Overclocking

In the review of the Thermalright Ultra 120, which matched the 3.90GHz highest overclock of the best tested coolers, we concluded that the maximum stable overclock of this X6800 processor on air was likely 3.90GHz. This looked reasonable considering the dual-fan Scythe Infinity, the Tuniq Tower 120, and the Thermalright Ultra 120 all topped out at 3.90GHz. Other heatpipe towers all topped out below this threshold, with the better coolers very close to the 3.90GHz plateau.

We were wrong. Better air cooling was possible and we are seeing what that cooling can do for overclocking in the performance of the Ultra 120 Extreme. It is all about cooling, and 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: 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 Extreme with the Scythe S-Flex fan set a new overclocking record by maintaining a stable 3.94GHz. This is the highest stable overclock we have reached with air cooling with this CPU. We could boot at speeds as high as 4.0GHz, but gaming performance was not stable at speeds higher than 3.94GHz. Increasing the CPU voltage also did not increase stability above 3.94GHz, as 1.60V was the maximum voltage usable without generating random reboots of the system.

The best coolers prior to the Ultra 120 Extreme have topped out at 3.90GHz. The 3.94GHz with the Ultra Extreme was something of a surprise, but it proves again that if you move enough air and use enough heatpipes in a good design you can further improve air cooling. Eventually the limit will be reached with air cooling, since it is not an active cooling solution. Air cooling cannot cool lower than the ambient temperature of the room, and it will therefore be outperformed by some active cooling solution like TEC or phase-change cooling. Water cooling is also limited by ambient temperature, but liquid is a better medium for absorbing and releasing the heat produced in CPU cooling. This is also part of the principal used in the design of heatpipes that are proving effective in the current crop of heatpipe towers.

At a 3.94GHz maximum overclock the Thermalright Ultra 120 Extreme is the best air cooler we have tested at AnandTech. It is clear Thermalright knew what they were doing in modifying the Ultra 120 design with additional heatpipes.

Scaling of Cooling Performance Final Words
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  • PICBoy - Thursday, March 8, 2007 - link

    Oops! actually on every table and image the name "PLUS" is used instead of Extreme. My bad, that's all!
  • Spoelie - Wednesday, March 7, 2007 - link

    For the quieter power supplies, I'd look at the Seasonic S12+ series, and the Corsair HX series for a higher powered system.

    Why? That particular Seasonic is by many a reviewsite considered to be one of the quietest around, and starts ramping up the fan around 250w (depending on how much case cooling you have). The corsair is ~2dB louder in the low wattage scale, but only starts ramping up around 300w given the same conditions.

    The ramping-up spot is pretty important, for example, before I had a Venice+x850xt and CM RealPower psu, this proved to be a pretty quiet combination. However, once I upgraded to an oc'd denmark+x1950xt, idle power jumped up and the PSU was already ramping up during idle. It only got worse under load, and I couldn't stand the noise at all. I replaced the PSU with a Corsair HX and have yet to actually hear it ramp up, the other TC fans in the system drown out any noise it makes.

    A passively cooled mobo is standard these days, and a minimum of case airflow should be considered as well.
  • Frumious1 - Wednesday, March 7, 2007 - link

    Noise and performance tend to be conflicting goals. Sure, you can get a passively cooled motherboard, and with a down-facing PSU fan you can probably go fanless on the CPU (with something like an Ultra 120/120+). You should probably still mount a low RPM case fan, however, as a "good" PSU that doesn't ramp up fan speed is also not going to move a lot of air.

    The problem is, if you want to overclock all of that silent/fanless stuff becomes much more difficult (if not impossible). 680i motherboards are known to use quite a bit of power, and the chipsets definitely require active cooling if you want to do some real overclocking. Then you get higher CPU temperatures, and without active cooling on the CPU you tend to rapidly increase temperatures until the system crashes/shuts down.

    The cooling test bed appears to be configured as a reasonable compromise between extremes. Some people want silence, some people want performance and quiet be damned, but most are just looking to build a reasonably fast and reasonably quiet PC - hopefully without breaking the bank. Besides, as Wes mentions above, SPCR already covers the "silence above all" market quite well. Why go up against them when there's a vast user base that has more moderate needs?
  • Spoelie - Wednesday, March 7, 2007 - link

    The thing is, with the right aftermarket parts, you can have a totally silent pc AND a high performance/overclocked one. There isn't a need for compromise, as long as you don't want to break any world records. I mean, even in this review, they have a core2 duo overclocked to 3.9ghz without any case air flow. I call that pretty high performance.

    http://www.jaha.be/ashop/?mod=product&cat_id=5...">http://www.jaha.be/ashop/?mod=product&cat_id=5... Thermalright HR05 for the chipset, this is a passive heatsink that dropped my chipset temperature 10°C over the standard HSF combo. Granted, I only have the DFI nForce4, but there are plenty of high performance alternatives for the 680i. Thermalright also has a good passive cooler for scorching hot ram: http://www.jaha.be/ashop/?mod=product&cat_id=5...">http://www.jaha.be/ashop/?mod=product&cat_id=5...

    Choose a good case like the Antec P-series, put the silent psu's mentioned earlier in there, change the exhaust fan for a nice 1000rpm nexus/papst, get the reviewed heatsink (or a tuniq/scythe, it's not like i'm a thermalright fan) with another 1000rpm nexus/papst and you're set. All modern gpu standard cooling solutions can be made extremely quiet at idle with some software tweaking, so you'll only hear them when you're gaming. I guarantee the above combination will support heavy overclocking and be extremely quiet at the same time.
  • Spoelie - Wednesday, March 7, 2007 - link

    Hmmm just want to add that you do have a point about the moderate user not going to put all that aftermarket stuff in their pc, so the thing about the differing user bases is right. On the other hand, a moderate user isn't going to provide extra active cooling to overclock (or even have) a 680i.
  • Baked - Wednesday, March 7, 2007 - link

    Nice review. Have the Ultra-120 on my C2D system. When I get the chance to get a C2Q, the Ultra-120+ is going in there.
  • nrb - Wednesday, March 7, 2007 - link

    ...is you need to actually benchmark the Tuniq Tower using the same S-Flex fan.
  • Wesley Fink - Wednesday, March 7, 2007 - link

    One more time. If a cooler comes with a fan we test with that fan. We chose the S-Flex because the Ultra 120 and 120+ do NOT come with a fan, and the other fans we had available would not fit the Ultra 120/120+ clips. We may well test 120mm fans in the future, but we do not plan to do cooler reviews using several different aftermarket fans as a routine test procedure. We do our best to test the cooler as shipped.

    Having said that, it is likely a good idea to compare a few of the top-performing coolers using the same top-performing fan in a separate review. We agree that would be interesting.
  • PCTechNow - Wednesday, March 7, 2007 - link

    Why not go back and test the other coolers with the same fan used in this review? It would at least show if the fan or the cooler is making the difference. Better yet, take the fan off the Tuniq and test with it on the Thermalrights and see what the difference is.
  • dm0r - Wednesday, March 7, 2007 - link

    Air cooling is gettin better and quieter this days...good to see a cooler that improves them both.I was choosing tuniq tower for my next desktop system but i liked the Thermalright ultra 120 in Noiseless cooling.Thanks AT for this review.BTW Any results difference between 120 and 120+ in noiseless cooling?

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