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Tolerance of motherboard voltage regulators that control CPU Vcore?

Discussion in 'Overclocking' started by John Doe, Feb 24, 2010.

  1. John Doe

    John Doe Guest

    For example, on a Gigabyte GA-EP45-UD3, what is the actual voltage
    range (tolerance, plus or minus) if one sets "CPU Vcore" to the
    maximum operating voltage 1.3625 for an Intel Q9550?

    Thanks.
     
    John Doe, Feb 24, 2010
    #1
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  2. John Doe

    Paul Guest

    Because the processor has a "load line", the voltage values you
    see will be all over the place. For example, at idle, you might see
    a measured voltage 0.060V above where it should be (this is actually
    at odds with what the Intel datasheet says). And when the CPU
    runs flat out at 100% load, the voltage can drop 0.150V (ballpark
    figure) below the nominally programmed value. That behavior is the
    "load line", and is different than the basic "tolerance" of the
    regulator chip itself. (Unfortunately, they don't go into details
    in the Intel CPU datasheet, as to what their objectives are with
    regard to this subject. The objective doesn't appear to be, that
    the voltage value remain the same under all conditions.)

    (Pg. 24 here, for your processor, shows the load line. For whatever
    reason, the voltage isn't allowed to be a flat horizontal line with
    respect to load current.)

    http://download.intel.com/design/processor/datashts/318726.pdf

    This is the regulator on my Asrock LGA775 motherboard, and while this
    doc doesn't answer every question you might have, it'll give you a better
    idea how complicated the answer to this question can be. This regulator
    has a "tolerance" of 0.5%, which is damned good, but that tolerance
    is just for the DAC and reference inside the regulator - it isn't a
    spec for the whole motherboard or anything. The load line kinda makes
    a joke out of that 0.5% figure.

    http://www.st.com/stonline/products/literature/ds/12187.pdf

    Paul
     
    Paul, Feb 24, 2010
    #2
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