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Power Management on MacBook

August 17, 2011

A user with a MacBook Air (SSD but not the very latest model) had his battery run down while the machine was in sleep. Lotus Notes was open and his local mail replica got corrupted. This lead me to an interesting investigation of sleep options in OS X.

First terminology: Apple uses sleep to mean the same as sleep or suspend in the Windows laptop world. But they use “safe sleep” to mean hibernate. As I understand it sleep holds the current contents of RAM to allow immediate resume, but requires power. Safe sleep writes the current contents of RAM to disk/SSD. Power can then be removed but it takes longer to restart.

My MacBook users are mostly migrating from Lenovo ThinkPads which have very granular power management. This includes the ability to set a delay for sleep and a longer delay for hibernate. This pretty much prevents the battery running down while in sleep mode.

There seems to be no equivalent on the MacBook Air, although I thought I remembered similar granular controls on an older MacBook Pro.

There also seems to be no standard way to manage the “safe sleep” function. I’ve been told it’s always used on the SSD MacBook Air, but our experience doesn’t bear that out. There seems to be no native way in the OS to invoke the safe sleep function in OS X 10.6 and later. There is a third-party Dashboard widget to invoke it, but not on a timer.

I’ve seen very little on this. Based on the mobile users I’ve worked with I would have thought it to be a hotter topic.

Please share your thoughts and insights.



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  1. Anonymous permalink

    look at

    details a way to set sleep to hibernation instead of powered hibernation


  2. David Schaffer permalink

    Thanks. I really didn’t want to change the default sleep behavior, but we may experiment to see if it’s fast enough with the solid state drives.


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