I have a 512 stick of pc2700 from my imac G4. I have put it in my 1ghz Powerbook G4, 12incher. The "about this mac" section shows 768, but nothings seems to run faster, I have 20gigs free on my HD, and iphoto, idvd all seems to respond the same... I think the powerbook uses pc2100? Does it step down and just work? any help would be great!