http://www.amd.com/us-en/assets/con...oling_guide.pdf

The cooling guide does mention grease. Note that the guide is dated 4/2000. It is obviously out of date. I bet it applied to the Slot-A Athlons.

If you look at the AMD Thermal, Mechanical, and Chassis Cooling Design Guide, page 13 lists the suggested interace materials. All of them on the list are phase change materials.

http://www.amd.com/us-en/Processors...30_182_869_1039^1065,00.html