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Lower your load temps: minimize your vcore

Discussion in 'Overclocking & Cooling' started by graysky, Jun 14, 2007.

  1. graysky

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    Sounds pretty simple, but you'd be surprised how many people don't know about how much vcore can affect your load temps. Temp and frequency (FSB) have a linear relationship whereas temp and voltage have an exponential relationship. Conclusion: minimize voltage.

    Here is the Intel document that helps explain it, see page 31:

    Same thing holds true for speed in a car: energy = 0.5mv^2 where m is mass and v is velocity. This is the basis of the old expression, "speed kills." You generate way more energy driving 75 MPH than you do driving 55 MPH since energy and velocity have an exponential relationship.

    Anyway, to test how low you can go, simply manually set your vcore for something low. I started @ 1.2375 for my Q6600 running @ 9x333. If you can boot into windows load up a couple instances of orthos. If you have a quad make sure you set the CPU affinity such that one of the orthos gets cores 0 and 1 and the other gets cores 2 and 3. Let em run for a while. If the vcore is too low, one or both will give an error message. Orthos checks e when for rounding errors that can occur when the system isn't stable due to vcore, or temp, etc. Using a vcore of 1.2375v for my system gave an error pretty quickly:

    [​IMG]

    If you don't get an error after say, 30 min, lower the vcore in the BIOS and repeat until you do get an error, then start working your way up until you can run them with no errors for a good 6-8 hours. In a nutshell, that's it.

    Enjoy.

    Here are the results from a little experiment I just finished wherein I ran p95v2 with 4 threads doing large FFTs for ~1 h on a Q6600 @ 9x266 under two different vcores: 1.2625V in BIOS or 1.232V in CPU-Z and 1.1125V in BIOS or 1.080V in CPU-Z. I had the logging disabled so these aren't average temps, just "instant" temps although I they really did level out.

    Results @ 1.232V:
    Code:
    Core0=55
    Core1=56
    Core2=51
    Core3=52
    Results @ 1.080V:
    Code:
    Core0=49 (6 °C cooler)
    Core1=50 (6 °C cooler)
    Core2=48 (3 °C cooler)
    Core3=48 (4 °C cooler)
    Result: 152mV in vcore can make a pretty big difference in temps. Oh, room temp for this was 75-76 °F throughout.
     
  2. [I.R.A]_FBi

    [I.R.A]_FBi New Member

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    hmm ...
     
  3. infrared New Member

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    I didn't think something like this needed a guide, but still a good write up.

    BTW, it's the small FFT's you need to use to stress the cpu the most with p95/orthos ;)
     
  4. anticlutch

    anticlutch New Member

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    Wow.. Core 2 Duo's are insane. They overclock insanely high and handle undervolting very well too... I'm stress testing my E6400 at 1.000 vcore +stock speeds and it's pretty solid. A few more minutes of Orthos and I'm going to try for even lower :p

    edit: Seems like anything under .95vcore won't work... oh well :D
     
    Last edited: Jun 14, 2007
  5. graysky

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    Just be sure you use the Intel processor finder to see what the vcore range for you chip is and be sure you don't undervolt below that range. Also, those numbers are AFTER any vdroop your board may have so be sure to read it in the BIOS or CPU-Z. My Q6600 for example can run stable @ 1.1000V which is like 1.064V after the vdroop which isn't safe since it's below the min. Intel recommends.
     
  6. WarEagleAU

    WarEagleAU Bird of Prey

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    Im assuming this is only for Intel Chips and C2D designs?
     
  7. infrared New Member

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    no, any cpu can be undervolted to reduce temps ;)
     
  8. anticlutch

    anticlutch New Member

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    Well it says mine is good down to .85 vcore so I'm safe (drops down to somewhere around .93v after vdroop)... useful website though :D
     
  9. HellasVagabond New Member

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    Isnt this 101 of the Overclockers book ? :p
     
  10. Zeratul_uy

    Zeratul_uy New Member

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    At least he did a simple post about it :rolleyes:

    I don't see you contributing to something with that question...


    Nice Graysky, it would help some noobs in the matter (including me :rockout:)
     
  11. Dippyskoodlez

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    I had always found temperature scaling Vs Speed, and voltage were really interesting with CPU's.

    [​IMG]

    Thats a real rough diagram I made a long time ago when experamenting with raw Athlon XP calculations (purely theoretical).

