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Overclocking vCore increase under load?

Discussion in 'Hardware' started by Fingers66, 30 Apr 2010.

  1. Fingers66

    Fingers66 Kiwi in London

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    Hiya,

    Hopefully someone can advise me on the situation I have...

    First some background:

    I am O/C'ing the following:

    E6600 65nm @ 1.375v
    Asus P5N-E SLI
    Corsair TWIN2X4096-6400C5DHX @ 5-5-5-18 @ stock speed (m/b won't take over 1000mHz)

    I had numerous Prime95 stability problems that were only resolved by upping the vCore to 1.4v. This obviously had heat ramifications. I also noticed a huge vdroop.

    After some research, I found this is common on this m/b. I then found this http://www.overclock.net/intel-motherboards/146744-asus-p5n-e-sli-650i-thread.html which shows a vdroop mod (post #3). This involved rubbing a pencil across a resistor on the m/b.

    Damned! It worked! Stable at 1.375v (BIOS) or 1.36 (CPU-Z) so far and I intend to incrementally reduce the vCore to further reduce temps (65C under Prime95).

    The thing is...I now have a vCore INCREASE under load. It increases from 1.36v to 1.4v using Prime95.

    Has anyone seen a vCore increase under load?

    Regards,

    Fingers66

    btw: great forum, been lurking for yonks but only just joined...
     
  2. thehippoz

    thehippoz New Member

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    thing with the pencil mod is there is a voltage spike every time the cpu loads.. that's why vdroop is built in by design

    so you risk electromigration every time you load the cpu.. the way it's designed- the voltage you set in the bios accounts for this spike

    so let's say you have 1.4v on the e6600 but it loads around 1.36.. the engineers are accounting for the .04v spike that happens on load and it guarantees your chip won't see anything above 1.4v

    with pencil mod.. you've simply increased the voltage to the chip at the same setting- so if you did it right (you have too much pencil on there right now)- you would show 1.4v at load instead of 1.36 before the mod

    the problem is there's still that .04v spike.. so everytime you put a load on the cpu after the mod, it's now getting 1.44v

    good news is intel chips seem to be built like little tanks and can handle that spike.. I never seen the point of it because you can set the voltage higher and come pretty close to the same results.. some guys even hardcore oc'ers swear they can better more stable oc's though- and it's even put into the bios of some motherboards to disable it
     
  3. Fingers66

    Fingers66 Kiwi in London

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    Okay, so I should be okay reducing the vCore (to reduce overall load temps)? Is the fact that it increases under load a problem I need to address?

    My aim is the lowest vCore whilst stable under Prime95 to ensure lowest heat for my o/c.

    I understand about the 65nm being built like tanks, I am not too concerned about 1.4v under load, it is more the heat issue. I don't really want to run at 65C to 70C under load.

    I am using a Scythe Mini-Ninja with a Noctua 80mm fan, I might try an Arctic Freezer instead (I have one lying around) to see if that makes a difference.

    Thanks for the help.

    Fingers66
     
  4. thehippoz

    thehippoz New Member

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    ah thats too hot for e6600.. you should load under 60C.. you'll damage the chip for sure eventually under those temps

    you need a better sink or re-do the tims.. check intels chip spec http://processorfinder.intel.com/details.aspx?sSpec=SL9ZL

    stay within those limits if you want longevity.. you can go higher on the voltage if you have decent cooling- right now you need to get the load temps down.. I wouldn't consider prime on small fft a real world load temperature though (maybe blend)- try encoding and running games see what you average

    edit- oh the voltage will rise with the mod if you have too much pencil.. you should have just enough on to keep the vdroop the same as load
     
    Last edited: 30 Apr 2010
  5. Fingers66

    Fingers66 Kiwi in London

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    Thanks.

    I'll put the Freezer 7 Pro on tonight and give it a whirl. I will then drop the vCore down and try the blend test.

    Thinking about it, it has to be the CPU cooler as removing the side of the case doesn't make a difference (meaning enough air getting into the case) and the GPU (ATI 4870) only goes up to about 68C under load - the GPU fan doesn't go above 31%.

    I have also added a H/S onto the S/B and reseated the N/B with good thermal paste (the Asus stuff is crap) as they are renowned for running hot on this m/b.

    Cheers,

    Fingers66
     
  6. Fingers66

    Fingers66 Kiwi in London

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    Okay, heres the gist...

    First I got my cooling sorted (Freezer 7 Pro & different 120mm extraction fan), then removed the "pencil mod", just to be on the safe side. After reading Intel's stuff, the vdrop is by design so I thought I had better leave it as it is. My theory is that the pencil mod is used as a last resort in the quest for speed :).

    Anyway, after a bit of fiddling with vCore and n/b settings, here are the results:

    E6600 65nm @ 3.2GHz
    vCore @ 1.425v in BIOS
    n/b @ 1.563 in BIOS (Everest shows lower)
    RAM @ 800MHz (stock speed)
    Memtest fine

    Idle
    CPU = 46C
    Core 1 = 31C
    Core 2 = 31C
    m/b = 39C
    vCore = 1.42v

    Small FFT after a couple of hours
    CPU = 57C
    Core 1 = 55C
    Core 2 = 55C
    m/b = 39C
    vCore = 1.34v

    Blend after three hours
    CPU = 56C
    Core 1 = 52C
    Core 2 = 51C
    m/b = 39C
    vCore = 1.34v - 1.36v (goes up and down every few minutes)

    So all in all I am happy, good temps, stable and a 34% overclock! If I get time then I might leave Prime95 running for longer but I am confident that it is now stable.

    Thanks heaps for the pointer on the pencil mod, it prompted me to do some more homework first.

    +1 for the assistance thehippoz, much appreciated.

    Cheers,

    Fingers66
     
  7. Pete J

    Pete J RIP Teelzebub

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    Just to set your mind at ease, on my motherboard you have a choice of 'inverting' the vDroop so voltage increases under load.
     
  8. Fingers66

    Fingers66 Kiwi in London

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    Unfortunately my m/b only has limited o/c options. it is a good and fast m/b but they skimped on the quality of the power components IMHO.

    However, it will do me for now, I can't justify the cost of an i5 or i7 (+ m/b + RAM), especially now that the new sockets will be coming out next year. If the o/c I have can last me till then without killing the CPU or m/b then I will be happy.

    With the o/c and the 4870 (o/c'd as well) it can handle anything I can throw at it at the moment, there doesn't seem to be anything on the horizon that would change that significantly.

    Fingers66
     

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