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Undervolting Your Phenom II And Core 2 Processors

Undervolting Your Phenom II And Core 2 Processors

Enthusiasts generally try staying up to date when it comes to overclocking processors. They spend a lot of time answering these sorts of questions: How fast can certain processors go? What voltage levels do you need to get there? And what’s the best cooling solution?

But while overclocking lets you bump CPU performance to the levels of more expensive processor models, it is also possible to go in the other direction. You can typically undervolt a processor in an effort to improve efficiency without affecting performance at all.

Voltage, Clock Speed, and Power Consumption

Clock speed is one of the biggest determinants of performance, and increasing voltage is typically an action taken to enable higher clock speeds. With that said, voltage plays the most important role in establishing power consumption, with clock speed playing a secondary role in that arena. Increasing or decreasing clock speeds has a straight proportional impact on power, while power actually scales with the square of voltage. For this reason, bumping up voltage always has a more significant impact on power consumption than a clock speed increase.

And of course, reducing the operating voltage can have a significant impact on power consumption, which is why we decided to look into it.

Lower Voltage Products

Many mobile processors are simply modified, low-voltage versions of common products. Think of Intel’s Core 2 mobile processors. These are power-optimized, but under comparable conditions, they would perform and consume power like their desktop brothers. The Core 2 Duo T-series is rated at a maximum power consumption of 35 W, the P-series stays within a 25 W envelope, and so forth.

But there are low-power parts for desktop systems as well. AMD offers energy efficient processors with the suffix “e” (Phenom II X4 900e, 905e, and the Phenom X4 9350e). Intel is offering Core 2 Quad “S” models, which deliver the same performance as the regular models, but within a 65 W thermal envelope instead of 95 W. Although the lower-power processors are too expensive, if you ask us, they don’t fail to impress, as both the idle and peak power of test systems decreases.

Low-Voltage CPU Do-It-Yourself?

So what if we were to tweak CPU voltage ourselves? If overclocking and overvolting have become so popular, it couldn’t hurt to try some undervolting. We setup two MSI motherboards that we had at our disposal: a P45D3 Neo, which we recently used to find the perfect Core 2 Duo overclock, but this time with a Core 2 Extreme QX9650, and a 790FX-GD70, allowing us to test AMD’s Phenom II X4 955.

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  • 0 Hide
    Anonymous , 15 July 2009 18:38
    Half-hearted article. If you 're serious about doing this (or you have a laptop) try RMClock.
  • 0 Hide
    sebanab , 15 July 2009 18:51
    Good article.
    harry123Half-hearted article.

    Since the topic is power saving it is understandable.

    One addition: for the readers not able to measure the power saving , you can check the CPU temperature with and without the voltage modification and you will see the difference.

    A second addition: a true power saver should also accept a slight performance drop. So lowering peak frequency is another option.
  • -1 Hide
    AMD4Life , 16 July 2009 01:43
    AMD finally managed to threaten Intel’s Core 2 Quad in some benchmarks, but at somewhat lower cost both for the processor and an average platform. However, the Core i7’s reign remains untouched.

    Actually, AMD beat the s**t out of C2Q and threatened I7 in some benchmarks. Get it right Tom. Darn I hate this site.
  • -1 Hide
    shrex , 16 July 2009 14:59
    Where did it beat the shit out of C2Q, performance per watt intel win.
  • 0 Hide
    Micropat , 17 July 2009 05:02
    Does anyone think there would be such margins for undervolting notebooks or would they be tuned a bit better than their desktop counterparts to maximize battery life anyway? Of course in most cases this is a hypothetical question since I believe that most notebooks don't allow alteration of processor voltages up or down.
  • 0 Hide
    kingnoobe , 17 July 2009 06:15
    Amd4life quit being a fanboi. You're not any cooler for being a hater either. Intel is beating the crap out of AMD performance wise it's just the way it is. Get over it..

    Amd is beating the crap out of intel pricing wise.. It's just the way it is....

    Fanbois only hurt themselves.. You miss out on so many good products because you think you're being loyal when in reality you're only being a retard!
  • 2 Hide
    Reynod , 17 July 2009 17:07
    AMDFangirl has been undervolting stuff and posting about it for 18 months ... and quite a few have been undervolting the 45nm Intel quads in the forums too.

  • 0 Hide
    butcher , 17 July 2009 23:10
    Why not have the best of both worlds

    I have OCed my I7 to 3.3Ghz while reducing the voltage to 1.1V (after vDroop)

    and my I7 is not that great, i have seen some that do the same OC with much less
  • 0 Hide
    Anonymous , 19 July 2009 08:39
    I had an Opteron 165 Dual Core 1.8ghz stock v1.35 ocd to 2.7ghz at v1.2 ! Incredible...
  • 0 Hide
    Anonymous , 26 July 2009 07:35
    AMD4Life, i would like to see some facts or benchmarkscores of that, the i7 remains untuched and the amd and intel duo is splitting haris performance wise

    The intel is more efficent but the amd is more secure for the future.

    The i5 will probably beat the heck outta the amd in performance at the same price and also being secure for the future.

    my 2 cents, split them either way.