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Test Details and Overclocking

Overclocking Core 2 Duo: Power Versus Performance
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The trick is to maximize performance while keeping power requirements within reasonable limits. Overclocking to as much as 4.2 GHz is possible, but this will require increased processor voltage, which has a noticeable negative effect on system power consumption. We found the ideal clock speed to be below 4 GHz (consistant with our findings when we ran Intel's Core i7 through a similar test in our story Overclocking Core i7: Power Versus Performance).

Since the board runs DDR3 memory, we wanted to be sure that the memory speed was not above DDR3-1333 at any time. This is because DDR3 memory is only affordable if you go for DDR3-1066—which you can typically overclock to DDR3-1333 with ease—or go straight for DDR3-1333.

Default: 3.33 GHz

A 3.33 GHz clock speed is the default for an Intel Core 2 Duo E8600. At this speed we had DDR3-1333 memory speed.

We increased the bus speed from 333 MHz to 360 MHz, which resulted in FSB1440 and 3.6 GHz core clock speed. No voltage increase was required, but the memory speed had to be readjusted to stay at reasonable levels. In this case the memory speed was DDR3-1152.

The second overclocking step was 3.9 GHz, based on FSB1560 speed or 390 MHz base speed. Memory speed went up a bit to DDR3-1248, which is close to the DDR3-1333 maximum we defined.


A 4.26 GHz core clock speed was possible at FSB1700, but only after a slight voltage increase of +0.15 V. In this case, the memory speed reached DDR3-1280.

Let’s look at performance and efficiency results to determine the best setting.

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  • -2 Hide
    SpadeM , June 6, 2009 6:43 AM
    Please fix the article, it's full of:
    Quote:

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  • 1 Hide
    anamaniac , June 6, 2009 7:36 AM
    Nice to see the C2Ds aren't forgotten.

    Personally it seems like I'm going from Pentium D to i7/i5 though.

    The C2Ds are cheap, reliable, fast. Not everyone needs 4 cores. A C2D is possible for a backup rig for me in the future.

    nice to see something I was going bogus trying to get 6 months ago is considered a backup option to me now... damn i7 and your awesomeness.
  • 6 Hide
    doomtomb , June 6, 2009 8:33 AM
    I still got my E6600 lying around. It was a great little processor. Dual-cores are highly efficient, most tasks can be completed on two cores and they overclock well.
  • -1 Hide
    Anonymous , June 6, 2009 9:30 AM
    Wow, that's the worst E8600 E0 I've ever seen !
    Even my very average E8400 at 4400mhz need less voltage than your E8600 @ 4.26ghz... I'm also stable at 4ghz with 1.28V .
    I've seen stable E8600 E0 @ 4300mhz with 1.325v.

    So I would like to warn overclockers that they are likely to get far more better results that Tom's in this article.

  • 2 Hide
    JeanLuc , June 6, 2009 9:53 AM
    gouroulubrikWow, that's the worst E8600 E0 I've ever seen !Even my very average E8400 at 4400mhz need less voltage than your E8600 @ 4.26ghz... I'm also stable at 4ghz with 1.28V .I've seen stable E8600 E0 @ 4300mhz with 1.325v. So I would like to warn overclockers that they are likely to get far more better results that Tom's in this article.


    I don't know about the worst I've ever seen but the choice of motherboard is........interesting. I that because according to CustomPC the best P45 overclocking motherboard is the Biostar i45.

    Still 4.26Ghz is a good return on what appears to be motherboard priced at the lower of the p45 range. However I don't understand what you beef is with MSI inculding PS2 connections for keyboards and mice, have you guys ever tried to run a text based version of Linux on a USB keyboard only to discover that it doesn't work? PS2 components still have their uses.
  • 0 Hide
    inmytaxi , June 6, 2009 10:07 AM
    Wow, that's a poor overclock.

    I reached 4.4 GHz (9 x 489 fsb) with a e8400 EO on air -- didn't try to go higher as the temps and voltages reached close to 70C under load/1.4 V idle (v goes down a little under load).

    I now have my e8400 E0 at 4.5 GHz (9 x 500) on cheap water (tt bigwater 735 refurb fifty bucks at their site), and plan to try to take it higher as temps are still ~66C. (29/39 C idle on core 0/1).

    I use the auto voltage setting on my Gigabyte GA P45 UD3LR(?), which sets it at 1.4 on boot, 1.392 idle and 1.36x load.
  • 0 Hide
    inmytaxi , June 6, 2009 10:08 AM
    btw my Gigabyte was 104 minus 20 rebate at MC, so that's pretty cheap too.
  • 1 Hide
    eddieroolz , June 6, 2009 10:30 AM
    For guys talking about the poor overclock:

    Remember, boosting your volts to 1.4v to get 4.4GHz is fine, but the article is about efficiency - not outright overclock.
  • -1 Hide
    gouroulubrik , June 6, 2009 11:22 AM
    Remember that power usage of an overclocked cpu is linear with the frequency, and ² with the fréquency !

    with the power supply calculator, you'll find out that a E8600 :
    4000mhz w/ 1.42v = 109w
    4400mhz w/ 1.35v = 109w !!
    It's all about this bad CPU that need way more voltage than usuals CPUs to get a descent frequency !

