Overclocking

As cooling solutions do a better job of keeping the CPU at a lower temperature, 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: 1.90V
nForce SPP Voltage: 1.35V
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 Thermalright Ultra 120 with the Scythe S-Flex fan matched the Tuniq Tower 120 at 3.90GHz. This is the highest stable overclock we have reached on air cooling with this CPU. While we could boot at speeds as high as 3.96GHz, gaming performance was not stable at speeds higher than 3.90GHz. Increasing the CPU voltage also did not increase stability above 3.90GHz.

The best coolers tested have topped out at 3.90GHz. This represents the highest stable overclock that has been achieved with this CPU with air cooling. While we will continue to try to push the better coolers even further than 3.90Ghz, it is fair to conclude that the maximum OC on air with this processor is likely 3.90GHz. The Vigor Monsoon II achieved a higher overclock, but only with Thermal Electric Cooling.

Scaling of Cooling Performance Noise
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  • Wesley Fink - Monday, March 5, 2007 - link

    The Thermalright mounting holes were not designed to hold fan wires for two fans. They are about the diameter of a single wire and two just won't fit. The lower fan clip mount hole opens and breaks if you try to mount two fan wires in the mounting hole. Clearly Thermalright did not design the Ultra 120 for multiple fan mount, though we agree the design looks a natural for a push-pull fan setup. In the end the Thermalright cooled as well or better than anything, even a two-fan Infinity, using just one excellent fan.

    The mounting surface of the Thermalright was reasonably flat and smooth. The flatness mattered a great deal more when you were dealing with a small surface area mount like the AMD Socket A from the past. With processors today shipping with a large area heatspreader the surface flatness is less important, but it still matters.

    The proper application of thermal compound matters a great deal in performance. We usually place a little larger than a BB-sixed glob of thermal in the center of the CPU and mount. When the heatsink is removed that normally has spread on mounting to the edges of the processor with no thermal grease builup around the sides of the processor. THe prurpose of thermal grease is to fill the irregularites of the mounting surfaces and improve contact between the mounting surfaces.
  • xsilver - Monday, March 5, 2007 - link

    would it be easy for a mod job to add the ability to mount 2 fans? screwing them in to the fins directly maybe?
  • JoKeRr - Monday, March 5, 2007 - link

    Guess in the end it's not just the # of heatpipes and overall fin surface area. Great review overall. btw, what kind of thermal compound do you guys use? And I thought fluid dynamic bearing was developed by Panasonic instead of sony.

    Would it be possible in the future to test arctic coolings Freezer 7 Pro? That looks like a decent tower heatsink, and it comes with a fan too. Also it's much cheaper as well. It will be really nice to see how that heatsink compares to the bigger towers. Another question I have concerns with previous generation heatsinks. Currently I have a ThermalRight XP-90 with a 92mm panaflo, my cpu is a socket 478 P4 3.0ghz OCed to 3.6ghz at default v-core (it's a northwood core btw). I know XP-90 is a very good heatsink, and I'm really considering of using it on my future LGA775 setup (with a LGA775 bracket), but it's really hard to compare it with new heatsinks. Thanks again.
  • Wesley Fink - Monday, March 5, 2007 - link

    I have referenced the review showing toothpaste and Kraft Vegemite superior to a well-known siver compound several times in past review comments. As we have stated several times, in our experience the thermal compound doen't matter. The Thermalright comes with a white soupy themermal compound in a tube, and that is what we used. As we have said before, if the cooler manufacturer cares enough to include a tube or jar of thermal grease that is what we use. If it is just a packet or no thermal grease included, we use our standard silver-colred (no silver content) tube thermal compound.

    In our tests of various thermal compounds in the past, we found the thermal compound made used made no difference at all. That is particularly true now that all the current CPUs use heatspreaders. On past small surface area processors like the AMD Socket A, The thinner compounds were sometimes more effective short term, but even there the thermal grease used made no difference in cooling after a few days pf seating - all else being the same.
  • Souka - Monday, March 5, 2007 - link

    Hmm...

    I seem to recall a number of reviews that clearly demonstrate the differing effects of compounds on coolers....

  • DrMrLordX - Tuesday, March 6, 2007 - link

    I believe you mean reviews like this?

    http://forumz.tomshardware.com/hardware/DaClan-Rev...">http://forumz.tomshardware.com/hardware...-Interfa...

    Shin-Etsu x23 = winnar
  • goinginstyle - Monday, March 5, 2007 - link

    What were the results of this fan in the Tuniq 120 and did you try it on the Scythe that was reviewed last week? It looks like a fan review is in order after seeing these results.
  • Wesley Fink - Monday, March 5, 2007 - link

    The Tuniq and Scythe are supplied with 120mm fans, and we tested the heatsinks with those fans. The Thermalright does not come with a fan, so we used the best fan we had in the lab that balanced quiet and cfm, in this case the Scythe S-Flex, for testing.

    With the Scythe Infinity, we also tested the 2-fan push-pull configuration using two Scythe stock fans that are like those shippied with the Infinity. These are NOT the same fan as the Scythe S-Flex. We tested this configuration because Scythe claimed the multi-fan setup was best for demanding cooling situations and the Infinity heatsink can mount up to 4 fans.

    Introducing the fan as another variable in standard heatsink reviews changes the scope of these reviews. You can always replace the fan with a better one if it is removable, as we say in almost every review. Most fans can be replaced, but the Zalman coolers, for example, use non-removable embedded fans. We will take a closer look at 120mm fans in the future, but for now we will test with the fan supplied with the heatsink. This is how users will buy the heatsink.

    It is likely the Tuniq fan noise at full speed could be reduced by using the Scythe S-Flex instead of the supplied Tuniq fan. However, sooling effieciency of the Tuniq and Thermalright Ultra 120 are already virtually the same, and we seriously doubt the Tuniq would coold more effectively than it already does by changing to a Scythe S-Flex fan. We did try a high-output Silverstone fan on the Infinity in that review, and it did marginally improve cooling a degree C, however a high-output fan on the Infinity doid not bring the single fan Infinity even close to the cooling performance of the Tuniq Tower 120 or the Thermalright Ultra 120. THe overclocking still topped out at 3.83GHz with a single fan on the Infinity and 3.90GHz with the dual fan push-pull.
  • PICBoy - Tuesday, March 6, 2007 - link

    Hi Wesley. That was a GREAT review with totally unbelievable results and you have clarified things like the thermal compound influence on these reviews.

    Do you think the Scythe Infinity would be closer to the Tuniq 120 (like 54-55ºC) if it was mounted with the dual fan push-pull configuration usign 2 Scythe S-Flex or something stronger like 2 Scythe Minebea NMB Silent IC Series (75.9 CFM - 31.0 dBA)?
  • Wesley Fink - Tuesday, March 6, 2007 - link

    The Scythe Infinity stock fans are considerably lower output than the Scythe S-Flex fan, but they are very quiet. I suspect two S-Flex SFF21F fans in push pull would definitely improve the cooling efficientcy of the Infinity.

    However you may want to wait a few days to see a review of a new cooler from Thermaltake. It will post this week and is definitely worth waiting for.

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