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Thread: Can I trust motherboard voltage readings ?

  1. #11
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    Your motherboard may have measuring points. Check your manual.
    Core i7 4770K @4.3GHz + iGPU | GA-Z87X-UD4H | 2x8GB Crucial Ballistix DDR3@1600MHz
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    Samsung 840 Pro 512GB SSD | WD Black 4TB file disk | WD Red 3TB backup disk
    Fractal Design Define R5 case w/2 x NF-A14 ULN front fans | no exhaust fan; grill removed
    PSU Seasonic X-650 Gold

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    I measured the voltages of my old PC. My old motherboard is ASUS NODUS M3. (AMD Athlon 64 x2 5000+ CPU) Here are the idle results:
    HWMonitor results:
    3.3V rail --> 3.264V - 3.298V
    5V rail --> 4.947V - 5V
    12V rail --> 11.796V - 11.984V

    TT T-ECHNI-C MY62 Multimeter results:
    3.3V rail --> 3.3V - 3.31V
    5V rail --> 4.98V - 5V
    12V rail --> 11.76V - 11.79V

    I didn't risk my new PC right now.
    I measured 5v and 12v from MOLEX. It is too easy.
    But when it comes to measuring 3.3V, it is a bit harder. You can check it from 24 pin connector or 15 pin sata power connector. 24 pin connector is connected to the motherboard. So i measured from sata power connector. I accidentally touched both 3.3 and 5v positive pins. (Or created a short circuit if same probe touched both 3.3v and com pins. I don't know.) So PC closed itself. Bestec 300 12Z doesn't have any protection features as far as i know. Probably motherboard protection worked and sent 'turn off' command to the psu. My 10 years old PC working now. This mistake didn't blow up it. OMG.
    I hope I will not make the same mistake with the new PC. :S
    Last edited by Overclocked; 12-20-2017 at 04:02 PM.

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    Finally I measured voltages of the new PC which has Seasonic S12 620W.
    5v and 12v rails are again easy to measure from MOLEX. For 3.3V measuring, I used sata power connector again but in a different way. One cable has more than one connector. The last connector has some space for inserting the probes. So 5 wire are feeding 15 pins. 3.3V, 5V , 12V and two COM wires. You can check the pinouts. So you can also measure from the wire connection points instead of 15 pins.


    Here are the new pc results with seasonic s12;

    IDLE (Desktop);

    HWMonitor results:
    3.3V rail: 3.440V - 3.456V
    5V rail: 5.040V - 5.080V
    12V rail: 12.384V

    TT T-ECHNI-C MY62 DMM multimeter results:
    3.3V rail: 3.39V -3.40V
    5V rail: 4.97V - 4.99V
    12V rail: 12.13V - 12.15V

    So, I worried about 3.3V rail output because it goes up to 3.456V which is too close to the upper limit compared with ATX %5 tolerance. (3.465V) But as you can see, software results are totally wrong. 3.39V is fine value compared with ATX standards.

    Here are my system specs:
    Asus Dual GTX 1060 3 GB VGA card (NO OVERCLOCK)
    AMD Ryzen 5 1600 CPU (STOCK SPEEDS AND STOCK COOLER)
    MSI B350 PC MATE motherboard
    2 x 8 GB Crucial DDR4 memory sticks 2133 mhz 1.2V (NO OC)
    WD Caviar Blue WD10EZEX 1 TB HDD
    PC case with 12 cm 5 fans. (Variant of Gamemax Falcon)
    Seasonic S12ii 620W. Product date: May 2017
    No SSD.

    LOAD TESTING:
    Set my pc case fans to max rpm via fan controller.
    Started AIDA64 stress test (CPU, GPU, HDD and RAM stress tests started.) (I didn't start FPU and cache tests because they are unnecessary. With only CPU test, cpu consumes up to 75Watts.)

    HWMonitor software results:
    3.3V rail: 3.424V - 3.440 V
    5V rail: 5.040V - 5.080 V
    12V rail: 12.192V - 12.288V

    TT T-ECHNI-C MY62 multimeter results:
    3.3V rail: 3.39V - 3.40V (3.38V for less then 0.5 seconds i saw.)
    5V rail: 5.01V - 5.02V
    12V rail: 12.04V - 12.06V

    As you can see, software results are worrying. Voltage fluctuations are high and 3.3V goes to upper limit etc. But they are completely wrong again. Aahh crappy sensor of the motherboard.
    But multimeter results are very nice for both idle and load testing.
    So I don't need to worry about 3.3V output.

    I'm quite happy now. Yeaaah.
    Last edited by Overclocked; 12-20-2017 at 04:05 PM.

  4. #14
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    Quote Originally Posted by Overclocked View Post
    It shows 1.6V for DC 1.5V LR6 AA battery. Hmm...
    Quote Originally Posted by rafal_iB_PL View Post
    Just because battery is specced at 1.5V, doesn't mean every single one will measure exactly that right out of the box.
    No single 1.5v battery from a reputable brand will measure 1.5v when new.
    Same for higher voltage rated batteries as well.
    See attached PDF screenshot for example of discharge curves. (Panasonic LR6).
    Attached Images Attached Images
    "The one who says it cannot be done should never interrupt the one who is doing it."

  5. The Following User Says Thank You to Per Hansson For This Useful Post:

    Overclocked (12-20-2017)

  6. #15
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    Quote Originally Posted by ehume View Post
    Your motherboard may have measuring points. Check your manual.
    No info about measuring points as far as i remember. Nevermind, I measured with sata and molex connectors via multimeter.

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