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Deep Sleep

posted Jan 10, 2011, 2:01 PM by Michael Schollmeyer   [ updated Jan 11, 2011, 1:05 AM ]
On a Windows computer, you have 3 shutdown options:
  • Shutdown will terminate the operating system and turn off power. Restart takes time.
  • Suspend halts the processor and peripherals but keeps RAM alive. Restart is fast, but the computer consumes power.
  • Hibernate copies all RAM to the page file and then switches off. Restart is faster than Shutdown. 

On a Mac computer, things are different. With default settings enabled, the computer will suspend to RAM but also flush the RAM to disk when suspending. When the battery dies while suspended, you can recover from disk.


Another difference I noticed between my Sony and my MacBook is that suspending the Sony for one night would almost drain the battery. Suspend on this machine is only useful when you are planning to pause for a couple of hours. 

Thus, suspend to RAM on a MacBook is good in most situations. However, when you know you will not use your computer for some time, you might want to Hibernate explicitly. 

You can find out the mode your Mac uses with the following command:


pmset -g | grep hibernatemode


You can change the mode your Mac uses with the command:


pmset -a hibernatemode <new mode>


Now you don't want to open a shell to suspend your machine. And this is the point where Deep Sleep helps. It is a dashboard widget that you can use to shutdown your computer using a specific mode.
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