Thermalright SP-94 Heatsink
"Now we move on to the installation. As noted previously, the installation for the SP-94 is a little more involved than the SLK-947U. To install the SP-94, you must first remove the P4 retention bracket that most traditional P4 heatsinks use. With only a 20g increase in weight from the SLK-947U, I was really surprised it would require such a robust mounting system."
Direct Link: http://www.ocia.net/reviews/thermalr...ght-sp94.shtml