Mountain Lion can’t Wake Up from Slumber

Sleeping Mountain LionIf your primary machine is a Mac laptop and it spends a large portion of the time unplugged, you might want to hold off upgrading to Mountain Lion for a while. Mountain Lion has a problem of waking up Mac portables when it goes to hibernate mode. That is if you close the lid and leave it disconnected from the power grid for a couple of hours or so, you can’t wake it up and will need to reboot the machine.

This issue is apparent in portable Macs that comes with an SSD drive, like the MacBook Air and the Retina Display MacBook Pro. OS X update 10.8.1 did not fix this issue.

Here is the step-by-step way to test whether you have this problem:

  1. Take a Mac laptop and charge the battery until it’s full.
  2. Close the lid so that it’ll sleep.
  3. Disconnect the power brick from the unit.
  4. Wait at least two hours so that the unit automatically goes into hibernate mode.
  5. With the power brick still disconnected, open the lid and press the space bar or any other key on the keyboard. 

Logically, the unit should wake up. But apparently the screen wakes up (the Apple logo at the back lights up) but shows a black screen. At this point, the only way to access the machine is to hold the power button to reboot it.

If you’re in a hurry, here is a faster way to reproduce the issue:

  1. Charge the laptop until the battery is full.
  2. In the Terminal, type: sudo pmset hibernatemode 25
  3. Close the laptop’s lid.
  4. Wait for about a minute.
  5. Disconnect the power brick from the unit.
  6. With the power brick still disconnected, lift the laptop’s lid.
  7. Try pressing the keyboard or clicking the trackpad – the laptop won’t wake up.

I’ve tried these workarounds but none fixed the problem:

The workaround for now is to disable hibernate mode entirely. Note that your portable will still use the battery while sleeping and thus you might not want it to keep it sleeping overnight without power.

To disable hibernate mode, type this in the Terminal:

sudo pmset -a hibernatemode 0

Whereas to get back to the normal mode, type the following:

sudo pmset -a hibernatemode 3

Type ‘man pmset‘ in the Terminal for further information.

If you work for Apple, please refer to my bug report: rdar://1212084 – please, please get this fixed, pronto ^_^


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