Well, on almost all recent Intel chipsets, Intel implemented a memory speed multiplier setting into the chipset. And with CPU multipliers locked, that leaves only raising the FSB speed as a mean to overclock. With a FSB:RAM ratio, the lowest of which is 1:1, that means that you also raise the memory clock speed. Which generally means that you have to purchase faster memory to overclock. Then again, most good DDR2-800 memory will overclock to 450Mhz without an issue, when you raise the RAM voltage a tad.