Readers who tenaciously seek silence in their PC will probably recognize the Thermalright Ultra 120. It is not exactly the same heatsink, but it is similar in appearance to the HR-01 fanless cooler introduced by Thermalright in late 2005. That cooler shipped for AMD only, as we were still in the hot Intel Prescott days. Adapters were introduced later to allow HR-01 to mount on newer sockets, and HR-01 is still in the Thermalright product line as a fanless cooler.


However, there is no way to even mount a fan on the early versions of HR-01, so its appeal was limited to users seeking silence at around stock speeds. Overclockers really had little use for the HR-01. Thermalright recognized that a cooler designed to perform well with no fan could be very attractive to overclockers if there were some means of active cooling, and so the Ultra 120 was born.


The Thermalright Ultra 120 refines the shape of the HR-01 and adds the ability to mount a 120mm fan to the heatsink tower. If you look closely you can see that the cooling fin edges are turned up on one end and turned down at the other end of the same fin. This creates airflow patterns that are refined in subtle ways from the more common flat fins. Unlike the HR-01 the Ultra 120 is designed to operate with a 120mm fan. The heritage, however, is the fanless HR-01 design, and we will also evaluate the Thermalright Ultra 120 as a fanless design.

Since no fan comes in the Ultra 120 kit the buyer is free to select the fan that best serves their needs. This is something of a "gotcha" in the Ultra 120 design because the fan wires are designed to clip into the lower holes on a 120mm fan post.


The problem with this design is that fans with a full post, which are most of the fans available in the lab, will not mount on the Ultra 120. You have to use a fan with holes instead of a full post. Fortunately two of the better fans that are available, the Noctua and the Scythe S-Flex, both use the 4-hole design.

There are also some advantages to the fan clip design. Since the wire clips on the bottom of the fan you can use a 120mm fan of any thickness; You are not limited to 25mm. That is if you can find the fan in a postless design.

The Noctua fans are an excellent choice for a silent PC. One of the available Noctua fans even has a noise rating of 8dB-A. Since our goal was maximum overclocking along with reasonable quiet the Scythe S-Flex was chosen in the highest RPM version that was available. This was the 1600rpm, 63.7 CFM SFF21F. The S-Flex uses the Sony Fluid Dynamic Bearing design for the fan motor instead of ball bearings or sleeve bearings.


The Sony FDB should translate into a quiet fan, even at higher speeds, and it has a very long fan life. Scythe specifies the fan life as an incredible 150,000 hours. Even with the high CFM rating the Scythe SFF21F is still rated at a quiet 28dB-A, which is well below the noise floor of our test system's power supply. The Thermalright Ultra 120 and Scythe S-Flex SFF21F were both provided for review by Frozen CPU. This means both items are straight off the retail shelf.

The advantage of using after market fans is you can choose the fan based on your system goals - silence, overclocking, or a combination of both. The disadvantage, of course, is that you need to buy a fan to go with your heatsink, where complete kit designs have a fan that is matched by the manufacturer to the heatsink. Both approaches can be argued, but the fan is a cost in addition to the heatsink cost. 120mm fans can cost as little as $3, but the S-Flex was about $15 and the Noctua fans sell for as much as $25.

With the Thermalright Ultra 120 and Scythe S-Flex combo there are several questions to be answered in our tests. Does the Ultra 120 live up to its billing by many users as the best heatsink you can buy? How does the Ultra 120 compare in overclocking abilities to the best heatsink towers tested at AnandTech? Since it is based on a fanless design, can the Ultra 120 be used as a fanless and zero noise CPU cooler?

Thermalright Ultra 120
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