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Multiplier Overclocking With Turbo Boost

Core i7-980X: Dialing In Efficiency With The Right Overclock
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The simplest approach to overclocking is simply increasing the clock ratio. The system uses this to generate the CPU clock speed as a multiple of the base clock frequency (set to 133 MHz on all Nehalem-based platforms). For example, 133 MHz times a 22x multiplier results in 2,933 MHz, or 2.93 GHz. Modern systems employ various multiplier settings to decrease both clock speed and power consumption (a la AMD Cool’n’Quiet technology or Intel Enhanced SpeedStep), while technologies such as AMD's Turbo CORE and Intel's Turbo Boost apply higher multipliers to achieve faster performance (more on Turbo Core in the days to come).

Unfortunately, there's a catch to increasing the multiplier. Processor manufacturers generally limit maximum ratio settings to ensure that a processor will not run faster than specified. The remaining option is typically to increase the base clock, which also results in a higher effective CPU speed. However, this can put system stability at risk because related components, like the chipset and system memory, are also overclocked.

Multiplier-based overclocking is clearly superior, and both AMD and Intel know this. The two companies use unlocked multipliers as a value-add on their flagship offerings to draw in the enthusiasts willing to pay a little extra for the added flexibility. Of course, AMD labels its unlocked parts as Black Edition, while Intel labels its highest-end CPUs Extreme Edition components.

Needless to say, AMD's CPUs have remained relatively affordable, while one might think the Extreme family was named for its $1,000 price points. The Core i7-980X is an Extreme Edition chip in the truest sense of the word, with unlocked multipliers and mad overclocking potential. But features like Turbo Boost factored into the CPU's overclocking potential requires a harder look at the possibilities here.

Overclocking on Turbo Boost

Turbo Boost makes overclocking a bit more complex, since the feature can increase a processor’s clock speed by one or several ratio settings when under load (each "bin" being a 133 MHz increment). To make things more interesting, Turbo Boost has different effects, depending on the number of threads involved.

Certain Core i7 processors designed for the LGA 1156 interface can accelerate one core by as many as five speed increments, two cores by up to four increments, and three or four cores by one or two increments. All of this depends on the processor model, though.

In the case of Core i7-980X, Turbo Boost is limited to two speed bins if one core is taxed, or two speed increments for two or more cores. Given the higher Turbo Boost speeds found in the mainstream models, though, this seems disappointingly modest. Luckily, you can modify the Turbo Boost settings in the BIOS, so long as you're using a motherboard with the needed settings (see screenshot above).

Although it's possible to define the multiplier for one to six active cores separately, we decided to stay with Intel’s default settings and simply increase all multipliers by one for each overclocking step we made. You will find our individual settings in the overclocking table later in this article.

Settings, Voltage, And Power Issues

There are a several things to look at when overclocking. Depending on your motherboard model and BIOS, these may vary a bit. The following terms are taken from the Intel DX58SO we used for this article.

TDC Override: Thermal Design Current Override

Be sure you allow the processor to run higher currents when overclocking.

TDP Override: Thermal Design Power Override

You may recall that the Core i7-980X has a TDP of 130W. This won’t suffice once you start to overclock, especially if you’re also increasing voltage.

Static CPU Voltage Override

You can apply a fixed voltage to your CPU. This is often best for reaching top speeds, since dropping and increasing voltages (caused by SpeedStep) typically doesn’t contribute to system stability.

Dynamic CPU Voltage Offset

Here you can define a voltage increase to add to the default voltages. This is what we used to increase CPU voltage for our two highest overclocks.

Power Issues

Finally, we didn't apply overclocking settings that would require significant voltage increases. There's already plenty of computing power available at near-default levels, plus we found that increased voltage has much more impact on system power consumption than clock speed increases. Take a simple example: we found that the Core i7-980X is stable at 4.13 GHz (4.26/4.4 GHz in Turbo Boost) at +0.075V processor voltage. At this setting, we measured a peak power consumption of 322W. The same speed settings at +0.25V required over 400W. This is quite significant considering that system idle power almost always remains around an impressively low 85W.

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Top Comments
  • 12 Hide
    babybeluga , April 9, 2010 6:51 AM
    Not worth the time and money!


    ...yet
  • 10 Hide
    Sihastru , April 9, 2010 7:32 AM
    Looks like 32nm will be a gamechanger for Intel CPUs. What I'm missing though is temperature readings. It would be interesting to see how much higher they are when overclocking "efficiently".

    Still at ~$1000 a pop, most of us can just take this CPU as a hint of "things to come" and not really consider one for purchase any time soon.
Other Comments
  • 12 Hide
    babybeluga , April 9, 2010 6:51 AM
    Not worth the time and money!


    ...yet
  • 3 Hide
    dlochinski , April 9, 2010 7:11 AM
    What a beast
  • 0 Hide
    Lmeow , April 9, 2010 7:15 AM
    Just wondering, if Turbo Boost is enabled when you have overclocked your CPU, does TB add to your overclock? E.g., if you have an i7 900 @ 4Ghz, does it go to 4.133GHz w/TB?
  • 10 Hide
    Sihastru , April 9, 2010 7:32 AM
    Looks like 32nm will be a gamechanger for Intel CPUs. What I'm missing though is temperature readings. It would be interesting to see how much higher they are when overclocking "efficiently".

