All you should read this ...about AMD Athlon/Opteron processors ...
The memory connections are direct, glue-less, 184-pin DDR SDRAM channels directly connected to the chip. There is one DDR channel in Socket-754 and two DDR channels in Socket-939/940 (noting that 754+184=938, there are two, true, full, non-multiplexed DDR buses in the case of Socket-939/940). There are several advantages to this. One is the fact that memory speed no longer limits the performance of any other interconnect. In other words, the memory clock is its own, independent divider of the local CPU clock -- separate from all others, including I/O. Using DDR266/PC2100 (2.1 GBps/channel) instead of DDR400/PC3200 (3.2 GBps/channel) makes no impact on the CPU speed or HyperTransport clocks. And, it gets better.
Taken from this very interesting link ...http://www.samag.com/documents/s=9408/sam0411b/0411b.htm
Any comment now is really welcome.