PC World writes:
"Reader Dan wrote in for advice about upgrading to a new white MacBook. He found himself puzzled when it came to the memory situation in low-end model, especially vis-a-vis its aluminum counterparts:
As you probably know, the white version comes with 2 GB of 667 MHz DDR2 RAM. The Aluminum version comes with 2 GB of 1066 MHz DDR3 RAM. Both have a 1066 MHz front side or front system bus... all I know is it has the abbreviation FSB. My question, which I've posed to crucial.com, but they didn't know, and Apple, ditto (amazingly...), was whether I could take out the 2 GB of RAM in the whitebook and upgrade it to, not only to 4 GB, but also in speed.
Well, wonder no more. You're going to need to stick with the older DDR2, simply because DDR3 RAM isn't designed to be backward compatible. In fact, it's even possible you'll damage the slot by using the newer RAM, so we'd suggest you not try it, lest you end up sadder than the average panda. "