I've noticed some strange memory consumption on Intel Macs, compared to PPC Macs. I thought that my Mac mini (1GB RAM) at work was only affected, but when I replaced my PowerBook G4 (640MB RAM) with a MacBook (1GB RAM) I also noticed this behaviour. Basically it appears as though half of the memory is not being used properly, as evidenced by the screenshot of Activity Monitor. Usually there is ~10MB of free memory, a virtual machine in Parallels was just shut down in the screenshot. I actually experience a performance hit when running less applications than I did on the PowerBook, which had closer to half the memory of the MacBook. Is this expected behaviour? The private memory looks correct, but iterating through the memory output of /bin/ps adds up to nowhere near 1GB.