There is a very good thread going Here regarding S.N.D.S..... Enjoy! 
I'm not sure why SNDS happens mostly on Intel CPUs, but I believe they also happen with TBred. From what I understand, AMDs fabs are completely automated. No humans are allowed in the fab and they work with microenviornmental chambers where inside the chamber where the chips are worked on can be a Class 1 enviornment while the cleanroom itself can be Class 10 or even Class 100. I believe that Intel still has factory workers working in the fab, and believe it or not, the biggest source of particles that cause critical defects are humans. Not only do we constantly shed a lot of skin, our bodies also carry ions that can get into the wafer and have a detrimental affect on such things as the capacitive abilities of the gate structure aka MOS Capacitor or can affect carrier mobility in the silicon itself.
