Zalman CNPS9900DF Dual Fan Flower Heatsink

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The most critical aspect of installation is that the heatsink be securely mounted. A firm mating results in good contact between the heatsink's base and the CPU heatspreader and more efficient heat conduction. Ideally it should also be a simple procedure with the user having to handle as few pieces of hardware as possible.

The 9900DF employs the same mounting system as its predecessor, the MAX. For Intel systems, a lug nut is inserted into each corner of the backplate through the appropriate hole depending on the socket. A plastic brace goes over it to lock in place for mounting.

Bolts are then used to secure the lug nuts to the clips but because the heatsink hangs over them, it's hard to get to. To make it easier, Zalman uses bolts with shallow hexagonal threads and includes an Allen wrench in the package. It's a real pain as the wrench is impeded by board components like the VRM heatsink, while the long end can only engage the screw head at an angle. Also note how the mounting clips bend downward, putting most of the pressure around the perimeter rather than the center of the CPU.

Typically we tightening the bolts down as much as possible to give every heatsink the best possible chance but we ended up wearing down the hex head threads easily. We then had to find a different Allen wrench to remove them which proved to be a major task as the thread size is very small. Oddly, we didn't run into this problem with the CNPS9900 MAX despite it having the exact same system. After re-examining the whole mounting system and process, both Mike Chin and I concluded that stripping the head threads of these tiny bolts is more normal than not; we were just lucky that it didn't happen with the CNPS9900 MAX... unless those bolts had better threaded heads.

One nice thing about the 9900DF is it doesn't take up that much room. There is about 40 mm of clearance below the bottom fin but the body is fairly narrow so it didn't interfering with anything.

An adapter is included to run both fans off a single motherboard fan header but the larger center fan is a 4-pin PWM model while the front fan is an old school 3-pin. Using PWM control, the 3-pin fan runs at full speed.

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