver's website:

Although I recommend using Masscoll Shin-Etsu x23 and NOT Arctic Silver 5, Arctic Silver does however, have a good description regarding the proper removal and application of Thermal Interface Materials.

Comp :sol: