360° View - Zalman CNPS8900 Extreme Heatsink Information on Frostytech's test methodology is available here.
The 110mm fan PWM spins at 2800-1250RPM and draws power from mini/standard 4-pin fan header. The seven-bladed translucent impeller directs airflow downward so components surrounding the CPU socket are cooled as well. Removing the fan gives us a clearer idea of how the 121mm diameter CNPS8900 Extreme heatsink is constructed; aluminum fins are soldered to a cast aluminum base while two heatpipes wrap around the circumference of the fins at two points... then the entire heatsink copper plated. Each copper plated aluminum fin is 0.4mm thick and spaced ~2.0mm apart at the edge.
Standing 60mm tall and 121mm in diameter, the Zalman CNPS8900 Extreme is a very compact heatsink. Note the two 6mm diameter copper heatpipes that wrap around the bottom ~82mm dia. and upper ~112mm dia. lips of the cooling fins.
The base measures 32x32mm in size and is comprised of exposed copper heatpipes and the copper plated cast aluminum sub base the heatpipes and fins are soldered to. The base has a lightly sanded finish.

Base Finish and Flatness

Flipping a heatsink over to inspect the business end is often a simple indicator of overall cooler quality. More practically speaking, a heatsink is in many ways only as effective as the contact it makes with the processor - the flatter and smoother the better. Base finish is one of the criteria that Frostytech measure in the course of evaluating heatsinks, and it involves two distinct aspects. Surface Finish is the first; this is calculated with the aid of Surface Roughness Comparator that has a cross section of common machine surface finishes and their numerical surface roughness equivalents in microinches. The second is Surface Flatness. This is tested with an engineers straight edge or proven flat surface, in two axis.

The base of the Zalman CNPS8900 Extreme is copper plated aluminum with two exposed copper heatpipes. The base is 32x33mm in size with a lightly sanded finish. Surface roughness is at or better than approximately 32 microinches. The base is generally flat in both axis, but since it has not been machined all elements are not perfectly flush with one another.

Next up, Frostytech heatsink sound level measurements...