I would like to know more about this topic (AMD64
performance) too
Ron Kuper from Cakewalk has put up a whitepaper on the subject, the average gains are
around 30% for a simple recompile to 64bit. theres twice as many general-purpose registers
in 64bit mode, but that is offset slightly by increased memory bandwidth used for pointers
etc.. heres the link:
http://www.cakewalk.com/x64/whitepaper.asp