    Still at ~$1000 a pop, most of us can just take this CPU as a hint of "things to come" and not really consider one for purchase any time soon.
  • -2 Hide
    victomofreality , April 9, 2010 7:35 AM
    if cash wasn't an issue I would totally get one for bragging rights but not worth the cash.
  • -1 Hide
    jsowoc , April 9, 2010 7:38 AM
    After the intro mentioned the Core i5-670, I almost expected it to be part of the benchmark. With less cores, you should be able to push it further, and it might perform faster than the i7-980X on the single- or dual- core benchmarks. We need to know what (if any) is the difference between the $1000 beast and the $300 beauty.

    Is a Core i5-670 overclock article in the works?
  • -2 Hide
    evolve60 , April 9, 2010 8:01 AM
    http://www.juns.jp/980X.html

    They managed to get the 980X up to 5GHz with 1.688volts, but at that voltage the chip is bound to get fried sooner or later, but I just thought that this was worth mentioning seeing as how Toms emphasized on how Intel skimped out on the Turbo boost feature.
  • -6 Hide
    starralazn , April 9, 2010 8:38 AM
    LmeowJust wondering, if Turbo Boost is enabled when you have overclocked your CPU, does TB add to your overclock? E.g., if you have an i7 900 @ 4Ghz, does it go to 4.133GHz w/TB?

    you obviously have never overclocked a CPU with turbo boost.
    Once you reach a stable oc setting with turbo boost off, and try to turn it on, your setup probably won't make it past startup because that part will throttle up your CPU past the limit capable of your CPU
  • 1 Hide
    fusionlance , April 9, 2010 8:59 AM
    I so wanted this for Maya, 12 threads ought to cut 60% of the rendering time compared to the system I'm currently using.
  • 9 Hide
    Anonymous , April 9, 2010 9:41 AM
    Motherboard
    (Socket LGA 1156)

    I believe that is not right ;) 
  • 0 Hide
    Reynod , April 9, 2010 10:20 AM
    The tables were useful.

    I'd run one of these at 3.73 ... that seems the sweet spot and no worries about electromigration as long as you have a quality aftermarket cooler.

    Frying one od these would surely make the toughest overclocker weep real tears.

    Putting the stats in for an i5 and i7 reference cpu would also have been nice guys.

    Good work.
  • -2 Hide
    RazberyBandit , April 9, 2010 10:34 AM
    Aww. With those initial comments about an OC'd i5 potentially outperforming this thing in a single-threaded, I was hoping to actually see it happen.

    Very interesting how well it can OC at it's stock voltage, and how well it scales while doing so.
  • 1 Hide
    Anonymous , April 9, 2010 10:44 AM
    How did you test stability? Did you use Linpack? I ask because there is a significant difference between what is stable in Linpack and what is stable for example in orthos. My i5 750 runs orthos small fft test just fine at 4.1GHz for 12h and crashes in Linpack at that frequency after 5 minutes. I can only achieve 24h stability in Linpack at 3.77GHz. As for dual core i5, you have to take into account that dual core i5 do not have IMC, thus they have much lower performance per clock then "true" Nehalems.
  • -3 Hide
    anamaniac , April 9, 2010 10:50 AM
    Cool, using the reference cooler and keeping HT/Turbo on, nice.

    Now, how about a better motherboard, a high end liquid setup, and turn HT and Turbo Boost off (HT is useless unless you actually need it, which most of us don't).

    You know you wanna. :D 
    For the sake of all Tom's devotees... RUN THAT MOTHA TILL IT BURSTS IN FLAMES!
  • 3 Hide
    Luscious , April 9, 2010 11:58 AM
    Very nice article, but some folks with dough to buy a $1000 CPU to OC will be running high-end water or phase-change.

    Time to do a follow-up article and get a Swiftech h2o kit in your labs alongside a phase-change unit. You guys do, after all, want to see how far this processor can go, right?
  • -1 Hide
    Anonymous , April 9, 2010 12:28 PM
    Anyone know how this chip compares to the i7-920XM (Extreme Calpella Clarksfield Processor 2.0-3.2GHz)? I mean if Turbo Boost will get this ship to 3.2 and the Gulftown to 3.6... on single cores would the 920 be competitive?
  • -1 Hide
    flyhiloone , April 9, 2010 1:28 PM
    I really appreciated this article. Just last week I picked up one of these bad boys for my business (video editing) and have really noticed a difference in the amount of time it takes to process/edit my work. I can't wait to go home and try some of these overclock settings.
  • 0 Hide
    whiz , April 9, 2010 1:34 PM
    Damn i like how old-school intel MBs always look like - i bet the guy responsible for the cooling solutions is a 60yr. old guy who's been working at intel since they opened =)
  • 1 Hide
    Ogdin , April 9, 2010 1:54 PM
    Worrying about power efficiency with a $1000.00 cpu.........that makes a lot of sense lol.
  • -1 Hide
    Anonymous , April 9, 2010 2:53 PM
    Wow... 3.86 ghz..

    6 cores, 12 threads, HT on, TB one... all at stock voltage....

    I guess we can say that the 32 nano process is up and running, couple steppings and this thing will we deep into the 4 ghz range.

    Makes you wonder why Nehalem EX is still at 45 nano's. If ever their was a chip that cried of for all this 32 nano goodness that would be the one.
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