I just finished the upgrade from a 8 core 2,26 to a 12core 2.66. While this is not an easy upgrade, it was easier as expected. The hardest part to me was to reconnect the fan controller. All in all I took my time and spend around 3 hours. I used this guide https://web.archive.org/web/2013102...Photography/2013/07/08/mac-pro-2009-part-tbd/ Here are some things that I believe can be helpful if you decide to do this upgrade. I used 2,5mm cooling pads and no washers. When you tighten the bolts of the heatsinks, usually you need around 4 turns with the new cpu! Nonetheless use your brain - if you feel 3,5 turns are enough you might be right. When you clip the frame of the fan controller, it might be easier to reconnect when you don't clip off the the smaller parts. That way you have some "grip" when plugging it in again. My "technique" for reconnecting the fan controller was different though. I installed the cpu after the fan controller was connected. So first I clipped off the frame like shown in the pindelski tutorial. Once free from the cage, I reconnected the fan controller but didn't place the heatsinks. Instead I hold the heatsink in one hand and installed the cpu with the other. Once the cpu was in place I installed the heatsink and tightened the bolts from the heatsink as described above. If you do this upgrade, take your time and keep calm. Like I said earlier use common sense and your brain. Try to stay away from touching the pins or any other sensitive parts - it might not destroy them, but why risk it. Make sure you install the cpu correctly and don't overtighten the bolts. This upgrade is absolutely doable if you focus and concentrate.