I have up and running a 3.3Ghz MacPro1,1 "OctoCore". Originally with 2X 5160's, I came into two X5350's (2.66/1066). With the BSEL and VID mods the FSB was raised to 1333, which forced the CPU to 3.3Ghz. Initially unstable, a VID was performed raising the Vcore eventually to 1.425 which proved satisfactory. Heat issues prevented stressing the machine causing panics within 1 minute of Handbrake encoding being started, though the computer was stable for web browsing, email, etc. A cooling system adapted from PC water cooling systems was successful. This was tied into a home-built geothermal ground loop to prevent heat buildup in the office. A proof of concept video has been placed on YouTube at: http://www.youtube.com/watch?v=gCz5pqbvEwc Thank You.