Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Shutting down when 'cold'

My computer:

  • iMac (27-inch Core i7, Mid 2011)
  • Radeon HD 6970M (2 GB)
  • OS X 10.10.1

I have a weird problem with my iMac. The machine crashes when it is cold.

So if the iMac has been sleeping it will crash almost always when waking up. Or when I boot the machine when it has been unused (cold), it will crash if I start a program ’too fast’. This period seems to vary, but three minutes is too little it to ’warm up’. And around 8 to 10 minutes it won’t crash when I start programs. Sometimes iMac crashes when booting to Os X too (if too ’cold’).

To avoid this I can push option-key (choose operating system menu) and let iMac to ’warm up’ some time. When using the iMac ’warm’ I can do anything and it doesn’t crash - gaming, photo editing, encode movies etc. I can also boot the machine without any problems if it is warm.

But here is a twist with this problem: Using bootcamp and Windows 7 the iMac doesnt crash EVER - cold or warm. Weird.

My guess is that there is something wrong with power unit, motherboard or display adapter. Maybe some component had too much thermal expansion somewhere? I would take this machine to service, but I am pretty sure they only charge me 70 euros for opening the machine and can’t do much. Replacing all three components seems too pricy too. Anyone else ever experienced this kind of problem?

Here is a list of things I have tried this far:

  • Reinstalling Os X (cleang install). I have tried both 10.9 and 10.10.
  • Hardware test (long or short) doesn’t find any problems.
  • SMC reset.
  • PRAM reset.
  • I have tried using different memory chips. And also on different slots (the iMac has four).
  • Have disabled wifi and bluetooth.
  • Used different power cord and took computer to another room for another power socket.
  • Used external firewire hard disk for Os X (10.6). Crashed also when ’cold’.
  • Have connected three external usb harddrives when booting (’trying to overload faulty power unit’). No problem at boot.
Answered! View the answer I have this problem too

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My iMac is exactly the same as yours and I have the same weird problem with it! A Apple Service Partner made a system check and didn't find out anything wrong with my iMac.

Do the crashes occur when you burn a CD/DVD with the internal ODD using OS X? - My iMac crashed everytime I burned something onto a DVD.


Burned a DVD using OS X. No problems there. (As long as iMac had been properly warmed up (10 minutes).)


Ok, thanks for trying this out! I really have no more ideas where this problem comes from. The temperature needed seems like a hardware problem but the fact that everything works with Windows seems like a software problem.


Have you tried a good temp monitoring app which can log things. Temperature Gauge Pro might be a good choice here that way you can see whats happens just up to the point the system crashed, if you think its temperature related.


While you both have crashing systems the root cause it likely different here given the fact the burner fails for one of you and not the other.


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Chosen Solution

There's your problem OS 10.9 and 10.10 have had a plethora of wake from sleep issues. Go back to 10.8.5 (bet everything was working fine then?). Or, keep using your workaround.

This seems to be an OS not a hardware problem - hence your USB idea generated no information.

That Windows works fine again points to the OS.

Unless you have some new peripheral that demands 10.9 or 10.10 wait until a couple of "fixes" for those OS's have been generated, and then do the install followed by all the updates before use.

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I completely concur. It's the Mac OS.


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We have quite a few 27" iMac Mid '11 systems that the team leave on overnight in sleep mode without any crashes running 10.9 (we haven't rolled out 10.10 yet).

While I've seen issues in MacBook Pros with sleep issues related to OS-X, I haven't seen them in iMac's. I suspect the lid sleep option vs the timeout/menu option maybe a factor in the MacBook Pro's.

I think your data point between running OS-X only Vs OS-X with BootCamp running is a clue here. I would look at the Activity Monitor to see what is running between the two configs. See what is different either processes running and/or the version of the process. Lastly, I would also look to see if anything maybe running in background in the OS-X w/BootCamp setup. Maybe something is keeping your system warm.

I'm leaning more into a hardware issue given our systems not messing up. Mind you we run business apps no gaming or other odd stuff. My home system runs some games and video editing while I don't often leave my system running what I have its not crashing like yours.

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