So I've been doing a bit of overclocking testing and I discovered something strange with this heatsink. While my case was closed with the fan at 100% it would actually get warmer then when the fan was at 20%. Turning up my case fans results in lower CPU temperatures, but still raising the speed of the fan on the heatsink results in overall higher temperatures of the CPU.
I can only surmise the fan on this heatsink is actually really terrible at doing it's job. It may seem like a no brainer when you look at the thing, but it effectively blows more air around the sides then through the actual heatsink. It's entirely possible to design a shroudless impeller that directs the airflow, Zalman appears to have not done this here.
Interestingly, the fan works better when the side of my case is off. Turning it up reduces temperature levels and it almost functions like a normal heatsink.
Amusingly I made a half assed cardboard shroud, which amounted to a piece of cardboard wrapped halfway around the heatsink, loosely, and it dropped my temps by 12c~ under load while the side of the case was on.
I replaced a CNPS9500 with this thing. Looking at that heatsink once again, I think the CNPS9500 may have cooled better. The testing I did at that time must've been with the case panel off and I believed the reviews, which are of course, done on a option testbench.
