What Happens When I Run a System with 4 DIMMs Filled?
What happens when you have all 4 DIMMS populated with RAM? In many cases, your memory clock will drop to the second highest clock speed (provided the memory was able to run at the highest supported clock speed natively). Just look at any older motherboard manual for evidence of this.
With respect to the Athlon64 with on-die memory controlers, those running with "Venice/SanDiego" cores (or newer) will be able to run with all DIMM slots populated at the full speed. With the exception of Athlon64-based processors (i.e., on-die memory controllers), this isnt a concrete rule in that some memory controllers will only drop the speed depending on the type of DDR (and i would imagine DDR2) memory installed (i.e., double sided or single sided).
Generally double-sided (DS) memory is a bit more finicky than single-sided (SS) meaning DS memory will tend to downclock (i.e., 4 sticks of PC3200 will run at PC2700). How do servers, which require craploads of memory ... deal with this? They [generally] use something called Registered Memory which, to simply state, improves signal stability (thus allowing the memory to run at the higher clock)
