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Question: Power Management Confusion - autopoweroff vs standby vs hibernatemode

Good evening everyone,

Acording to manual autopoweroff sets whether to go into low-power sleep or standby mode. But what's the difference?

Can someone explain difference between low-power sleep and standby mode please?

My iMac have set by default both standby 1 and autopoweroff 1 with standbydealy 10800 and autopoweroffdelay 28800. I'd like to know which state exactly applies when and which of them actually takes priority?

How does hibernatemode go with all that above together???

I was thinking when my iMac (probably like other desktops) have hibernatemode set to 0 it should fall just into the plain sleep where no memory supposed to be written to disk. But what surprise, if I check timestamp of my /var/vm/sleepimage file it's pretty current with file size over 2 GB.

The point is, I don't wanna bother SSD portion of my Fusion Drive with recurrent sleepimage file writing and I don't mind keep my memory powered all the time during simple plain sleep, but how can I configure this with 'pmset' properly?

Thank you guys for explanation and maybe advice, have good night, bye.


iMac with Retina 5K display, macOS High Sierra (10.13.3), iMac17,1 Fusion Drive

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Mar 12, 2018 5:28 PM in response to Manolis_from_Prague In response to Manolis_from_Prague

Standby Mode

For Mac computers that start up from an internal SSD, macOS includes a deep sleep mode known as Standby Mode.

Mac computers manufactured in 2013 or later enter standby after being in sleep mode for three hours. Earlier models enter standby after just over an hour of sleep. During standby, the state of your session is saved to flash storage (SSD). Then, the power turns off to some hardware systems such as RAM and USB buses.

Standby extends how long a notebook computer can stay asleep on battery power. A notebook with a fully charged battery can remain in standby for up to thirty days without being plugged in to power.

Safe Sleep

macOS also includes a deep sleep mode known as Safe Sleep. Your Mac might enter Safe Sleep if your battery begins to run low, or your computer is left idle for a long time.

Safe Sleep copies the contents of memory to your startup drive and powers down the computer, allowing you to pick up where you left off without losing your work.

To wake your Mac from Safe Sleep, press its power button. If you use a Mac notebook and its battery is low, connect the AC adapter first.

When you wake your computer from safe sleep, a progress indicator appears. This indicates that the previously stored contents of memory are being read from the startup disk and copied back into RAM.

Safe Sleep:

Standby Mode: About standby on your Mac - Apple Support

Mar 12, 2018 5:28 PM

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Question: Power Management Confusion - autopoweroff vs standby vs hibernatemode