I have a mac pro at home and a G5 at work. The Mac Pro has 3GB of RAM and the G5 has only 1GB of RAM. I use MenuMeters both at work and at home. When I boot the G5 and start working, it shows 260MB of RAM already being used by the System, Suitcase, Safari and Illustrator CS 2. However, at home when I boot up my computer, it shows 500MB already in use without opening any Apps at all!... what the? I don't have anything usual running in the background at home or at work. I run more dashboard widgets on the G5. I run 1 widget on the Mac Pro (Swap Usage Widget) Once I get a few things running on the Mac Pro like Safari, iChat, EyeTV and stuff, my RAM usage goes easily up into the 1GB area. The other thing would be is... does it know it can use more RAM when more RAM is there to use? Like, does it see that I have 3GB and gives Applications an extra amount so they run smoother or something?