27-inch / 27" iMac Random Shut down

SPECS:____________________________________________________________________________
• 27" 2.8 GHz Intel Core i7 / 8gig / 1TB
• OS 10.6.3 (about to update to 10.6.4)
• All firmware updates have been applied according to software update
• 3 external drives: 1-320 gig 800fw / 1-TB USB 2.0 / 1-500gig USB 2.0

INFORMATION:____________________________________________________________________

I've been running with this configuration ( 3 extra drives) since approximately December with no issues. Out of the blue... only running Aperture and Safari - my iMac JUST SHUTS off- WITHOUTwarning. It acted as though I was running a MacBook and the battery going dead/asleep. That's how random and sudden it shut down - NO WARNING. I did have the iMac asleep for about three hours before coming back to it to start working again when it shut down, but it should have even been cool.

I only started reading around on the web to see of other incidents after this random shut down this evening, but I can't find anything specific. I've found A LOT of similar things - all seemingly related to "HEAT."

And heat seems to be a certain issue recently - in the last day or two. Today I noticed my top back side to be hot, which isn't uncommon, however, it became so hot I really wasn't able to keep my hand on the top back. I've also noticed A LOT of spinning beach balls, and lots of processor delay! Heat??

There are NO energy saver pref's set to automatically shut it down. The power was and is firmly set. There are no network settings, nor access to the iMac to have it shut down. It is not shared with anyone on the network.

SUMMARY:___________________________________________________________________________

• Today, I grabbed a couple temp / monitor widgets and am trying to watch the data. All components seem to be at/around/below 140 degrees F with ambient air at 77 degrees. I don't know numbers, but that all seems reasonable.
• Going to update to OS 10.6.4 (doubt that's it!!)
• I'm going to run the hardware test from my disc to see if ANYTHING. 8-p
• AND... I'm going to call Apple to set up a case. It's still full under warranty, and I have 2 more years of AppleCare on it. But there's been too many things pointing to hardware to call this a software issue.

I've dodged all the display issues with my iMac, but now.. I'm a bit hacked knowing how much I spent on this thing, with the initial DELAYS I went through, ordering it before it had even been released!

?? QUESTION ??_____________________________________________________________________

So, has anyone else been having this issue, heard of a solution, seen anything on Apple's website of known issues ??

Barry
( Grumbling bout my Mac)

Which one of twelve??, Mac OS X (10.5.6), ever hear Newton?!! ;-) One of those, too!

Posted on Jun 22, 2010 8:59 PM

534 replies

Jeff Donald

Level 8

44,754 points

Feb 3, 2011 7:20 AM in response to jorjazz

I would contact OWC about RAM replacement under their warranty. I have the same iMac and it has been flawlessly for almost 2 months with 16GB of the OWC ram. The fact that iMac components have been replaced with no positive affect points towards the ram being the culprit.

jorjazz

Level 1

0 points

Feb 3, 2011 2:25 PM in response to Jeff Donald

Wow! I can't believe I didn't check this before. I apparently have two bad chips from OWC. One bit of weirdness..Owc said they don't need to run in pairs so 12gigs should show up, swapping two of them at seperate times the mac still said 8gigs? However with all 4 chips in, it does register 16g....???

Chalkers

Level 1

0 points

Feb 5, 2011 6:06 PM in response to jorjazz

Weird... The same thing happened with my corsair memory.
Removed 1 of my 4gb memory sticks and rebooted..

checked the memory in "about this mac"only 8gb
where should have showed 12gb..

Shut down removed other 4gb and swapped with the one I removed (put in other slot).. Reboot checked 12gb..

note: all memory in 16gb with many shut downs (approx 2 a day)

Now a wait and see game...

Feb 6, 2011 1:20 AM in response to Chalkers

If you received your iMac with 2 x 2 G apple ram and later bought 4 x 4 G Corsair ram try using : 2x 4 G Corsair ram and 2 x 2 G apple ram.
That should work.
I think that all the slots should contain ram, though not neccesarily equal matched ram.
So 2 x 4 G and 2 x 2 G = 12 G or even 2 x 4 G and 1x4 G plus 1x2 G = 14 G .

As long as you do not have an empty slot in one bank.

peterwillem

Mambirri

Level 1

0 points

Feb 8, 2011 8:40 AM in response to peterwillem

I have been dealing with this behavior for long time too and I have an the following configuration.
Snow Leopard 10.6.6
imac 27" late 09 i7 2.8 Ghz
8 Gb Ram

After trying all possible workarounds I have one that it is working fine so far. The problem seems to be related with the memory is addressed by software in 64 bits. This includes Aperture, Itunes and Safari in y case. When I am using them in 64 bits (default setting) I am seeing this unexpected shutdown/reboot/restart. So far I have been testing them in 32 bits setting and it is working fine (crossing fingers).

If you want to give it a try and provide feedback to others, please do it and if we can confirm that this is a real pattern then lets hope that Apple take a closer look with their nartive applications running in 64 bits.

