Crucial's memory program says I need this 200-pin SODIMM, DDR2 PC2-6400 256Meg x 64 is the 256x64 important for it to work on a mac? For the windows machines to the best of my knowledge it makes no difference what so ever. Do I need to be concerned about the 256x64? 128x8 seems to be another popular memory configuration. I'm looking at getting 2 2GB sticks to fill it up at 4GB.