[Beowulf] Opteron downrates DDR400 to DDR333 performance?

[NazarioJose at JohnDeere.com]

Hello, computer gurus -
do any of you know if the AMD Opteron downrates the PC3200 400 MHz DIMMS 
(DDR400) to 333 MHz (DDR333) performance  when the system has more that 2 
Gbytes of memory installed?

i was told that when an opteron socke has more that 2GBytes of memory, then 
the cpu will automatically downrate the memory rate to an equivalence of 
DDR333 memory.

Thank you for your time.
Jose.