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  1. #1

    Member Since
    Jan 23, 2007
    Clarification on OS X RAM usage
    I'm having trouble understanding how all my ram is being used. The applications running don't take up anywhere near 1 GB. Can anyone explain?

  2. #2

    mac57's Avatar
    Member Since
    Apr 29, 2006
    St. Somewhere
    iMac 27" 3.4 GHz, 256 GB SSD, 2 TB HDD, 8 GB RAM
    Here is the definition of the terms you see:

    Wired memory
    This is memory that applications or the system needs immediate access to, so it can't be cached to disk. It will vary depending on what applications you're using.

    Active memory
    This is memory that is actively being used.

    Inactive memory
    This memory is no longer being used and has been cached to disk. It'll remain in RAM until another application needs the space.

    Free memory
    This memory is not being used.

    The above is a copy 'n paste from a post I saw on these forums some time ago. I found it useful enough that I saved it off. Hats off to the author, who ever you were!

    In general, only your Active memory should be considered "in use" by your applications. I am guessing that the "wired" memory is likely mostly OS stuff, plus lower layer support stuff.

    Looked at this way, it does more or less add up.

    Does this help?
    My Macs: iMac 27" 3.4 GHz, Mac Pro 3.2 GHz, PowerMac G5 Quad 2.5 GHz, G4 Cube with 1.2 GHz Upgrade
    My iStuff: 64GB iPhone 5, 64GB iPad4, 30GB iPod Video, 16GB iPod Touch
    My OS': Mac OS X Lion, Mac OS X Snow Leopard, Mac OS X Tiger, Mac OS 9.2.2, openSUSE 10.3
    I was on the Mac-Forums honor roll for September 2007

  3. #3

    Member Since
    Jan 23, 2007
    Thanks for the post, very helpful.

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