360° View - Xigmatek Achilles S1284 Heatsink Information on Frostytech's test methodology is available here.
The 120mm PWM fan spins its bright orange impeller at 800-1500RPM and draws power from a standard 4-pin PWM motherboard fan header. It's backwards compatible with 3-pin connectors. The four copper heatpipes are 8mm in diameter, extending from the base up through the 40 aluminum fins. The cuts along the top of the aluminum base are for the AMD K8 mounting clip.
The Xigmatek Achilles S1284 stands 159mm tall, but the first fins are 35mm above the CPU socket for clearance. The four 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 11mm thick aluminum section to provide support for clamping. Each aluminum fin measures 0.4mm thick and is spaced 2mm apart from the next.
Xigmatek have updated the HDT base design slightly by recessing the aluminum spacers between each heatpipe. The voids between each pipe are not significant to the overall performance of the heatsink. The Achilles S1284 base has an area of 42x42mm. Looking at the top of the heatsink, we find a 7mm plenum behind the fan, and a jagged edge to the outside aluminum fins. The heatpipes intersect the fins towards the outer edge of the cooling fins, directly in the path of the highest airflow from the 120mm 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 Xigmatek Achilles S1284 heatsink has a surface roughness of approximately 48 microinches, which is considered good. The base surface has a sanded finish that is generally flat in both axis. More importantly, all five components (four copper heatpipes and the aluminum block) are flush with one-another. The heatpipes are slightly offset as you can see.