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: 1.5V
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 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 Scythe Andy Samurai Master reached just 3.81 GHz, which is middle of the pack and competitive with the much cheaper Thermalright MST-6775 and the Scythe Katana. The Thermalright MaxOrb barely did better at 3.83 GHz. With most of the better coolers reaching 3.90 to 3.94GHz these results are somewhat disappointing.

Since the Scythe Andy Samurai Master allows easy fan swapping, we did try a number of fans with the cooler. The supplied Scythe fan is only about 50cfm compared to the 90 for the MaxOrb on high. The Scythe S-Flex SFF21F (63.7cfm), the SilenX IXTREMA (72CFM) and the Aero Cool Xtreme Turbine (89.39cfm) were all tested with the Andy Samurai. To our surprise none of the three would allow the Andy Samurai to reach higher than a 3.81GHz overclock. Apparently the close spacing of the fins is optimized for a medium output fan and more airflow just will not improve performance.

One of the arguments for down-facing coolers is that they should cool board components better than the side blowing heatpipe towers. Lower board component temperatures should allow a higher overclock, at least on paper. The unfortunate reality so far, with all the down-facing coolers tested from the Cooler Master GeminII to today's MaxOrb and Andy Samurai Master is that these down-facing coolers just do not cool as well as side-blowing heatpipe towers. Since cost is about the same as the best heatpipe towers we have tested, you really don't get great value with the down-facing designs.

Scaling of Cooling Performance Noise
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  • Ver Greeneyes - Tuesday, June 5, 2007 - link

    That's exactly what I said a few posts above.. I don't understand this setup. I think the best setup for a top-mounted fan would be if you've got another fan that blows air into the heatsink, which said fan then pulls away out of the case.
  • SurJector - Monday, June 4, 2007 - link

    I suspect the components on the MB do not need that much cooling. Some air, even warm, is better than none, but there is probably no need for much more.
  • MageXX9 - Monday, June 4, 2007 - link

    Does anyone else stop even considering a heatsink when I see those horrible push in clips that are the same type as the retail heat sink fan? I recently built my first Core 2 Duo system and was horrified at what a horrible design. The instructions had in big bold letters that it should only be installed when the motherboard is already in the case, but the amount of force needed to get each one to click, and the way my motherboard flexed made me vow to never use those types again.

    So, if I don't see a screw down design that isn't plastic I immediately write it off.

    What does everyone else think?
  • kmmatney - Monday, June 4, 2007 - link

    It's not just you. I was horrified when I built my first Socket 775 system. What a pain those plastic clips are! I'm always afraid I'm going to break something, or break something on the motherboard with the force needed to snap them into place. I've been putting off pin-modding my E4400 because I don't want to go through the hassle of removing my HSF.
  • Imnotrichey - Monday, June 4, 2007 - link

    I just dealt with those clips for the first time, 2 weeks ago on my new system. What a hassle! First, I couldn't get them all in together at once. Then finally when I do get them in, one stays out!! so I try to restart, and then I can't pull one of the pegs out, I felt like I was going to rip the mobo out before I was going to pull out the stock HSF. Luckily, I got it once I turned the case at a certain angle so I could get a good grip. Turns out one of the pegs wouldn't go down all the way. A little piece of plastic was coming up in between the peg, pushing them apart.

    I had to get an Arctic Cooling Pro 7, still had some issues, but eventually got it right. But definetly never want to have to fool with those screws again :)
  • sofarfrome - Monday, June 4, 2007 - link

    ...what was ambient temp during this (and other) tests? Everytime I look at the chart that compares 22 or so HSFs I see where 3 products I use always are at the top of the list (Tuniq, Scythe Ninja RevB, and now the TR Ultra 120 extreme). However, obtaining the temps Anandtech claims at 1.5875vcore is a little difficult to believe. That must be one hella cool running x6800.
  • Wesley Fink - Monday, June 4, 2007 - link

    The ambient room temperature is maintained at 20 to 22C, which is 68 to 72F. We measure ambient room temp before we begin any temperature tests. In the summer we have to turn off almpst all the equipment in the test room to keep the temperature from rising during the tests.

    The fans used with this 3 top coolers definitely improve the cooling with these heatpipe towers. You might want to refer back to the original reviews.
  • DaveLessnau - Monday, June 4, 2007 - link

    quote:

    We do not use auxiliary fans in the test cooling case


    If I'm reading that correctly, that means you tested without a case fan. This is definitely a problem. Without a case fan, the only way to get hot air out of the case would be because of overpressure. With nothing moving air into the case, there'd be no overpressure and thus no heat exhaust. Properly oriented side-blowing heatsink fans would provide some exhaust, but the down-blowing ones wouldn't be able to do that. Essentially, without that case fan, this test is designed to cause down-blowing heatsinks to fail.
  • Wesley Fink - Monday, June 4, 2007 - link

    The large area behind the CPU is perforated in the test bed case so air can definitely escape due to heat rising and gravity flow. We just don't use a case fan to push the air out. It also seemed a possibility to us that we were not exhausting air as well with the down-facing fan coolers, so we also ran a few tests with the case on the side and the side (now the top) off. Cooling performance and overclocking did not improve at all.

    We are looking at all your suggestions to incorporate the best ideas in the new cooling test bed.
  • lopri - Tuesday, June 5, 2007 - link

    Incredible argument. (umm.. Gravity?) Are you suggesting that we can do away with the probably single most important fan in ATX design philosophy?

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