Before you all jump on me, I know this is high-end stuff. However, it explains memory very well.
The thing to note is, the memory timings don't mean squat with the AMD 64 processors, because the memory controler is on the die. Therefore, the memory is communicating directly with the processor and not with the controler on the North Bridge.
Please see this area especially:
The basic understanding (An AMD Athlon XP3200+ Barton 2.2Ghz 200Mhz FSB 32bit CPU)