Is HT/RAM 1:1 relation that good? (AMD ONLY)

Hi people, this is my first new topic here
I wanted to ask something: I saw a guy in this forum that says the memory is holding him back (at 325/650 MHz) in his overclock of an Opteron 144 @ 2928 mhz "with slighly increased voltage".
I guess the Opteron would do a lot more with higher voltages and async RAM.
I know that in Socket A/775 and older sistems it´s very important to keep 1:1 FSB/RAM relation in order to avoid asyncrony and then causing problems with the chipset (as seen with the KT400 @ FSB333/RAM400) but what happens in sistems that have an on-processor memory controller?
Stock, the K8 has more HT bandwith that the one who has with RAM (6400/3200 MB/s for S754 and 8000/6400 for 939/940) and although the HT is a QDR bus (200x4 x 2 lanes -in/out) the memory is a DDR bus 8O
Isn´t it an asyncrony already?
Sorry about the long post, I don´t speak english and I have some troubles making myself understood. Thanks!