I just finished importing some AVCHD movies into iMovie, and my MBP became unresponsive. I opened up Activity Monitor when it was responsive again, and it looks like it ran out of RAM and started swapping stuff to the disk. I have 6gb of RAM, but apparently 280mb had to be swapped out. Why does the "Active" RAM add up to so much more than what is apparently in use? The wired RAM is less than the total real RAM, but active RAM is much more than the total real RAM. Why doesn't OS X dump "inactive" RAM? This page http://support.apple.com/kb/HT1342 defines inactive RAM as: "This information in memory is not actively being used. If your Mac needs to access this information, it will not have to load it from the slower hard disk." To me that implies that inactive RAM is the cache of recently used but closed programs that are kept in RAM to make them start faster next time. Why is this swapped to the disk when more RAM is called for? Shouldn't it be cleared out without saving it since it is not needed any more? I had this problem when I used to run VMWare Fusion with 4gb, and I haven't had any trouble running 6gb until now. Does iMovie really take that much RAM while it is importing movies?