Question : Problem: Memory Speed - Performance difference

Hi,
My supplier accidently sent me 2 modules of 1GB 266 MHz Ram instead of 400 MHz.

Although the 266 modules will work, they will not be as fast as the 400's.  My question is how noticeable will the performance loss be?

Answer : Problem: Memory Speed - Performance difference

Actually I'd hardly call the difference negligable.   IF your system will utilize DDR400 at full speed, the difference is in fact quite noticeable.   But if your CPU won't use the memory at full speed, it may not make any difference at all ==> DDR400 is fully downward compatible with lower speed memory, so if the system bus is a 133MHz bus then even with DDR400 you'll only get DDR266 performance.

Download and install Everest Home Edition [http://www.majorgeeks.com/download4181.html ].
Run it and look at the Motherboard - Motherboard display (Yes, it's the "Motherboard" selection under the "Motherboard" area).   See what the Real Clock is for your Front Side Bus.   If it's 200MHz then your system will fully utilize DDR400 ... and I'd swap the memory for what you should have received.   If it's 133MHz then the memory won't run any faster even if you get DDR400.   If it's 167MHz (it may display as either 166 or 167 in this case) then the memory would run at DDR333 speeds if you got faster modules.

In any event, your memory subsystem will run 50% faster if you have a 200MHz bus, and 25% faster if you have a 167MHz bus if you swap the DDR266 modules for DDR400.   And I can assure you that 50% faster memory makes the system "feel" much more responsive.