360° View - Xigmatek HDT-SD964 Heatsink Information on Frostytech's test methodology is available here.
The 92mm PWM fan spins at 1200-2800RPM and draws power from a standard 4-pin PWM motherboard fan header. It is backwards compatible with 3-pin connectors. The four copper heatpipes are 6mm in diameter, and extend from the base up through all the fins. The two cuts in the aluminum base are for the AMD K8 mounting clip to lock into. The aluminum fins measure 0.37mm thick and are spaced 1.75mm apart.
The Xigmatek HDT-SD964 heatsink stands 134mm tall, and the fins allow fin is 35mm above the CPU socket for clearance. The copper heat pipes are positioned side to side at the center of the aluminum block where they make direct contact with the processor. The base incorporates an 11.5mm thick aluminum section to provide support for clamping.
The usable area of the Xigmatek HDT-SD964's base is 42x40mm in size. The four 6mm diameter copper heatpipes have been swaged into the aluminum base block, and each surface made flush by a light sanding. Surface roughness is on the order of ~32 microinches, which is considered good. Looking from the top down we can see a 4.5mm plenum behind the fan. The heatpipes are positioned towards the outer edge of the aluminum fins, directly in the path of the highest airflow from the fan.

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 Xigmatek HDT-SD964 heatsink has a roughness of approximately 32 microinches, which is considered good. The base itself has a smooth sanded finish that is generally flat in both axis. There are eight small voids created where the copper heatpipes meets up with the aluminum mounting block. These serve a positive use when the heatsink is clamped down by allowing excess thermal compound to evacuate itself from between the heatsink and processor.