Hate to be the hardware nerd here but speed has jack crap to do with anything. It's all about floating point and process's a second. This is becoming more and more apparent as Intel keeps upping there Ghz speeds with out raising there floating point performance by much. AMD on the other hand keeps uping there floating point performance while not effecting there Ghz rating much. Thus a 2.2Ghz P4 performs roughly the same as the new AMD 1900+(1.7Ghz) proc. Floating point operations per second has a huge effect on rendering since floating point operations are the type of math used to compute all the factors in a render. And as die hard an x86 PC user as I am I can't help but look at the hard facts that the Apple/MAC processors blow PC floating point numbers away.