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What's causing iMac to seemingly randomly come out of sleep mode?

Ever since I first got my Mavericks iMac, which was about a year ago now, and set it up, it's had the annoying habit of coming out of Sleep mode occasionally all by itself. When it does so the screen remains black but the iMac re-establishes its Ethernet connection with the router. To date, I've never found a convincing explanation for this. I find it somewhat concerning. But possibly the way it's working is correct? So, I'm wondering if anyone else has observed this.


There are several forms of Sleep mode, I gather (I've read Apple's notes on Sleep mode). This is the one where, having finished a session on the Mac, I select the Apple menu and, rather than clicking on Shut Down or Restart, I click Sleep. This blanks the screen and, as I understand it, leaves the machine in an activated but low-power condition. It also, after a delay of about 7 secs, automatically disconnects from the Ethernet interface (wired, in this case) with the router. This is observed by means of the Ethernet port indicator on the router. To resume work on the machine, a press of a keyboard key or a click of the mouse is all that's needed, and the Ethernet connection then also automatically resumes.


It all works okay, apart from the Mac from time to time coming out of sleep mode all by itself, including re-establishing the Ethernet connection - but with the screen still blank. As an on-the-spot remedy I then use the mouse to bring the Mac fully out of sleep, ie. I bring the screen back, then put it back to sleep again. This oddity happens completely randomly (or so it seems), about twice a week on average.


I've analysed all my power, UPS and screensaver settings and I use no remote services, but have thus far failed to pinpoint the cause. I've also read Apple's published notes on Sleep mode but none of their suggested possible causes seem to fit.


The only explanation I can come up with is that perhaps from time to time the Mac decides to do a backup, despite being in the Sleep state. I run Time Machine, backing up to an external USB-connected SSD. But if that's correct and valid, why should it also re-activate the Ethernet connection to the router?


Can anyone come up with a better explanation?

iMac (27-inch, Late 2013), OS X Mavericks (10.9.2)

Posted on Feb 2, 2015 8:33 AM

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6 replies

Feb 2, 2015 3:09 PM in response to BobHarris

Those links are useful, but the problem is that I have never ever selected 'Enable Power Nap' in my iMac's Energy Saver settings. It's only ever been de-selected, and currently that's still the state that that setting is in. Therefore in theory my iMac should not be performing any of the functions mentioned in Apple's 'OSX: About Power Nap'.


And just in case anyone might be thinking that I've acquired a trojan and it's calling home, I'd think that highly unlikely indeed, because (a) this behaviour was there from Day One, and due to discovering other bugs, a few weeks later I even completely wiped the hard drive and reinstalled Mavericks as an Internet Recovery, and (b) because I've always been careful about security and never visit untrustworthy websites or click on links in phishing e-mails. I don't use iCloud and all possible interrupting features of Contacts, Calendar, Notes, etc are disabled, as I've no use for them.


So, perhaps you can now understand why I'm both annoyed and baffled by my iMac coming out of Sleep mode by itself, when the Apple literature indicates that it shouldn't.

Feb 2, 2015 3:18 PM in response to carefulowner

Start reviewing the Applications -> Utilities -> Console log entries.


Do you happen to have System Preferences -> Energy Saver -> Wake for network access enabled?

AND do you have an Apple TV or Airport Extreme or Airport Express or Time Capsule?

If so, then it is possible that other devices on your network are trying to access your iMac and the Sleep Proxy is sending a wakeup packet to your iMac.

NOTE: It is possible that there are other non-Apple network devices that could provide Sleep Proxy services.

<About Wake on Demand and Bonjour Sleep Proxy - Apple Support>

<http://en.wikipedia.org/wiki/Bonjour_Sleep_Proxy>

Feb 3, 2015 1:49 AM in response to BobHarris

Bob,


I think I was a little dismissive of "OSX: About Power Nap", but yesterday I made a printout of it and read it a bit more carefully, and I think I may have found the reason why my iMac's doing what it's doing. Although I've never had Power Nap enabled, it looks as though my particular iMac falls into a category where Apple has enabled it regardless. Read these two excerpts from the article, for example:


Turning Power Nap on or off

Desktops -

On desktop computers you can enable Power Nap under Apple menu>System Preferences>Energy Saver. Place a checkmark next to Enable Power Nap to turn it on, or remove the checkmark to turn it off. Note: Power Nap is on by default only on Desktops that use Flash Storage (not including Fusion Drive systems).