  • -1 Hide
    chovav , June 6, 2009 2:20 PM
    So it seems, like your core i7 overclock/efficiency comparison, that users should overclock their processors without turning the voltage up for highest efficiency.

    One thing to remember though, is that some motherboards increase voltage automatically when overclocking, which could result in different figures than shown here.

    Nice article!
  • 0 Hide
    Caffeinecarl , June 6, 2009 2:27 PM
    Very good article indeed! My Core2 Duo E8400 has made it up to roughly 3.8 GHz on stock voltage and 3.9 GHz after bumping it up to 1.2875v using just an Intel air cooler. For what it's worth, I didn't use the paper thin all aluminum stock cooler. I have a Pentium D that was laying around doing nothing after I bought the Core2 and the cooler had a copper core, so I used that instead. Better than the stock cooler, but definitely not the best. If anybody has a recommendation for a good quality, semi-affordable air cooler, drop a message.
  • 1 Hide
    Caffeinecarl , June 6, 2009 2:29 PM
    chovavSo it seems, like your core i7 overclock/efficiency comparison, that users should overclock their processors without turning the voltage up for highest efficiency. One thing to remember though, is that some motherboards increase voltage automatically when overclocking, which could result in different figures than shown here.Nice article!

    Some you can go automatic, or you can specify a voltage. Mine can go either way, but the automatic option I've heard in general is a definite NO. It builds up heat way too quickly to the point even small overclocks are a pain in the ass.
  • 1 Hide
    h83 , June 6, 2009 2:42 PM

    CaffeineCarl i can recommend you the Artic Cooling Freezer 7 Pro.
    It cost me 20 euros (in Portugal) and enabled me to push my E6400 from 2.13Ghz to 3.5Ghz with 1.55v.
    It´s easy to mount (just like the stock coolers from Intel), silent and does a very good job.

    Nice article, nice to see that the Core2 is still rocking!
    Hoping to upgrad soon to an E8400/8500 or Q9400/9550
  • 0 Hide
    h83 , June 6, 2009 3:41 PM

    By the way, does anyone knows if and when are intel to slash the prices of the Core2duo/quads???

    Any information would be apreciated!!!

    Thanks.
  • 0 Hide
    Oakley707 , June 6, 2009 4:06 PM
    Maybe it's just me, but I don't see exactly what voltage you were running when @ 4.26 Ghz. I apologize in advance if I missed it in the graphs or in the article.

    Just curious.
  • -3 Hide
    brendano257 , June 6, 2009 4:11 PM
    Oh quit whinning about how much voltage it takes you with your E0's. Try using a C0 E8400...takes about 1.4 to get to 4.05 Ghz. And why would you "warn" readers that they would see better performance. It's not dangerous or anything.
  • 1 Hide
    Anonymous , June 6, 2009 4:44 PM
    It would be a nice setting to give your CPU the slight boost it needs to get a few bit of higher framerates. But in most cases 3,33Ghz will be enough. In fact, in most games or programs, you might even benefit more from downclocking the processor, to a level just above being responsive enough not to cause too many delays (eg: don't let a menu appear,or action be done after longer than 10ms after the command was given), or that you still have fluid gameplay; but also downclocked far enough to save some $$$ in powersaving, and run the PC cooler.
    If a certain game runs fine with an 800Mhz processor, then why run it on 3Ghz? To get 150FPS? Instead run it on 1Ghz, and downclock the videocard too, as long as you won't see detail or quality reduced, that might be the thing to do.

    Electricity will start to cost more as soon as electric cars and vehicles become commercial. I believe we might see a time where standard light bulbs will no longer be sold (only energy saving ones), and rules will be set limiting TV's in power draw.
  • -1 Hide
    Anonymous , June 6, 2009 5:07 PM
    grreat write up, nice one toms :) 
  • -1 Hide
    chaohsiangchen , June 6, 2009 5:35 PM
    Which cooooler did you guys used in the test? 70W more total power consumption at load in 4.26GHz. That must be very good cooooooler. I'm interested in getting one of those.
  • 0 Hide
    ufo_warviper , June 6, 2009 7:15 PM
    While not, the fastest processors anymore, these seem to give you a decent percentage actual performance boost on most benchmarks when overclocked to 3.9 or 4.26 GHz. The Crysis results were unimpressive, but that was to be expected since Crysis is more of a GPU hog.
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