Overclocking

As cooling solutions do a better job of keeping the CPU at a lower temperature, then it is reasonable to expect the overclocking capabilities of the CPU will increase. In each test of a cooler we measure the highest stable overclock of a standard X6800 processor under the following conditions:

CPU Multiplier: 11x (Stock 11x)
CPU Strap: 266 or 333
CPU voltage: 1.5875V at Max overclock
FSB Voltage: 1.40V

Memory is set to Auto timings on the P35. This removes memory as any kind of impediment to the maximum stable overclock. As FSB is raised the linked memory speed increases in proportion. For this reason memory speed is maintained as close as possible to CPU strap settings to prevent memory becoming an issue in CPU testing. This means 3.33GHz uses a 333 strap and runs 10x333, 3.73GHz runs a 333 strap and runs 11x339, and 3.90GHz is 333 strap and 354x11. The stock speed test is 266 strap and 11x266. We may move in the future to a 3.0GHz stock speed with a 333 strap and 9x333 settings for complete consistency, but since we are not measuring raw computer performance in our cooling benchmarking this becomes a moot point. The same processor is used in all cooling tests to ensure comparable results.

Highest Stable Overclock (MHz)

The OCZ Vendetta tops out at 3870MHz - near the top of tested air coolers. This matches the Thermalright Ultima-90 when it is running a 90mm fan, but it does not quite reach the 3.90 to 3.94GHz of the top coolers tested. However, for around $30 the OCZ Vendetta is able to match the best overclock that could be achieved with entry level water cooling with the Corsair Nautilus 500 or the Swiftech H2O 120 Compact. That is pretty impressive performance for a cooler aimed at midrange air. To be fair the operating temperatures across the speed range for the OCZ Vendetta are generally not as good as the water cooling kits, but the temps are still in the safe range for the X6800 CPU.

The Scythe Kama Cross is more like an Intel retail cooler on steroids (admittedly a light dose), reaching 3.80GHz with the stock 100mm fan and 3.83GHz with the 120mm fan. With the starting price of the Kama Cross actually being higher than the Vendetta, it is difficult to get excited about these overclocking results.

As stated many times, the overclocking abilities of the CPU will vary at the top, depending on the CPU. This particular CPU does higher FSB speeds than any X6800 we have tested, but the 3.90GHz top speed with the Thermalright Ultima-90 with 120mm fan is pretty average among the X6800 processors we have tested. A few of the other processors tested with the best air coolers reach just over 4GHz, but the range has been 3.8 to 4.0GHz. Stock cooling generally tops out 200 to 400 MHz lower, depending on the CPU, on the processors tested in our lab.

Scaling of Cooling Performance Final Words
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  • rbuffetta - Tuesday, October 2, 2007 - link

    Spend the extra $20-30 and get the Thermalright Ultra 120 Extreme. Of all the places to cut corners and save money this is really where it counts to protect your cpu and allow for decent overclocks.
  • EtherealDragon - Tuesday, October 2, 2007 - link

    As always, it was a nice read, but why oh why would you plot the 2 graphs on page 7 in that manner? Seems funny to me to have the points on the graphs "drop" as the temperature raises... I guess thats just my .02
  • Wesley Fink - Tuesday, October 2, 2007 - link

    It's very easy to change the chart with temp going up if enough readers prefer it. We changed the graph scale after receiving several complaints that the top performance was the lowest chart position on the old charts and difficult to comprehend. If more readers prefer the original chart layout we will be happy to change back. Please let us know.
  • strikeback03 - Tuesday, October 2, 2007 - link

    I prefer the old orientation, as it makes sense to me that when you are looking for the cooler with the lowest temperature, you look at the lowest point on the graph.
  • Sentrosi2121 - Tuesday, October 2, 2007 - link

    Pretty acceptable for the OCZ cooler. I wonder how it would perform inside an enclosure like the X-Qpack. I'm trying to build a nice gaming rig with the X-Qpack and would like to see if it would fit inside.
  • Basilisk - Tuesday, October 2, 2007 - link

    quote:

    I wonder how it would perform inside an enclosure like the X-Qpack.

    Depends on your skill with a hammer and chisel: The X-Qpack (and X-Qpack2 and Ultra Micro Fly) only have about 75mm of headroom above the CPU -- challenging for a 92mm fam mounted perhaps 40mm above the CPU! Go with a Zalman horizontal flower (7000, 7700, 8700), a few other units or just the stock fan in those cases.

    PS: The X-Qpack2 has improved airflow and clearance (length) over the X-Qpack.
  • Anonymous Freak - Tuesday, October 2, 2007 - link

    StorageReview just did a review of the http://www.storagereview.com/1000.sr">Western Digital "Green Power" 1 TB hard drive. While it's not the best performing drive in the world, it's no slouch, and it has the side effect of being the quietest drive they've ever tested. (Plus it runs cool enough that you could probably slap it in a
  • EtherealDragon - Tuesday, October 2, 2007 - link

    As always, it was a nice read, but why oh why would you plot the 2 graphs on page 7 in that manner? Seems funny to me to have the points on the graphs "drop" as the temperature raises... I guess thats just my .02
  • Phil Harris - Monday, October 1, 2007 - link

    It seems utterly ridiculous to me that these coolers are tested on dual setups.
    If someone looking to build a quad is trying to find useful information, this review is completely pointless.

    A test on a quad however will still provide useful info to someone building a dual core.

    The defence that games don't use quads yet is also totally specious, if thats the reason, why bother testing anything other than dual core machines?

    Lets all ignore quad core computing until we can play games on them... is that the idea?

    This is the second poor quality review in the cases and cooling section within a few weeks, if Anandtech wants to be taken seriously, a serious re-think is required.
  • Acanthus - Monday, October 1, 2007 - link

    Many enthusiasts that are spending money on components for overclocking have opted for cheap quad cores.

    Sorry to sound frustrated, but this is getting rediculous when we are in the world of $270 quad cores.

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