TweakTown has done a review on the MOS Circular Copper Shim - Basically, a shim (aka spacer) is designed to stabilise the standard socket 7/370 HSF´s on FCPGA Intel Pentium III Coppermine and Celeron II processor cores so the HS doesn´t sit on an angle. If the HS is seated on the core on an angle, the HS will not be as effective and will also increase the temperature.
MOS Technologies ( http://www.mos.net.au) based in Brisbane, Australia sent us down one of their MOS Circular Copper Shims. So, what´s a shim? Well, there is an issue with the FCPGA Coppermine PIII processor and standard socket 7/370 heatsinks. The problem is that the center, raised slug on this processor is not very large and a standard socket 7/370 heatsink can rock back and forth on it losing some important contact which can cause higher temperatures. This spacer (or shim) sits around the center slug (core) on the CPU and levels the surface so the heatsink gets a tight fit. The material is copper, so it also transmits heat while helping to cool areas around the center slug that otherwise go completely uncooled.Read more
