I've had my 4,1 8-core 2.66GHz MP for over three years now and I managed to find a pair of used Xeon w5590 for relatively cheap. I've been reading through Anandtech's article on their experience performing the CPU swap, as well as over on the MacObserver, and Tutor's thread here on Maximizing CPU performance. The processors are on their way and I went and ordered both some Arctic Silver MX-4 as well as a pack of 2mm thermal pads from eBay(coming from China, I believe). I'm aware of the non lidded processors Apple was using for this particular model, but I was wondering whether there was any consensus of whether to use the thermal compound or thermal pad, or even using both? I'll probably opt for the use of washers and I thought I read in a post from either Tutor or Gugucom that the clearance added by the IHS was approx 1.8mm.