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VCore fluctuation on Asus A8N-SLi Premium

Discussion in 'Overclocking & Cooling' started by Havana_UK, 27 Jan 2006.

  1. Havana_UK


    Joined: 14 Oct 2004

    Posts: 4,787

    Location: location, location

    Hi folks,

    I'm getting some pretty significant VCore fluctuation on my Asus A8N-SLi Premium & A64 X2 4400+.

    I don't know if this is down to motherboard VCore reading inaccuracy, or if it's actually wobbly.

    Motherboard & CPu as stated above.
    CPU at 2.6GHz (260 x 10)
    RAM on 166MHz divider, so ~216MHz
    2x 7800GTX @ 490/1300
    Enermax Liberty 620W PSU

    I have all the motherboard power connectors plugged in - 24-pin, 4 pin 12V & Molex as well. Graphics cards each have their own PCIe connector.

    I'm using the provided Asus Probe software to measure voltages / temps. Checking VCore readings with CPU-Z (both Asus Probe & CPU-Z give the same result).

    Problem #1: VCore setting in BIOS doesn't seem to have much effect on measured VCore

    I'll elaborate. VCore at default for CPU (1.35 - 1.4V) reads anywhere from 1.39-1.42V. I can increase VCore to 1.425, 1.45, 1.475, 1.5, 1.525, 1.55, 1.575 & 1.6V. I can also go lower.

    All settings from 1.35 to 1.45 seem to read 1.39-1.42V.
    All settings from 1.475 to 1.525V seem to read 1.45 to 1.5V
    All settings from 1.55 to 1.6V seem to read 1.48 to 1.55V

    Problem #2: VCore dips under heavy load (when set high)

    I noticed this while trying to get a stable overclock over 2.6GHz.

    I can boot at 2.7GHz, and Core #2 is pretty much stable at 2.7GHz, but Core #1 needs more volts.

    At max VCore set in BIOS, if I load up either core with one instance of Prime, the VCore seems stable-ish(within the limits mentioned above), however if I load up both cores simultaneously with 2 x Prime, or 1 x Prime + 1 x Super-Pi etc, the measured VCore dips under load from say 1.525V to ~1.43V.

    My components are high quality, including (I'm sure all will agree) my PSU, but I'm concerned that the VCore seems to dip so significantly when both cores are fully loaded, and think this may be why I'm struggling to get 2.7GHz stability.

    I realise my board isn't the best clocking board (I should have gone DFI if that's what I was after), but it's still not a bad one.

    Can anyone suggest anythign that may be causing this fluctuation in the reading? Is it likely just motherboard reading inaccuracy or is the motherboard generating inaccurately? Am I just being paranoid and it's normal to expect a VCore drop under heavy load?

    I don't have access to a multimeter to take actual measurements unfortunately, but I guess I could ask around if that's essential to getting the bottom of my problem?

    Thanks in advance for any help!

  2. Jimbo Mahoney


    Joined: 18 Oct 2002

    Posts: 6,197

    Location: Belfast

    Probably just reporting badly.

    Seriously, get a multimeter - they are like £5 -£10 and WELL worth it if you are into overclocking.