Identical boxes indicate a 10 degree celsius difference

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BitSink
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Identical boxes indicate a 10 degree celsius difference

Post by BitSink » Mon Jul 12, 2004 9:04 pm

Grrr, just spent an hour typing up a well-composed post only to lose it when I hit preview. <sigh> May the IE/phpBB designers & coders rot in a special hell.

The very-much-shorter-version:

Two identical boxes (MB, CPU, HSF, HSF RPMs). Temperature monitor shows a 10 degree difference in CPU temperature.

Any suggestions as to why?

TIA
-Greg

HammerSandwich
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Post by HammerSandwich » Mon Jul 12, 2004 9:35 pm

Different BIOS versions can help explain it, but you can see different numbers from truly identical systems. There is some info about this at Procooling.

msm_zgok
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Post by msm_zgok » Mon Jul 12, 2004 10:15 pm

If CPU temps is the only difference my guess would be poorly applied thermal paste.

MikeC
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Post by MikeC » Mon Jul 12, 2004 10:19 pm

There are also differences in thermal behavior of every component in your systems -- including board components, PS factors and of course the CPU.

Oli
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Post by Oli » Wed Jul 14, 2004 7:57 am

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MikeC
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Post by MikeC » Wed Jul 14, 2004 8:16 am

Oli wrote:I'd suspect poor calibration of the thermal sensor (im guessing an AMD cpu? the P4s are usually a bit better)...
Now what would make you write something so contentious? How would you show this?

The temp diode in the P4 is located way off in one corner so that it underreports the real max core temp by over 10C, as much as 15C. See the pic below, from p2. of SPCR's Unique HSF Testing Method article. It came originally from Intel Developer Update Magazine, April 2002:

Image

The top arrow shows position of thermal diode in P4 core; the middle arrow shows hottest spot.

PS -- a copy of the IDUM magazine can be found on Intel's site; I have it if you'd like to see it.

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Post by acaurora » Wed Jul 14, 2004 8:57 am

Also, not to be picky, but you didn't say identical cases. And yah, things vary all the time, despite the same product. Quality Control is responsible in companies for keeping products within certain thresholds, at least that's my understanding, and thus that's why identical "boxes" may not operate the same. Like msm_zgok also said, you can't apply your thermal paste EXACTLY the same way you did on the other box.

Oli
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Post by Oli » Wed Jul 14, 2004 9:40 am

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MikeC
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Post by MikeC » Wed Jul 14, 2004 10:05 am

Oli, the only reason I posted all that is that your comment seemed like another AMD diss w/no way to resolve it -- which then becomes a slur. I don't think there's any reason to believe greater consistency w/ Intel -- thermal diodes have been around for decades, and Intel's certainly not the only one to use them.

PS -- I admit I prefer to stick up for the underdog (in typical fashion?) ;)

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Post by luminous » Wed Jul 14, 2004 1:44 pm

I can maybe add a little to this. I got an ASUS A78Nx Delue mobo that became faulty. It was replaced for an identical model.

The difference is that before the replacement my load die temps were around 65C, now they are 75-80C. I've re-applied my HSF about 20 times with different methods and different amounts of TIM.

I've posted about this before (quite a while ago), and I received the assisstance of some of the most experienced SPCR members. In the end we concluded that the mobos were just sensing the temps differently. I used to be really concerned about this. Now I no longer care, the machine has run for 12hrs every day for 6 months and not crashed (I try to do my bit for SPCR's folding team).

I know that there are no differences in the config of my system. The difference in temps is purely down to the change in mobo. Its just the same way that the same HDDs from the same manufacturer can make different amounts of noise.

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Post by halcyon » Thu Jul 15, 2004 12:51 am

Accurate <> consistent.

You can also be consistently wrong.

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Post by luminous » Thu Jul 15, 2004 9:18 am

Yes, I'm sure that there are an awful lot of computers that show consistently wrong temps :)

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Post by wumpus » Thu Jul 15, 2004 10:46 am

There is a huge variance in the amount of temps generated by the same model CPU, for one thing!

That's primarily why some CPUs are "good overclockers" and others are "crappy overclockers." Also why Intel and AMD speed bin their chips.. they make a bunch hoping they'll all be 3800+ models, then test them to determine which will make the grade. The ones that don't run as 3800+ may run fine as 3400+ or 3000+.

Just some examples, but they are real world examples.

BitSink
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Post by BitSink » Sat Jul 17, 2004 11:04 pm

Thanks for all the responses...

I've re-seated the HSF with an absolute minimum of TIM, but have not seen any impact on the indicated temperature. <shurg>

Based on the responses to date, looks like a cross between "you pays your money and you takes your chances" and "if it works, don't sweat the details."

Thanks,
-Greg

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Post by cpemma » Sun Jul 18, 2004 11:34 am

BitSink wrote:Based on the responses to date, looks like a cross between "you pays your money and you takes your chances" and "if it works, don't sweat the details."
Don't forget "The proof of the pudding is in the eating". If a system runs stable, take that as your baseline; if a change in cooling method reduces the yemperature, then OK, but don't fret about the absolute values. That way you end up paying OTT for Arctic Platignum (contains real ink). ;)

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