the heat output from intel processors varies widely between single and multi-core processors, so we've settled on two values which represent the upper limit of both existing CPU families. With a 150W heat load applied by the Intel LGA775 version of FrostyTech's synthetic thermal test platform, the Zalman CNPS9500 AT heatsink yields a very nice rise above ambient temperature of 29.6°C! For this thermal result, there was 53.3dBA noise from the 92mm fan spinning at its full speed of 2650RPM. The CPU equivalents of this test would be an Intel Pentium D / Extreme Edition or Core 2 Quad class chip.
The Zalman CNPS9500 AT heatsink was also tested with the reduced heat load of 85W. In this situation the heatsink produced a 17.3°C rise over ambient at full fan speed.
No low fan speed thermal tests were conducted.
This is due the fact the PWM fan was determined to be rotating below minimum design criteria when a standard 3-pin fan speed controller was applied. This will probably be an ongoing issue with socket 775 Intel heatsinks and most PWM fans.
In any case, Pulse Width Modulation fans certainly bring a lot of positive attributes to the table, so there is no reason to avoid them just because of the challenges in testing that we've described.
When a PWM fan is attached to a motherboard that has a 4-pin PWM CPU fan header, the BIOS is able to control fan speed in direct correlation to the thermal output of the processor. On the plus side this reduces computer noise; it can also create a situation where the fan spins up and slows down with annoying regularity as Windows XP or Windows Vista goes about its behind the scene duties...
From the results listed above, it's clear that the Zalman CNPS9500 AT heatsink offers better thermal results than the stock Intel Pentium D heatsink, though at a slightly higher noise levels - 53.3 dBA vs. 47.5 dBA. However, on both the 150W and 85W head loads, the CNPS9500 AT heatsink maintained lower temperatures, and with a PWM-compliant system we would expect fan speeds to scale down too.
For more reviews on the latest heatsinks and cooling solutions, rely on FrostyTech's inventory of 350+ heatsink reviews. Here are a few other articles that you might enjoy as well...
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