I'm planning to get the ASUS P5KC mobo with 1333 FSB. I read somewhere that 667 DDR2 in Dual Channel mode will give me the maximum memory bandwidth for that board, i.e. using DDR2 800 or 1200 in Dual Channel mode would be no faster.

Is this correct?
Thanks in advance.

This really will depend on the money you want to spend… higher MHZ ram with lower latency will be faster, and more expensive.

Example:
1gig 667 ddr2 with 4-4-4-12
1gig 800 ddr2 with 4-4-4-12
The 800 is faster.
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1gig 667 ddr2 with 4-4-4-12
1gig 800 ddr2 with 5-5-5-24
I would think the 667 is faster as it has tighter timings.

I would find yourself some Dual-channel DDR2 800/1066 with good timings, CL4 or better.

Actually the 800 5-5-5-!18! woudl be faster.

would never be 24.

667 ddr2 with 4-4-4-12
800 ddr2 with 5-5-5-15
800 ddr2 with 4-4-4-12
1066 ddr2 with 5-5-5-15
1066 ddr2 with 4-4-4-15
1150 ddr2 with 5-5-5-18 <- depends on mobo