i was planning to get some more ram for my Powerbook 1.67 and Cube. if i were to buy ram, do i have to purchase it in pairs? like if i wanted 512mb's, do i have to buy 2 x 256mb chips? in my pb, i have 512mb and wanted to upgrade another gig - so i just going to buy a 1 gig stick since i only have 2 slots. and for my cube, i have 3 slots, 2 x 64mb and 1 x 128mb - so i was planning on taking out a 64mb and replacing it with a 256mb. sorry for the retarded question.