360° View - nPowertek NPH-775-140HC Heatsink Information on Frostytech's test methodology is available here.
The 95mm diameter PWM fan spins its impeller at 1500-3000RPM and draws power from a standard 4-pin PWM motherboard fan header. It's backwards compatible with 3-pin connectors. The 33mm diameter copper heat column at the center of the heatsink body extends all the way to the base. The extruded aluminum which surrounds the heat column is 90mm in diameter, though each side is comprised of 2.5mm of aluminum and ~26mm long straight bifurcated cooling fins. Each fin is 0.8mm thick and spaced 1.0mm apart at the base. The tips of the bifurcated fin are a scant 0.5mm thick, and spaced 1.0mm apart.
The nPowertek NPH-775-140HC heatsink stands 72mm tall. Air is exhausted outwards from the cooling fins, where it can then be used to cool adjacent board-mounted components. Most socket 775 Intel motherboards are designed to use this source of airflow, and so VRM and chipset heatsinks are often passively cooled.
The copper base of the nPowertek NPH-775-140HC heatsink is 39mm in diameter where it makes contact with the processors' integrated heatspreader (IHS), and at least 6mm thick. The base is turned perfectly smooth, but the surface is very slightly domed at the center.

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 nPowertek NPH-775-140HC heatsink has a surface roughness of approximately ~8 microinches, which is excellent. The base surface itself has a polished finish, but is very slightly convex at the center.