Zalman CNPS9500 LED heatsink/fan

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The basic design of the CNPS9500 is a Zalman 7000 turned sideways and perched on heatpipes. The design is a good one: Embedding the fan inside the heatsink allows every bit of airflow from the fan blades to dissipate heat.

The CNPS9500 is a clever evolution of the CNPS7000 design.

The diameter of the "flower" is the same as the Zalman 7000 series, and a similar 92mm fan is used. Like the 7000, the flower is incomplete; roughly a sixth of the circumference is left open to leave room for the heatpipes. The fins are bigger than the ones on the 7000, so the total surface area of the fins ? and the cooling potential ? is greater. It has the biggest cooling surface area of any Zalman HS: Zalman cites 3,698 cm2 for the 9500. The 7000 series heatsinks come in at 3,170 cm2, and the 7700 is 3,268 cm2.

The CNPS9500 turns the design sideways and elevates it above the motherboard where there is less chance of interfering with the other components.


The 9500 weighs only 530 grams, compared to 775 grams for the all-copper 7000cu or 918 grams for the 7700cu. The difference is the "tunnel" through the center of the 9500, which is devoid of any metal. In the 7000 and 7700 series, this center forms the solid, massive base. In comparison, the base on the 9500 is a small copper plate and an aluminum top plate with the heatpipes clamped between them. Aside from the weight reduction, a second advantage of this design is that air flows through the heatsink with little impedance. This means that all of the fin surface area can work efficiently to dissipate heat, and there is very little ineffectrive turbulence cause by sharp angle turns in airflow direction.

The center is hollow, allowing air to pass.


Unlike most "tower" style heatsinks with fans that blow across the motherboard, airflow is not ducted from one end of the heatsink to the other. Instead, air can escape from all sides, including the top and bottom. This means that a substantial amount of air should end up being blown down towards the VRMs (Voltage Regulation Modules) that usually surround the CPU socket, cooling them in the process. This is important, as ATX motherboards are designed with this kind of cooling in mind; many tower-style heatsinks risk shortening the life of the motherboard because they tend to block the airflow from reaching these components.

The fins are anchored to three heatpipes that rise gracefully up from the base in a figure 8. The fins are attached to the middle of the heatpipes, while both ends are attached to the base. The flow of heat inside the heatpipes is from the ends to the middle.

Both ends of each heatpipe are attached to the base and rise up in a figure eight.

Zalman has made excellent use of the heatpipes. The distance from a heatpipe to the edge of a fin is never much more than a couple centimeters, which means that there are no "dead spots" on the fins; just as the embedded fan spreads the airflow evenly across the fins, the heat is also evenly distributed.


The fan, looking up from the bottom of the heatsink.

The LED fan is mounted on a steel bracket that positions it just above the top of the fins. On our sample, the fan was slightly off-center. This has no practical downside, but it suggests that the manufacturing process by which the heatpipes are formed probably isn't quite perfect yet.

The fan blows through the heatsink, so care should be taken to install the heatsink in the right orientation. The mounting system allows the 9500 to be installed "facing" any of four directions. Ideally, the empty side of the heatsink should face the rear case fan, so that the hot air coming off the heatsink is immediately exhausted.

Zalman rates the fan at 0.35A and 2600 RPM, quite high for a fan that is supposed to be quiet. In comparison, the 92mm fan in the 7000 series is rated for 0.23A and 2400 RPM. It is also a dual ball-bearing fan, which is usually not the best choice for noise, although a quieter sleeve-bearing fan would not be as reliable for use in a high-heat application like a heatsink. As with all their CPU heatsinks, Zalman ships a Fanmate 2 fan controller with the CNPS9500, so the fan can be easily undervolted down as low as 5V.

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