Originally Posted by JogaBonito1502
That's not what I said. I know it's a dual core, however desktops C2D (Core 2 Duo) are quad-pumped. All quad-pumped means is that your processor can access the memory sub system 4 times a cycle. Therefore systems that are quad-pumped have their FSB Clock divided by 4 when accessing memory. Because DDR is Dual Data Rate, you divide the actual speed by 2 to get the data rate.
(The RAM and the CPU speed ratio must be 1:1 in order for the system to be stable. When I said that Mobile C2D were dual pumped was because I was ignorant of what the pumps actually were. When I looked up on it, I figured out that dual and single pumps are really old. Most of the processors today are quad-pumped.)
So in your case:
800MHz FSB Quad-pumped = 200MHz per pump.
To get your RAM to match you would need something that does 200MHz per pump. Because modern single rate memory (not SDRAM) did 2 "pumps" a cycle they had to create Double Data Rate memory. In your case 400MHz will do 2 200MHz pump, and since it's Double Data Rate, it will double the data rate (which does 2 pumps a cycle) thus doing 4 200MHz pumps and matching the CPU FSB perfectly. With that being said, you won't need anything higher than a DDR2 400MHz RAM.
the bolded isn't necessarily true, it doesn't have
to be a 1:1 ratio, some people (including myself) just find that their system runs better or more to their liking with it that way, you can run high speed memory at it's rated speed even if it's speed is higher than the FSB, but it's debatable whether or not you will see a performance boost, I don't really see one so I underclock my memory to get the 1:1 ratio but I don't have to do that to get it to work...