I can't speak for the DDR RAM, but I know in the old PC-100 RAM Macs, you could use PC-133 and the logic board would dumb it down to PC-100. As far as the cost is concerned, I don't think RAM speed makes much of a difference, so I would go with the cheapest. Make sure it's from a reputable company and has a lifetime warranty. Nate -------------- Original message ---------------------- From: Aaron <macuser at aarons.fastmail.fm> > I need more RAM for my G4 Dual 867 MDD, which presently has one 512MB PC2100 > stick in it. (It came with two, but I took out a bad one and can't remember > where I put it so I can exchange it! <:-| ) >