I just bought a new ibook and had apple upgrade the ram to a total of 768 for me. Well the stick they used was a 512 pc 2700 stick, I know the ibook takes pc 2100 though. Interestingly enough, the ibook sees the 512 ram as pc 2700 and the sodered motherboard ram as pc 2100. This is fine right? I uploaded an attachment called picture 2 to help explain what i mean.