Well, my iMac is a machine with Flash as the hard drive, and it doesn't use Fusion Drive. So, if I understand this correctly, it seems that Apple has permanently enabled Power Nap on my machine - even though they still provide the setting with which to turn it on and off. I mean, there's not even a greyed-out checkmark showing there, in the Energy Saver setting.


If you look also at the section in the article named "How often does Power Nap check for updates or backup?", it includes any updates or messages required for Mail, Notes, but it also includes several features I specifically don't use and have effectively disabled. Apparently, during Power Nap, Time Machine backups are attempted (in my case, the backup drive is a USB-connected SSD, which is powered directly off the USB connection). Software updates and Mac Store downloads are also attempted, but these won't take place because I've disabled them from happening automatically; I always do my updates manually and there's never been any evidence that I've ever missed any.


Whilst I'm happy to have TM backups happening while my iMac's in Sleep mode, I'm not so happy about the attempts that are made to get Mail messages and any pending updates. Clearly, this is why I'm finding that the Ethernet connection to the router, and thence to the Web, has occasionally re-established 'by itself'. I suspect that what happens is that the connection is made but then possibly it hangs because I've disabled that particular app or group of apps from getting updates automatically.


I'm finding that, depending on exactly how I read and therefore interpret it, the article also suggests that some apps, such as Mail, have to be left open when you put the machine into Sleep mode, before any such covert updates can happen. Well, in my case I always ensure that I close every app before I put the iMac into Sleep, and I'm not sure whether attempts to get new mail will therefore still then occur. Incidentally, I don't use iCloud and I don't use webmail. The form of mail I use (with Apple Mail as the client) is pop e-mail, so only the ISP's mail servers are involved in the fetching/despatching of my mail.


I find it rather odd that Apple has permanently set Power Nap on a machine that's always plugged into AC power. And that being so, it's counter to the way in which I prefer to use my iMac. Of course, I can avoid all of this by doing a Shut Down instead, after each session on the machine, but the Sleep mode has some definite advantages over that. Do you agree that Apple's decision to make my particular iMac use permanent power nap during Sleep is a bit crazy?


Oh, and I don't have, anywhere, any 'wake on ..' settings left in their enabled states. For instance, Wake on LAN or anything equivalent to that, is turned off.

Feb 3, 2015 6:07 AM in response to carefulowner

Do you agree that Apple's decision to make my particular iMac use permanent power nap during Sleep is a bit crazy?

I do not have a Mac that supports Power Nap, so I do not have any experience with it, nor can I experiment.


To me it is "Noise" and after all the years I've put up with other computer oddities (I started in the early '70's working for UNIVAC), I would not get upset about how Apple has implemented Power Nap.


You can provide feedback to Apple via

<http://www.apple.com/feedback>


And if you think it is a bug, you can use BugReporter

<http://bugreporter.apple.com>

Free ADC (Apple Developer Connection) account needed for BugReporter.

Anyone can get a free account at:

https://developer.apple.com/register/index.action

Feb 4, 2015 6:11 AM in response to BobHarris

Yeh, I kinda agree with you. It looks like I'm stuck with permanent power nap when my machine's in Sleep mode, and I'll just have to learn to live with its unrequired effects (in my case).


From time to time I do send comments about various aspects of Mavericks to Apple via 'feedback'. I'll do so now with this. But I somehow can't seem them doing anything about it, as I'd hazard that I'm a little unusual in not opting for features such as automatic updating, iCloud, and so on.


Anyway, many thanks for responding to my question and giving me those links. Had I not seen and looked closely at the first of those, I'd have probably never discovered the reason why my iMac works in the way it does. When I read earlier Apple articles on Power Nap, nothing was mentioned in them about specific iMacs, and especially those using internal Flash drives.

What's causing iMac to seemingly randomly come out of sleep mode?

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