Dual Channel RAM on an Athlon XP System

Yeah, but it does pump up the performance gain with a AMD 64 system.

[Dragon]

theoritically, but doesnt it depend mainly on the bandwidth of you ram/mobo?

Yup, that's why it's best to have a processor that has dual channel memory controllers. The XP processors don't. The DC memory channel was after their reign, which is where the new 64 processors jump in.