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: 14x (Stock 11x)
CPU voltage: 1.5875V
FSB Voltage: 1.30V
Memory Voltage: 2.20V
nForce SPP Voltage: 1.5V
nForce MCP Voltage: 1.7V
HT nForce SPP <-> MCP: Auto

Memory is set to Auto timings on the 680i and memory speed is linked to the FSB for the overclocking tests. This removes memory as any kind of impediment to the maximum stable overclock. Linked settings on the 680i are a 1066FSB to a DDR2 memory speed of DDR2-800. As FSB is raised the linked memory speed increases in proportion. The same processor is used in all cooling tests to ensure comparable results.

Highest Stable Overclock (MHz)

The Zalman 9500 reached just 3.812 GHz, which is middle of the pack and competitive with the much cheaper Thermalright MST-6775 and the Scythe Katana. The 9700 did a little better at 3.83 GHz. If you are just looking for bragging rights, then the 9700 booted fine at 3.90GHz, but unfortunately the system crashed whenever we tried to run any demanding tasks like gaming at any speeds above 3.83 GHz.

The overclocking performance of both Zalman coolers was disappointing. At $60 to $75 these are the two highest priced air coolers we have tested. You expect great performance if you pay more, but neither Zalman could deliver that kind of overclocking performance. Both the 9500 and 9700 were average in overclocking at best among the coolers we have tested. We can get average overclocking performance form coolers that cost just $25. Neither Zalman could justify their high prices based on overclocking performance, even though we tested both in overclocking at the highest fan speeds they could achieve, which also made them quite noisy.

The Tuniq Tower 120 is still the fastest air CPU cooler we have tested so far, with the TEC/air hybrid Monsoon II at the top of all overclocking charts with this CPU at 3.96 GHz. The Zalman 9500 and 9700 did not outperform the Tuniq, or even the Cooler Master Hyper 6+. Overclocking was in the ball park with the Thermalright and Scythe which are much lower cost and much lighter CPU coolers aimed at the heatpipe tower mainstream.

Cooling Results Noise
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  • Avalon - Monday, February 19, 2007 - link

    Keep up the good work. I'm enjoying watching the list of coolers you guys review grow and grow, and I think it's great that you'll be doing the Scythe Infinity and Ninja soon. I know I've mentioned this before, but I still want to see the Coolermaster Hyper TX if you guys can get your hands on one. Reason being is it looks as though it provides excellent PWM area cooling...which brings me to my next question...

    Have you guys considered throwing in PWM area temperatures? Some coolers are great at cooling the CPU, but awful at providing air anywhere else...and PWM cooling can help with stability.
  • Wesley Fink - Monday, February 19, 2007 - link

    We agree that PWM is an important consideration, and it is something we will likely visit in a future article. Most of the top motherboards these days use passive sinks on the power transisitors and northbridges, but they also come with cooling fans for use with water cooling and HSFs that do not provide good cooling for board components. The 680i has such a fan and we use it in our testing to try to remove the variable PWM air flow and temps as a performance factor. Of course, that avoids the question by removing the variable, rather than answering it. We will try to address this in some future article, but for now we have a lot more coolers waiting for tests on our standard test bed.

  • acivick - Monday, February 19, 2007 - link

    I didn't see it listed anywhere in the review, but I'm assuming that the included thermal compound was used, at least for the 9500/9700. If the same compound was not used for all coolers, they should be retested, as it's not a valid test. Using the same compound on each would make it more of an even playing field and would thus be testing the performance of the cooler only.

    For instance, MX-1 is supposed to be much better than the stuff Zalman provided, giving a 3-5C decrease in overall temperatures.
  • Wesley Fink - Monday, February 19, 2007 - link

    We use the thermal compound that comes with the cooler in most cases. If it is just a little packet of cheap thermal compound we use our standard, which is a silver colored tube thermal compound of pretty decent performance - not something exotic like MX-1.

    In the case of the Zalman 9500 and 9700 we used the Zalman Thermal Grease. Before replying to this question I tested the Tuniq Tower 120 with the Zalman Thermal Grease. Results were all but identical to the tests we ran using our bulk silver colored compound.

    Over the years I've used many thermal compounds, and if you use a quality product and apply it properly the results have been similar. I hear what you are saying about a 3-5C difference with MX-1, but I certainly have not seen those kinds of gains with any thermal grease. I can also point you to a serious review that shows toothpaste and Vegemite with superior performance to Arctic Silver 5. At some point in the future we might take a closer look at the impact of thermal compounds on performance, but for now I am confident our current test methods are not introducing new variables with sloppy choices of thermal compound. We are prudent in our choices, but not maniacal.
  • JarredWalton - Monday, February 19, 2007 - link

    Except a lot of people use whatever comes with the HSF. Wes would have to explain what thermal compound he's using, but I would assume he's sticking with the included stuff for each HSF where possible. If nothing is included... well, I don't know what he does there. :) Basically, though, I don't think retesting is in order unless he's using high-grade stuff on HSFs that omit the inclusion of a compound.
  • VooDooAddict - Monday, February 19, 2007 - link

    I agree that he should make it clear though what he's using.

    Using the shipped compound with these units would be preferable from complete product a review standpoint. As it stands there's no mention of his cleaning and reapplying new compound either. From a simplicity standpoint of reviewing and a better comparison of coolers, it would be easier to just use one compound for all the coolers to reduce cleaning time and variables.
  • ozzimark - Monday, February 19, 2007 - link

    umm, my 9500 looks NOTHING like that base :-X

    http://www.eclipseoc.com/image/cooling/zalman%20cn...">click for pic!
  • dev0lution - Monday, February 19, 2007 - link

    Good info. I was leaning towards getting the 9500 since I don't think my 7700-alCu will fit on the eVga 680i board I haven't got around to installing. I might consider getting one of the alternatives now, seeing as how it doesn't look like the zalman's are worth the price premium.
  • Fishie - Monday, February 19, 2007 - link

    quote:

    Neither Zalman was particularly quiet, and the 9700 was one of the noisiest coolers we have tested in the lab at 2800 RPM - twice the noise of the Tuniq Tower 120 at high speed and almost as loud as the Monsoon II Lite which is plagued by buzzing and clicks from fan switching.


    The Tuniq is 54dBs while the 9700 is 57dBs. Twice as loud? Wouldn't twice as loud be 108dBs? Not to mention the 9700 is quieter than the Tuniq at 24" away.
  • Wesley Fink - Monday, February 19, 2007 - link

    3db is twice the sound energy, since the db scale is logarithmic. At one time twice the energy was considered twice as loud, but recent research shows 6db to 10db increase to be perceived by the human ear as twice as loud - depending on whose study you read. I have stated this in past reviews. To be more precise I changed the wording in the review to twice the sound energy.

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