Basically, how does the system save every state in the workspace (windows, desktops, open programs etc) when you do a restart ? Does that affect the efficiency of the software in the long run ?

For example, when I do a restart in windows I know that the laptop restarts completely. Resetting the hardware/software states etc. However, a restart on the macbook pro is like a hibernation in windows, how do they do that ? Is the power to the RAM not cut in the restart process ?


There seems to be a clash in responses down there .. Is the image cleared on reboot or not ?


When you restart a Mac it is the same as restarting a Windows machine as far as clearing out the contents of RAM. The difference is when you log in the state of all of the running apps is saved when they quit so they open to the same place they were. This is dependent on how well the application is written. Apps where less attention was paid to saving state don't come back to exactly where they were. Apple apps are very good at this so it appears as if they were never quit.


One trick that OSX uses to make it seem like it's rebooting and restoring the state very quickly is that it's actually showing you a picture of your desktop for the first few seconds after you boot. You can't actually interact with your computer until all the programs load, and on a Mac with slow storage (like my Mac Mini with a pokey 5200 RPM hard drive), there's a very noticeable period when the computer looks ready to use but is not.


The "sleep image" takes a a snapshot of the state of your computer at all times, and stores it in a file the size of your actual ram. During Boot or restart, this image is searched for for restore, unless you uncheck restore windows when you restart or shut down.

Its just another process in the booting phases.

  • Wrong answer. The sleep image is cleared on “reboot". Other answers are correct. What you are talking about is hibernation.
    – duci9y
    Oct 24 '12 at 6:11
  • The sleep image is not cleared on reboot since Lion. In previous builds yes. Oct 25 '12 at 13:13
  • 1
    That defeats the whole purpose of a sleep image. If it is not cleared, it would be storing stale data. It is, indeed, recreated on every boot.
    – duci9y
    Oct 25 '12 at 13:46
  • Ok, whatever you say. I, however, just completed my third recertification with Apple. This was widely discussed. Oct 25 '12 at 15:58
  • If you are certified then link to the Apple resource documenting this. Oct 28 '12 at 18:23

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