The other notable innovation with Intel's FCLGA4-S reference heatsink is harder to see, a vapour chamber. At 413grams, the vapour chamber also makes the Intel FCLGA4-S heatsink suprisingly lightweight for its 134mm wingspan. Intel engineers apparently built the heatsink with a sub-550gram weight target in mind, and the stocky heatpipe was seen as a better option than a heavy solid copper core.

The 41mm diameter copper "thermal chamber" works along a similar principle as a heatpipe, using a working fluid under a vacuum. The low pressure causes the fluid to change states when heat is applied, allowing the vapour to rapidly conduct heat between hot and cold surfaces. A solid metal block by comparison would rely upon the metals conductive properties to move heat from the base and distribute it along the cylindrical walls to which the fins are soldered.

The Intel FCLGA4-S reference heatsink by comparison has relatively thin copper walls around the hollow chamber, as you can see in this cutaway image below. The walls are no more than 0.5-1mm thick, and a sintered metal wick is evidently used to return condensed working fluid back to the hot side. The copper base is surprisingly thin too, about 4mm. The net result is a really lightweight heatsink for its thermal performance capabilities.

http://www.frostytech.com/articlevie...articleID=2278

Finished my own tests this week with this Intel monster, very loud unit.