USB warnings on wake up

Discussion in 'OS X Mountain Lion (10.8)' started by digitalfailure, Feb 5, 2013.

  1. digitalfailure macrumors regular

    Sep 24, 2012
    Does anyone else's new iMac (2012 27") bring up a warning box when the machine wakes from sleep if a device is left plugged in?

    I opted for the wired keyboard as the usb ports allow me to conveniently charge my 4s while I work, but I've had a warning dialogue tell me that a USB device is drawing too much power and the USB has been shut down.

    If the machine is awake, I can plug my phone in and it's ok so it seems to be something associated with going to sleep.

    Anyone ?????
  2. defavantbop macrumors newbie

    Apr 4, 2013

    I'm seeing this too on a brand new iMac 27". It happens when the computer goes to sleep.

    The only relevant thread I've found online so far is
    but it's definitely out of date.

    You implied that you only have a wired Apple keyboard connected - is that correct? I have two other devices as well so I still need to try disconnecting them on sleep.

    One other detail: sometimes when I wake my iMac from sleep I simply press the space bar and I see a login window. Other times, the space bar does not work and I have to press the power button to wake it up. At this point it has some sort of progress bar at the bottom of the screen, before I can log in. Only in the LATTER scenario do I see this USB warning.

    Any further developments on your end?
  3. superriku11 macrumors member


    Jun 16, 2012
    United States
    That is your computer waking from Safe Sleep, somehow. As far as I knew, desktop models had the software capability, but the feature would never be natively activated.

    On laptops, it activates if your computer runs out of battery while in sleep. Then once recharged or plugged in, and booted, it restores the previous contents of RAM from the hard drive (it saves before it shuts down) and resumes execution.

    It's basically like Hibernation, in GNU/Linux systems, or Windows, if you are familiar with either.
  4. defavantbop macrumors newbie

    Apr 4, 2013

    Thanks, that helps. Led me in the right direction to find this:
    which says that the safe sleep is an energy compliance feature on these models and is only activated when wireless and USB activity is idle for 4 hours. Interesting because in fact my wireless connection was very bad during the time I most recently saw the symptom. Going to try turning off wireless AND unplugging the USBs to see this happen. I'm just crossing my fingers this isn't the logic board issue that I've seen mentioned.

Share This Page