If you do not know how to switch between 64 to 32 bits try this.
1- Via finder go to Applications folder
2- Select the product you want to change that setting (e.g Aperture, Safari, or iTunes)
3- Right click or "Get Info"
4- Select the check box "Open in 32-bit mode"
5- Re-start the product

If you do not see the check box "Open in 32-bit mode" then your product is native 32 bits.

Well .. good luck and lets see your feedback.

Roberto

Jeff Donald

Level 8

44,754 points

Feb 8, 2011 9:39 AM in response to Mambirri

I only run my iMac in 64 bit and no crashes with 16GB of the OWC ram. There have been several recent posts that OWC changed (tweaked) their ram and it is now working in the 16GB configutation. I can confirm that I've had zero shut downs in 2 months of operation, that includes very heavy Lightroom and Photoshop use.

Are you booting into the 64 bit Kernel?

Feb 8, 2011 10:35 AM in response to Mambirri

@ mambirri

imac 27" late 09 i7 2.8 Ghz

You are talking about the late 2009 model iMac, while the shutdown problems and 16 G ram are happening with the later mid 2010 model iMacs. So you have a different problem with the same sympthoms.

peterwillem

pvillez

Level 1

0 points

Feb 11, 2011 10:41 AM in response to Berry with an A

Its a VERY old issue which afflicts all iMacs going back to the white flat screens. I have an Intel one and the issue is still there no matter what you do to the operating system.

I tried everything. It has been like this for 5 years

No point in calling Apple. The people at the end of the phone have the technical knowhow of burger flippers.

What I have found is a pattern of behaviour in the system:

If after switching on the login screen stays on without blacking. Leave it like this for an hour and then login. It might black out once and then it will stabilise. If it doesn't you could end up doing the restart some 10-12 times.

It is if it were a heating issue, maybe the graphics board needs getting up to a specific heat which might suggest a bad soldering problem.

Forget all the reinstalls, Pram wipes et all. It will not work.

Jeff Donald

Level 8

44,754 points

Feb 11, 2011 11:11 AM in response to pvillez

I'd have to disagree that it affects all iMacs, my mid 2010 hasn't shut down once.

toolman

Level 2

381 points

Feb 11, 2011 1:19 PM in response to Berry with an A

I purchased my 27" imac from Apple in Dec. last year from the refurbished store and have had the random shut down problem almost from day one. The first two weeks it happened two or three times and then went away for two or three weeks. Its now back and it has happened at least 6 times in the last week. Talked to Apple phone help and have gone thru a lot of different things with them but they are at a loss too.

One of the items they wanted was to run the hardware test in the extended mode- did it twice and both times came back OK.

I have two additional sticks of OWC memory installed but even taking them out and going back to just the stock two sticks that came with the computer has not helped.

Wintoons

Level 1

0 points

Feb 12, 2011 12:37 AM in response to Mambirri

Hi Mambirri

You know what? I think you are right. I have Age Of empires 3 on my iMac and everytime I play it, it always switches off. No matter how many times I turn it on and resume playing it again, it switches off every single time. Also, I checked to see if Age of Empires is a 32 or 64 bit program and it doesn't have the option to tick the check box either to be 32 bit.

Good investigation mate 🙂.

Polansky

Level 1

10 points

Feb 12, 2011 2:17 AM in response to Wintoons

No this has nothing to do with it.

However what may be a problem is that one program runs in 32-bit mode while another is in 64-bit mode.

To me the shut downs do not occur if i am running Aperture or Photoshop.
My shutdowns always seems to be related with Safari or Firefox and do always happen after a mouse click

Feb 12, 2011 8:14 AM in response to Wintoons

It makes no difference weather the iMac and OS X is running in 32 or 64 bit mode.
I tried both modes with 16 G OWC ram and had shutdowns all the time.
Only reducing to 12 G ram helped me out.

peterwillem

Wintoons

Level 1

0 points

Feb 12, 2011 11:00 PM in response to Berry with an A

Dumb Question, I have a 24 inch 2009 iMac 3.06Ghz with 8Gig of Ram. Has anyone tried to run 6Gig on one and fixed the problem?

Message was edited by: Wintoons

Feb 13, 2011 6:41 AM in response to Berry with an A

I too am having random shutdown issues my new 27" i7 iMac. I am trying to add 16GB of Crucial memory to the system (confirmed that it is the correct modules). It worked just fine when I lower it back to 12GB (4GB of Apple (Samsung) RAM and 8GB of Crucial).

Tried all the tricks listed here (PRAM reset, SMC reboots, etc.), the only thing that seems to work is the “32-bit plan”. I have tested this theory several times (running the same program in 32 and 64 bit mode) and it appears to work properly without any shutdown in 32-bit mode (Safari, Aperture, Mail and Ripit). Maybe there is a connection between 64 bit programs trying to access 16GB memory? This problem is obviously an isolated issue and not a systemic one across all iMacs. Again, I am researching, testing and talking to both Apple and Crucial about this issue.

I will tell you that the folks at Crucial are outstanding! I really want to use their product, but I need an iMac that can run at full capability (lots of video editing and other high demanding task). I will try to figure the problem out over the next few days, but if it doesn't work out, then I will have to send the memory back and try another solution.

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27-inch / 27" iMac Random Shut down