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  Keeping that hot CPU running cool and quiet 
  Jan 05, 2005, 08:30am EST 
 

Turning the heat on


By: Sander Sassen

Processor cooling is and always has been a topic of much debate. Many enthusiasts advocate the benefits of watercooling your PC whereas others will tell you that phase change refrigeration is the holy grail of processor cooling. In reality the vast majority of PCs still use a simple heatsink and fan to keep things running cool and will continue to do so in the future as well. With the arrival of processors such as Intel’s Pentium 4, featuring the fiery 90nm Prescott core, modern heatsinks however have much better performance then their predecessors, but they still rely on the same principle of forcing air over fine fins to dissipate the heat away from the hot processor.

With the arrival of socket-775 for Intel’s Pentium 4 and socket-939 for AMD’s Athlon-64 we’ve entered a new high in processor cooling requirements, with processors capable of generating over 100-watts of heat. Obviously we can get by with older designs to get rid of the heat, but that would mean having to force more air over the heatsink, thus higher rpm fans to cool them. Given the fact that the majority of users want their PC to be both fast and quiet that isn’t the best solution. Hence heatsink manufacturers have pulled a few tricks out of their hat to keep the current generation of processors running cool and quiet. Let's have a look at two popular heatsinks from two well-known manufacturers to see whether they're up for the job.

Stock Intel top view

Stock Intel side view

The stock Intel heatsink for socket-775, small and noisy by comparison.

One of the manufactures that is known for their innovative cooling solutions is Zalman, and they’ve just released their CNPS7700-Cu, a larger version of their popular flower shaped all-copper heatsink. To generate plenty of airflow over the heatsink to keep the processor running cool it is equipped with a 120-mm fan. With that 120-mm fan the heatsink itself has also been increased in size and now looks like a CNPS7000-Cu on steroids. With compatibility for socket-775, socket-478, socket-939 and 940 as well as socket-754 this new heatsink is ready to mount to your motherboard of choice and by the looks of it will be able to handle the hottest processors with ease, but keep quiet about it.

Zalman CNPS7700-Cu top view

Zalman CNPS7700-Cu side view

The Zalman CNPS7700-Cu, all copper heatsink with 120-mm fan.

Another well-known manufacturer, ThermalRight, has been selling a heatsink capable of accommodating a 120-mm fan for quite some time now. It actually was the first heatsink to be introduced that had this ability and as we’ve seen with good ideas before, others followed suit. Their XP-120 heatsink uses a combination of a copper base, fine aluminum fins and no less than four heatpipes to remove the heat from the processor. It will come as no surprise to you that this soon became the heatsink of choice for anyone looking for the best in air cooling. And as we can relate from a previous evaluation, a XP-120 teamed up with a 120-mm fan of your choice is no slough in the performance department, easily keeping pace with the hottest Pentium 4 Prescott processors.

ThermalRight XP-120 top view

ThermalRight XP-120 side view

ThermalRight XP-120, featuring heatpipes, aluminum fins and a 120-mm fan.

Naturally we’d like to see how these heatsinks fare with a variety of processors, including the socket-775 and socket-939 platform. We’ve opted to use a socket-939 90nm Athlon 64 3500+ processor and a socket-775 90nm Pentium 4 processor at 2.8GHz as well as a socket-939 130nm Athlon 64 FX-55 and socket-775 90nm Pentium 4 3.6GHz processor to see how well these heatsinks perform with midrange and high-end processors. Obviously we used a fan on the XP-120 that has comparable performance to the one featured on the Zalman CNPS7700-Cu and gauged performance at high-rpm and low-rpm settings using the supplied Zalman fanmate controller. We measured temperatures in a typical, well ventilated, mid-tower case with the processor running at full tilt crunching away at Prime95 and SETI@home after 30-minutes of settling in. To give you an indication we’d also like to note that idle temperatures where typically 10 to 15 degrees lower than full load temperatures.


As can be seen from the graphs the Intel Pentium 4 560, at 3.6GHz, lives up to its name and would truly be blistering hot if it weren’t for the capable heatsink fitted. With the stock Intel heatsink the processor touches upon 70-degrees Celsius when taxed and that’s a bit too much as it start to throttle at that speed and that really puts the brakes on performance. The Athlon 64 FX-55 is also turning up the heat but not quite as much as the Pentium 4 processors. The one processor that remains fairly cool, even when running at full steam, is AMD’s 90nm Athlon 64 3500+. What also is clear from the graphs is that the ThermalRight XP-120, fitted with a 2200-rpm Papst 120-mm fan, manages to beat the Zalman CNPS7700-Cu by just a tiny margin. Overall noise production was close to inaudible for both heatsinks at the 1100-rpm setting, the noise simply drowns in the noise generated by the power supply fan and harddisk. At 2200-rpm both upped their noise production by a tad, but still well below what the stock heatsinks produced.

Overall we have a hard time picking one heatsink over the other. The Zalman is attractively priced and comes complete with fan, fan speed controller and mounting material for all socket types supported. The ThermalRight can be outfitted with a 120-mm fan of your choice, offering greater flexibility and offers slightly better performance. It however does not come with a mounting bracket for socket-775 or fan, which need to be bought separately. Due to its low cost and completeness the Zalman CNPS7700-Cu has our preference, but the ThermalRight XP-120 will certainly appeal to those wanting a bit more control over the fan type mounted, and thus cooling performance, or in those cases where the Zalman does not fit your motherboard.

Sander Sassen.



1. Turning the heat on
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