360° View - Intel FCLGA4-S Reference Heatsink Information on Frostytech's test methodology is available here.
The Intel FCLGA4-S reference heatsink is built with an integrated 110mm diameter fan that spins at speeds of 2900RPM in "P" mode, 2000RPM in "Q" mode, and as low as 1000RPM on PWM compliant motherboards. Power is supplied by the 4-pin PWM fan cable which connects to a standard 3-pin or 4-pin motherboard fan header. The 134mm diameter body of the heatsink frame provides a small measure of protection to the impeller from errant wires. With the fan removed, the unique design of Intel FCLGA4-S reference heatsink is clearly visible. The 41mm diameter copper cylinder is a hollow thermal camber which works in the same fashion as a heatpipe. Each aluminum cooling fin is 0.3mm thick and spaced 1.0mm at the base, 3.0mm apart at the tips. Note the space at each corner to allow some access to the retention clips.
The body of the Intel FCLGA4-S reference heatsink stands ~81mm tall, with an overall height of ~91mm. The four push-to-lock plastic clips lock directly into the motherboard mounting holes which surround the LGA775 processor socket. The fan mode switch is tucked away along the side of the FCLGA4-S heatsink where it's easy to access. The body of the cooler fans out from 89mm in diameter about 45mm above the board (thus providing clearance to adjacent components) to 134mm in diameter.
The copper base of the Intel FCLGA4-S reference heatsink measures 29.5mm in diameter where it makes contact with the CPU's integrated heatspreader (IHS), and is about 4mm thick. The heatsink ships with a thin grey pad of thermal interface material pre-applied. The copper is machined perfectly flat, with a ridged surface texture. The widely spaced thin aluminum fins offer little in the way of air resistance. This design works under the principle that components around the processor socket are also cooled by this heatsink's exhaust airflow.

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 copper base of the Intel FCLGA4-S reference heatsink is machined to a perfectly flat surface in both axis. Surface roughness is approximately ~63 microinches, owing to a purposefully ridged surface texture. The smaller, 29mm diameter circular pad at the center is raised 0.4mm to contact the processor (the outer 43mm copper pad doesn't touch).