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: 2.20V
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 memory speed of DDR2-800. As the 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 Enzotech Ultra-X reaches a stable 3.86 GHz - again similar to other down-facing coolers. This is high enough to make the Ultra-X the best overclocking down-blowing cooler we have tested, but it does not match the 3.90 to 3.94GHz measured with the best heatpipe towers.

Many readers have suggested that an auxiliary case fan exhausting air out the back of the case will improve performance of the down-facing fan coolers. As an additional check we mounted an Aero Cool 120mm Xtreme Turbine fan at the rear of the case exhausting air form the case interior. This fan is capable of air flows up to 89 CFM.

The added case fan did cool temperatures by as much as 4 to 5C at stock 2.93 GHz, and 1 to 3C at 3.83 GHz. This did provide somewhat better cooling with the Ultra-X. However, we could not achieve a higher overclock with the Ultra-X with the added high-output case fan. The highest stable overclock was still 3.86GHz.

Scaling of Cooling Performance Noise
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  • homonaut - Wednesday, June 27, 2007 - link

    I was contemplating getting one of these after stumbling onto this 'review': http://www.coolaler.com/modules/news/article.php?s...">http://www.coolaler.com/modules/news/article.php?s... but now I don't know. How can the results be so different!?
  • SilthDraeth - Wednesday, June 27, 2007 - link

    Since I don't speak Chinese or Korean, etc, all I could do was look at the pictures. It is unclear what temps are load or not.

    Also, they use different processors. Anand uses a 6800 vs a 6600.
    They both post a 43 degree celcius temp, on Anand thats a load temp at stock speed, so that might be load on the coolaler site. and the lower temps might be idel temps for the 6600.
    idle temp might have been taken at a different time frame for how long the processor was running before the temperature was taken, etc.

    The temps do not look to be a huge disparity though imo.
  • Wesley Fink - Wednesday, June 27, 2007 - link

    The Enzotech could boot as high as 3.90 GHz, which is as good as any of the best coolers tested except the Ultra-120 eXtrme which reaches a stable 3.94GHz. All was fine at idle at 3.9GHz, but as soon as we began our stress testing with the game that is about 80% CPU load the system would fail with the Enzothec. This was with the fan on high, near 90 cfm at a pretty loud noise level. We could not even make it through one loop of the game demo, and our stress test procedure runs the game loop for 30 minutes to test load stability.

    We also tried adding a high output case can as some readers have suggested. This DID lower the CPU temperature, particularly at stock speed strangely enough, however it did not extend overclocking ability at all.

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