I am hoping
BurntKooshie will jump in and give a more-detailed explaination of that. Basically, the G4 has registers that are wide enough to bit-slice the keys, whatever that means.

The Athlon family holds a noticable edge per MHz over the Intel P2 and P3 family. The real shocker is the Pentium4, which cracks RC5-64 at a rate approximately equal to... a Celeron 500MHz :Q Hopefully they will have a revised cracking routine ("core"

for the Pentium4 that will allow it to perform well. When it was first talked about, we were all hoping that the double-pumped ALU would result in some very fast cracking... and maybe it still will, once an optomized core has been written for it.