hughyhunter :
I guess I'm having a hard time understanding memory/cpu speeds then. Why would a mobo manufacturer like ASUS allow memory compatibility to be DDR2 1200? If what you say is that you could go so much cheaper and slower with no performance loss.
The P5E says to use DDR2 1200. Why wouldnt you get the 1200 and why would you get 800 instead? Is that what you are saying?
I still believe this is all about marketing... and it filters down to end users/buyers thinking that higher numbers mean better when its not necessarily the case. I dont see anyone using a P4 3.6ghz over a e6600 at 2.40ghz do we? But the average users thinks wow 3.6ghz that higher than 2.4ghz so the P4 must be faster. Although recently this seems to have died off others have taken its place.
To my knowledge a C2D chip will not run lower than 1:1 FSB: DRAM however, testing done at increasing this ratio in favour of DRAM doesnt seem to improve numbers in real world apps a great deal(4:5, 2:3 and 1:2 are most popular). Hence why when overclocking generally people will keep this 1:1 ratio as not to have to OC the ram at all. As i said before 800 or 6400 DDR2 will quite happily get a Q6600 to 3.6ghz (400x9) without needing to OC the RAM, and to get a Q6600 to that speed your gunna need some serious cooling.
If you note on ASUS product page those boards that you suggest support DDR2 1200 actually have an * next to them, denoting that the chipset doesnt actually support this speed but they can get this by overclocking. So if we go out and buy some DDR2 1200 RAM and run it at STOCK the chipset on the motherboard is actually OCed to get the RAM to Stock this will increase power usage and therefore heat disipation.
Soon Intel will release there 1600FSB CPU's now this is getting closer to where we need some faster RAM at stock they will need 800mhz DDR2 to run... An overlcock on the CPU youd be happier with some 1066 or even 1200 RAM this is getting close to needing DDR3 then IMO as the DDR2 specification craps out at about 800/1066 according to WIKI
http://en.wikipedia.org/wiki/DDR2. When Intel release there new Nehalem parts we will see intergrated memory controller and the need for faster DDR3 by this stage it will be cheaper and lower latency (we hope). However, when intel do release this it means a chipset/socket change and your pretty little x38 board that supports DDR3 will be worthless.