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Mountain Lion on iMac with no SSD - why is Power Nap forcing my computer to sleep?

I have an iMac purchased in mid-2011. It has no SSD. So why is it going to sleep when tasks are still running? If I'm encoding a video in HandBrake, downloading files in Firefox or Chrome, etc...the computer goes to sleep, despite the fact that it's still doing something. Why is this? If my iMac is not Power Nap capable, shouldn't it use the old method for determining whether or not to go to sleep? Why can't we choose between Power Nap and previously functioning sleep behavior?

iMac, OS X Mountain Lion (10.8.2)

Posted on Oct 31, 2012 2:05 PM

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10 replies

Oct 31, 2012 2:36 PM in response to mrbofus

First, your iMac doesn't have Power Nap. It's only available on recent macs that ship with SSDs only.


Future upgrades to 3rd party applications may be able to prevent the activation of the Sleep function when they're active. Unitl then, set your Mac so that it won't go to sleep, at least until you finish your extended tasks.


mende1 gave you sound advice, there's no reason for you to be snippy about it.

Oct 31, 2012 4:17 PM in response to Lanny

Quite the contrary. The first thing "mende1" said was, "If you don't use your computer, the computer could go to sleep." when I explicitly stated that the computer was going to sleep WHILE tasks were running. The issue was never about whether or not the computer would go to sleep if I wasn't using the computer.


Additionally, I am quite aware that my iMac does not have Power Nap. That's why my post title was explicitly stating that I have an iMac with no SSD.


My question is why users without SSDs are forced to use power settings for computers with SSDs. Under previous OS X iterations, if there was processor or disk activity, the computer wouldn't go to sleep since stuff was going on. It wasn't required for the application itself to let the OS know it was doing something. Since there are more Macs without SSDs than there are Macs with SSDs, it seems odd that we aren't at least given the option to use the non-Power Nap power settings. Or that the OS knows that there is no SSD so it's going to use the previous power settings that worked for decades prior.


I was hoping there might be someone out there who knows the ins and outs of Mountain Lion/Power Nap/Apple better than I that could provide an explanation or solution. Setting my Mac to not go to sleep on an application per-use basis defeats the purpose of having energy saver settings at all.

Oct 31, 2012 9:50 PM in response to Lanny

If I may ask, how do you know that the issue is with 3rd party applications?


And is the implication then that it has nothing to do with Power Nap? If so, then it becomes a more serious issue that affects even Power Nap capable Macs; why do any computers running Mountain Lion go to sleep when there is processor/disk activity ongoing?


If the issue is third-party applications not being updated, wouldn't it make more sense for Apple to give us the option of deciding which power saving scheme to use until those third-party applications are updated?


I'm just confused on why Apple would have made it so that computers would go to sleep even if there is processor/disk activity ongoing.

Nov 1, 2012 7:49 AM in response to mrbofus

If I may ask, how do you know that the issue is with 3rd party applications?

Well, you could do some research on the issue for yourself, or you could just ramble on about why you think Apple is responsible for developers not keeping up with changes to OSX.


Maybe this will help: http://forum.serviio.org/viewtopic.php?f=5&t=7791


Apple offers developers previews of their OSX upgrades months in advance so that they can update their softwares to function properly. Some developers do a better job on this than others.

Nov 1, 2012 9:58 AM in response to mrbofus

The computer shouldn't go to sleep while applications are active but obviously some programs are not well behaved. I've not used HandBrake in quite some time so I'm not sure if it plays nice with Mt Lion or not. I have seen Chrome fail to keep the computer aware during a download. I don't use FireFox.


While I can't help with the sleeping part of the problem, I can tell you that PowerNap has nothing to do with putting the computer to sleep. PowerNap determines whether a computer that's asleep can be minimally awakened to perform a limited number of functions including checking mail. So whatever your problem is, it isn't PowerNap related.

Nov 1, 2012 12:47 PM in response to Lanny

Lanny wrote:


Maybe this will help: http://forum.serviio.org/viewtopic.php?f=5&t=7791


I am unclear on how that will help. It is a link to a post from a user on a non-Apple website whose first and only post is about how this problem exists. And I assume if you're referring to the Apple Discussion thread that other post links to, you would have just posted that link instead.


If you intended to link to that other Apple Discussion thread, from that discussion thread, Apple told one user, "Apps need to use power assertions while engaged on activities that should not be interrupted and we are working to evangelize this." meaning that Apple realizes they haven't done a good job of letting developers know of this; and that was from October 18, 2012, nearly 3 months after Mountain Lion's release date and I believe nearly 8 months after the first developer preview. So by Apple's own admission they haven't done a good job regarding this issue.


However, that does explain why Mountain Lion is behaving the way it did. Both Apple and developers dropped the ball on this given that major apps (Firefox, Chrome, etc...) still don't implement Apple's new method of power saving.

Nov 1, 2012 12:50 PM in response to Lanny

Lanny wrote:

Well, you could do some research on the issue for yourself, or you could just ramble on about why you think Apple is responsible for developers not keeping up with changes to OSX.


Now who's being snippy? I guess it's OK for you to be snippy while telling other not to be? 🙂


And how is me posting on Apple's site NOT doing research? Your implication is that I'm not doing some research, but the mere fact that I have posted here is part of doing research, is it not?


And as my previous post shows, even Apple admits that they bear some responsibility for developers keeping up with changes to OS X, or at least this particular change.

Mountain Lion on iMac with no SSD - why is Power Nap forcing my computer to sleep?

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