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

JANSJE

Level 1

0 points

Mar 13, 2011 10:27 AM in response to Satoneko

Hi Satoneko,
Thank you for replying. Hope you are safe in Tokyo. What a disasters in your country and it is not yet over! This is very bad and AND WE ARE WORRYING ABOUT OUR iMACS...
Peterwillem: Thank you for your offer, but my dealer sends my RAM free, I suppose, or gets it back from Apple. I hope this will help and otherwise I get a new iMac.

Satoneko

Level 1

15 points

Mar 13, 2011 10:14 PM in response to JANSJE

Thanks for your concern. My family, my self, and the Macs are all fine. In Tokyo, we're not really worried about a nuclear disaster, but more about power shortage as the Fukushima Nuclear Plant supply most of the electricity to Tokyo. Of course, the situation is totally different for the people of northeastern Japan that got hit by the tsunami, but at the moment there is very little I can do, and the fates of those people are in the hands of the rescue workers. For me, I think the best way is to be productive, worry about my iMac so I can stay productive, and that way, we can maintain the economy and indirectly help the people to rebuild.

Mar 14, 2011 9:05 AM in response to Berry with an A

So I'm ready to cut my losses and dump my Crucial memory in favor of something that will stop this problem.

Is the OWC-brand memory absolutely known to cure the shutdown issue, or would I better off ordering the Samsung from here:

http://eshop.macsales.com/shop/memory/iMac/2010/DDR321.527

Tank9

Level 1

0 points

Mar 14, 2011 4:04 PM in response to Berry with an A

Hi, I am reporting in again to say that I have had no problems with 12gb Mushkin ram (3x4gb). Good news I suppose, although I have one 4gb stick sitting around.

Mar 15, 2011 2:15 AM in response to Tank9

Is al that 12 G ram recognized in the iMac? Look in : about this Mac under Hardware.

peterwillem

Jeff Donald

Level 8

44,784 points

Mar 15, 2011 1:05 PM in response to Benjamin Running

I've had 16GB of OWC ram installed since late December with zero issues and I'm a heavy Photoshop, Lightroom and FCP user. You can always talk to OWC first to get answers about their ram, but several users have posted on the Apple boards that OWC has stated that they've tweaked their ram to meet the Apple specs for ram.

rseijas

Level 2

186 points

Mar 16, 2011 1:21 PM in response to Jeff Donald

I'm having this issue now. 27" iMac, Intel 2.93HGz Core i7, 16GB Crucial RAM, 1TB Hard Drive.

I just had two shutdowns within a span of 3 minutes. Only Safari and Mail were open. It's the first time it's shut down while I was using it. I have come back to it after letting it sleep overnight and needed to restart but I figured one of the kids shut it down so I didn't give it any thought. Then I found this discussion.

Crucial has a lifetime guarantee on their RAM, so if using another brand will cure this problem I will give it a shot.

Tank9

Level 1

0 points

Mar 16, 2011 3:43 PM in response to peterwillem

Yes. All 12gb. I am only using the two slots away from the LCD and the one on the right near the LCD. Still no problems. and it's been two weeks. Shut down should have occurred by now.

Mar 16, 2011 4:27 PM in response to Tank9

This is odd. Memory experts, which I am not, claims that memory should be equally divided in the banks/slots. But maybe they say that in order to get a better performance of the computer. Or is this only valid for PC's and not for the Apple machines?
Like to hear some expert opinion on this.

peterwillem

Tank9

Level 1

0 points

Mar 16, 2011 6:05 PM in response to peterwillem

If you downgrade from 16GB(4x4) to 12GB(4x3). Read this.

There are a lot of confused people out there, like Gizmodo which reported that the iMac i7 supports triple channel, confusing DDR3 memory bandwidth with triple channel. But let me make it clear. The iMac owner forums know better. The iMac i7 does not support triple channel simply because the logic board does not support triple channel. You won't see triple channel support anywhere in the Apple store and you won't see a 12GB configuration option like 3x4GB 1333GHz DDR3 SDRAM on there either.

After some more research about the i7 logic board, I concluded that currently all i7 iMacs support DDR3 ram, but not triple channel due to the logic board. The iMac i7 should run optimally in matching speed pairs(1333MHz) to take full advantage of the boards dual channel capabilities.

Mine is running 2x4GB in pairs while the remaining 4GB is running in single mode.

Mar 17, 2011 2:19 AM in response to Tank9

@Tank9

The iMac i7 should run optimally in matching speed pairs(1333MHz) to take full advantage of the >boards dual channel capabilities.

I think you said it yourself, you have to put the ram modules in matching (speed) pairs in order to get optimal performance. And I think 2 x 4 G and 1X 4 G are not pairs. 2 x 2 G and 2 x 4 G are.
Or am I mistaken?

peterwillem

NBChick

Level 1

10 points

Mar 17, 2011 5:06 AM in response to peterwillem

For those that are using Samsung memory and have found it has fixed your shut down problem, what model of RAM is it?

I bought iRam, 2x4GB of it, added it in with the factory 2x2GB. totaling 12GB and the shut downs began. I don't think it's just 16GB configs that cause it. I'm returning the iRam and I want to get Samsung since that seems to be the brand that actually works.

My iMac is the 27" i7 model.

Mar 17, 2011 6:48 AM in response to Berry with an A

I just received my new iMac at the end of February. I immediately installed 16GB of Crucial Memory in the machine. The machine ran perfectly until March 13th, 2011. I updated to Safari 5.04 and Java update 4 on March 12th, 2011. My computer started to randomly shutdown about once every 24 hours, and always while using Safari, no cpu load, and less than 2GB of RAM in use. I experienced this problem on my old iMac and a SMC reset fixed the issue. A simple PRAM/SMC reset did not fix it this time. After looking over the discussion boards, there seemed to be no real answer. Some think it is the RAM, some think it is SMC, some think it is the PSU. Personally, I think it had something to do with the updates last week since the timing and software in use at the time of the crash seemed to be too coincidental.

Personal opinion, after some of these updates I think some computers just need a good wipe. I cannot pinpoint what exactly worked but here is what I did.

1) Ran AHT Extended (2 hours later, no issues)
2) Pulled my RAM and reseated it.
3) Reset PRAM/NVRAM (Whatever it is called today)
4) Reset SMC
5) Booted into Single User Mode
6) Ran Applejack (applejack AUTO restart)

If you don't have Applejack, it is a nice little terminal side utility that you can run in single user mode and it is only 74KB. It repairs the disk, repairs permissions, wipes system cache, wipes virtual memory, and one other operation I cannot remember.

I don't know if this will work for everyone but it fixed my iMac. I think some people are having hardware issues. I think some of us are having software issues.

I hope this helps.

Sincerely,

Jeremy

Tank9

Level 1

0 points

Mar 17, 2011 2:55 PM in response to peterwillem

Correct. My system is not running optimally, but it runs none the less.

Mar 17, 2011 4:41 PM in response to Tank9

@Tank9

My system is not running optimally, but it runs none the less.

So why not use 2 x 4G Mushkin ram and 2 x 2 G Apple original ram (that came with the computer)?
Or did you have the 16 G Mushkin ram from the start and no original Apple ram?

peterwillem

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27-inch / 27" iMac Random Shut down