iMac late 2013 does not have "Computer sleep" setting in Energy Saver prefs

Click on the Restore Defaults button and see if that restores the settings. May require a restart.

Also try it from a different account.

Looks like you may not be alone with this. I agree, it makes no sense.

https://discussions.apple.com/thread/5393978?answerId=23242759022#23242759022

http://forums.macrumors.com/showthread.php?t=1653886

The computer sleep setting is removed on the new Haswell processor Mac's.

Difficult to get an exact reason but basically the new chip automatically goes into low power states that for all intents and purposes does what the sleep setting did but on its own.

I don't know the answer to this, and I'm not finding any Apple article, but you might be able to find out by entering the following in Terminal (in Utilties.) At least the results may be interesting.

pmset -g

This will give you the current energy saver settings. Try it with "Prevent...." both checked and then unchecked.

This is the output from mine, just to give you an idea what to expect. My computer sleep is set to an hour and a half, and display sleep 4 minutes. Disk sleep 0 means the drive isn't allowed to sleep.

Active Profiles:

AC Power -1*

Currently in use:

hibernatemode 0

halfdim 0

womp 0

sleep 90

powerbutton 1

disksleep 0

hibernatefile /var/vm/sleepimage

ttyskeepawake 1

autorestart 0

displaysleep 4

It appears that the chip manages the power states itself. Again getting exact information on this is a pain and I'm really surprised (well maybe not so surprised) that Apple hasn't said anything about this. You'd think if they make such a drastic change to the system and to the Energy Savings pane of System Preferences there would be something.

From http://www.itpro.co.uk/desktop-hardware/19655/intel-haswell-release-date-and-spe cs-revealed#ixzz2iJsWa73p

Haswell chips will have 3 power states, compared to two in its predecessor, Ivy Bridge. These will be Active, Sleep, and Active Idle. Intel claims the advanced power saving will help give it at least 20x power consumption improvement over third generation chips.

It appears that the CPU will put itself to sleep if it is inactive for so many cycles. In a way this makes sense, the old method of telling the system to sleep after so many minutes is really very imprecise.

The only reason not to put the system to sleep as soon as it is idle is that it takes some amount of time to wake-up. So the lag would be annoying if it happened each time the system was idle. With the Haswell chip (as near as I can make out) wake-up is almost instantaneous. So there is no lag going from sleep to running. With no lag then it becomes feasible to put the CPU to sleep sooner and more often.

Again there is nothing I can point you to that states this it's what I've pieced together from various sources. In any case the missing setting in System Preferences is not an error so I guess you'll get to experience fist hand how this all works. Post back with your observations, it will be interesting to hear what you think.

regards

Bruce Kieffer wrote:

So do you think that since the chip has a low power mode, then checking "Prevent computer from sleeping when display is off" might be close to the same energy use as sleeping?

Just saw this.

You know I'm not sure, giving my interpretation of the Haswell chip, just want this setting does now. If the chip manages its own power states then I don't see the use of this setting unless this refers to things like disk and network.

I think you've got some experimenting to do 😀

regards

Not sure I follow. Are you saying after the upgrade the system doesn;t sleep at all or that another setting is missing or…?

Are you refering to the display? Or id the Computer Sleep slider back in System Preferences?