    By adding ~50% voltage, you have gained almost 100% in power used. Whereas +50% freq gives you a 50% power increase. Up the voltage, and you instead get a >50% power increase with the exact same CPU speed.
     
    Last edited: Jun 16, 2007
  12. Casheti

    Casheti New Member

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    This will be useful in a million years when I upgrade to a mobo than can overclock lol...

    Nice guide :)
     
  13. HellasVagabond New Member

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    Its not even a guide...Its simple logic that i believe all of us have....
    Hey whatever works for you i guess :)
     
  14. Zeratul_uy

    Zeratul_uy New Member

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    hum, yes, ok whatever you say :D
     
  15. Dippyskoodlez

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    This is a DUH for people that understand the mechanics of overclocking...

    to some it maybe isn't terribly obvious..
     
  16. Kursah

    Kursah

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    I wouldn't even go that far, but it's an idea to create a less restrictive airflow path for more efficient cooling. I did that on my 120mm exhuast hole on my current case, I did it the lame way with snips and left the rough edges, but applied some electrical tape around them, that also helped to dampen reverberation noise from the fan itself. Cheap and easy!

    If this were to be considered a guide, it should have pictures of before, during, after steps, and proper precautions and warnings when working with metal, sharp objects, and electronic saftety precautions. But it's a nice thread, it never hurts to have pictures to show what people mean sometimes.
     
  17. Dippyskoodlez

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    Wrong thread. :roll:
     
  18. tkpenalty New Member

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    He means better cooling > undervolting :roll:
     
  19. HellasVagabond New Member

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    Thats what i gathered....I guess it was supposed to get into the other thread...How did it end up here ? :p
    ( Fans , exaust holes , Cutting....Yeap its about the other thread. )
     
  20. Dippyskoodlez

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  21. Kursah

    Kursah

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    Yep I did...lol

    Sorry, I had mult windows open and got in the mode! LoL! How about that for a blonde moment! Well, at least my beer isn't laughing at me!
     
  22. nflesher87

    nflesher87 Staff

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    well I've gotta say I really appreciated this thread lol I've never gotten the chance to OC yet as I haven't had access to a comp that's capable! so I haven't done a whole lot of research into it yet but this is a very basic principal that I won't forget!
    so thanks bro :toast:
     
  23. devguy

    devguy

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    You could just do what I do. Overclock the beast with higher than standard vcore in the bios, and then in RMClock, set the vcore for the lowest multiplier possible to the lowest stable amount. Then just have it run at the lower multiplier until cpu load > 75% or so, in which case it will change to the full multiplier. Works great for power saving and for low temperatures on A64 machines as well as my Pentium M (probably any other mobile Core architecture processors as well). My Idle temperature for my A64 is just slightly above 100F and this is in an matx case mind you. My laptop idle temperature is just under 100F after the undervolting and some Arctic Silver 5 application.
     
  24. graysky

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    Here is a more detailed analysis of two difference vcore settings and the temps they produce on a Q6600 @ 9x266=2.4 GHz as well as @ 9x333=3.0 GHz. The two voltages I used were 1.112 V and 1.232 V (both of these are the load voltage, the actual BIOS settings were 1.1375V and 1.2625V respectively).

    2x orthos ran for 30 minutes and the temperatures were averaged over the last 10 minutes of those runs (well after they stabilized). Room temps was 75-76 °F. Notice that the difference in voltage is ONLY 0.120 V or 120 mV, but this seemingly small difference brought the load temps up by an average of 6-7 °C per core!

    Code:
    Run1 (9x266 @ 1.112 V), Average temps (°C): 51,52,50,50
    Run2 (9x266 @ 1.232 V), Average temps (°C): 57,58,57,57
    Differences (°C): +6, +6, +7, +7
    Now if I add a faster FSB, they increased further:

    Code:
    Run3 (9x333 @ 1.232 V), Average temps (°C): 61,61,60,60
    Differences from lowest voltage (°C): +10, +9, +10, +10
    Differences from same voltage (°C): +4, +3, +3, +3
     
    Atech says thanks.
  25. hat

    hat Maximum Overclocker

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    Someone did a tutorial on this before with an Opteron. I beleive he got to .9 volts or something stable on stock clocks.
     
    Crunching for Team TPU

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