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My software temp/ physical probe accuracy experiment

By KingCody · 9 replies
Jul 19, 2006
  1. Hi all :) I am hoping that this may help some people who are wondering about the accuracy of software based temp monitoring programs (MM5, speedfan, etc.)

    My software temp sensing experiment:

    my case has a cheap 3-probe temp sensor built into it. a while after i got it i borrowed an infared thermometer (Extech 42500 Digital IR Thermometer) from my brother in-law to see how accurate my case sensors were. which I could then compare to software based temp monitoring programs.

    i had one of the temp sensors glued to the PCB of my AthlonXP 2600+ with the tip of the sensor physically touching the CPU die. also, I wired the case's LCD temp display with a 12v power pack from an old police scanner so that it would stay on constantly, and not shutoff with the PC.

    since I obviously could not verify the temp of the die via the IR with the heatsink on, i removed the heatsink (and thoroughly cleaned the die).

    to avoid overheating the CPU, I set my mobo set to shut down when the CPU reached 65C (the lowest setting possible). the max die temp for that processor was 95C so I wasn't too worried about it.

    I turned on the PC and within seconds it shut down. according to the BIOS setting, that would mean it should have heated up to 65C... yet my temp sensor only read 56C and the IR read 58C. (i will assume that the IR is more accurate than anything else i had access to) that's a difference of 7C. after a few more tries i had found that my temp sensor was always 1C-2C lower than the IR reading (a negligible amount).

    I now trusted that my case's display was accurate to within 1C-2C of the IR, which was better than I expected.

    i then reinstalled the heatsink and booted into the BIOS. the BIOS read a constant 43C, and my LCD display read a constant 39C (the laser would have read 40C-41C). so that proved (to me) that the BIOS was reading the temp about 2C too high. no big deal, but this wasn't stressing the CPU

    i then booted into windows and monitored it through MM5 and speedfan. i ran halo, F.E.A.R., and superPI. the software temps were all over the place. speedfan read 3C-8C higher than my LCD. MM5 stayed more consistent but still read 6C-7C higher.

    the bottom line... software temp monitors are not accurate enough to rely on. they can be useful as a "before and after" comparison tool to see if a change in your cooling made any difference, but that's about it.

    I hope this was helpful (or at least entertaining.. lol :haha: ) hopefully i got all the numbers right because i was going off a notepad file which has the temps on it (i had done this experiment quite some time ago)

    cheers :wave:
  2. zephead

    zephead TechSpot Paladin Posts: 1,569

    some BIOS programs shut down the system is no processor fan is detected, if you unplugged the HSF from the motherboard this could have caused the system shutdown.
  3. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    It was very helpful, and very very entertaining lol :haha:

    Cheers :)
  4. KingCody

    KingCody TS Evangelist Topic Starter Posts: 992   +8

    good point, but the shutdown was indeed caused by the CPU overheating. there was a BIOS setting for a "no-fan/fan failure shutdown" however this option was disabled.

    thanks for pointing that out :)

    haha, glad to hear it... i think :rolleyes:
  5. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    Hey Kingcody !

    I have a little question for you. My father has a Biostar mobo (I don't remember the model :p), and he has a Celeron D (that almost burned out), but his new mobo is reporting a CPU temp of 39°C. That's not correct, because he had a MSI mobo, that reported a 55°C idling temp. Obviously, 39°C is way too cool for a Prescott CPU using stock cooler.

    Is there an easy way to know the real CPU temp? How much would it cost?

    Thanks! :)
  6. CMH

    CMH TechSpot Chancellor Posts: 2,039   +9

    Lol, it'll cost a bunch, getting some good equip.

    I wouldn't bother, its not giong to be very different from the correct temp. And unless you're going to do something extreme, you wouldn't need to know the correct temp anyway.
  7. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    Thanks. I think I won't get it :p It should be expensive. I should better play Half-Life 2 instead of bothering with dumb things :)

    Thanks anyway!
  8. joked u 2

    joked u 2 TS Rookie Posts: 128

    actually if you want some equmient for cheap that works... i don't know if you have a sears around but i got a mulit-meader that has a temp. probe. or you can get a infared heat therometer at
    $40 !!1 . any thing more accurate will be expensive.
  9. wolfram

    wolfram TechSpot Paladin Posts: 1,967   +9

    Thanks for the suggestion :) Fortunately, I have a sears close to my house.
    That seems to be a good choice.

    I'll see if I can check it out.
  10. joked u 2

    joked u 2 TS Rookie Posts: 128

    ya good the multi meter i got at sears was like $40 and does ac/dc has a temp probe and it auto rangeing and is all didital. also very recentily i have came across a multi meder at either radio shack or harbor freight for like $5 and has an rs-232 input/output. i know someone who has it but i dont think it has a temp probe.
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