27" iMac i7 spontaneoulsy shutting down

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

[ Edited ]

I also have a 27" i7 with spontaneous shutdown issues. I have owned the computer for three months with no problems whatsoever. Last week I installed 16GB (4x4GB) of Crucial memory and since then I have had five shutdowns, four of which were while I was sitting at the computer and one was while I was out of the room. At no time was I doing anything that required any serious horsepower from the computer (I was reading web sites or writing email). What troubles me is the computer hasn't shut down during any hard work—processing in Aperture or exporting MPEG movies doesn't cause a shutdown, even when the Activity Monitor shows all four cores churning like crazy. It truly is a random occurrence.

 

I made sure that the RAM was all the same when I received and installed it, so this can't be related to unmatched memory modules. 

 

Years ago I had unending problems with a PowerPC mac, but those went away with the eventual release of an OS update from Apple, so I'm usually willing to sit out any problems through an OS update or two, but I want to make sure to document these troubles when they are new, just in case.

 

EDIT April 18, 2011: I thought I had this problem figured out, but the issues continue....

 

After I posted the first part of this reply, the computer shutdown several times in a short period of time. It kept doing it when I would visit a specific facebook web page. I eventually fixed the cause by updating the two Safari extensions I have installed (AdBlock and Click-to-Flash). After the update, I could visit the aforementioned web page without incident and the computer worked fine for three days. Then the shutdowns began again, averaging once per day with two in the past six hours.

 

I wrote to Apple Support with no response so far.

Binary Boss

Re: 27" iMac i7 spontaneoulsy shutting down

It is most likely a memory issue. I have witnessed this many times on commercial servers. When there is an issue with memory, the system will reboot. Very frequent issue on IBM servers where memory specs are critical. In one case I saw a server that rebooted every 31 to 33 days. IBM replaced every component EXCEPT the third party memory they obviously did not buy from IBM. I encouraged them to call the memory manufacturer and tell them the memory was out of spec and to replace it. They did and the server issue is now gone. No more reboots.

 

I suspect the memory for Apple products is very similar. It has tight specifications and if anything is wrong, the system will shut down.

 

I just experienced this with Crucial memory I purchase for a new 2011 iMac. With both Crucial modules in the system, it will not start. With one (I suspect the good module) it starts and runs fine, but every time the other module is in the system, it will not start...well in one case I got it to start, but in two hours a kernel panic. Removed the module again, and system has been running for days now without an issue.

 

In summary, replace the memory. Something is not right with it.

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

Same, just got yesterday my 16G crucial memory for my Apple iMac 2.93GHz Intel Quad-Core i7 (27-inch - DDR3) Mid 2010.

 

Random instant shutdowns, lowered to 14G (replaced one 4G crucial module with 2G apple), and I still had the same issues. Now, at 12G (4+4 crucial, 2+2 apple) it seems fine.

 

I wonder if the crucial memory I took out is faulty, how to test it?

 

Cheers,

Laurian

Kilobyte Kid

Re: 27" iMac i7 spontaneoulsy shutting down

[ Edited ]

I'm running OS X using the 64-bit kernel and extensions. I installed a 4x4GB ram module in my core i5 27" iMac and experienced the same sort of random power-downs that other users have been experiencing.

 

I immediately thought it was the new ram that was causing the issue. I ran diagnostics for 10 hours, running multiple passes through all addressable memory (the program I was using had a software limitation and couldn't span all 16 gigs, but it covered 15 or so, which should be good enough if there was a major hardware issue.) However, those tests were ran from a command line interface in Single User Mode. They passed all tests just fine.

 

After booting back into the GUI, the issue returned. I got fed up and logged on here to see this thread. It's pretty obvious that this is a clear-cut case of the proverb "you get what you pay for." So apparently, a 4x4GB config of Crucial ram isn't  Mac-friendly. Maybe it'll work in Windows, but then what's the point of having a Mac if you're not going to touch OS X?

 

Whats more, after some research, I found that these chips are all-around much lower quality ***Edited to remove Crucial competitor***. They match the 1333Mhz bus speeds and some of the most prevalent features, but that's those aren't the only metrics to measure RAM's value. For saving an extra 20% of so, this definitely is not worth the headache.

 

I could downgrade to 12GB like some of the other posters here, but mixing 2  + 4 + 4 sticks generally degrades performance because that's considered an asymetrical memory configuration, which increases the latency for hardware address translation and whatnot.

 

Pretty ticked off, requesting an RMA, and never buying from Crucial again. **Edited to remove Crucial competitor**  I understand Crucial gets praise for being a good vendor in general, but this thread shows that there's a significant amount of dissatisfied customers running into a pretty significant and reproducible issue.

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

[ Edited ]

I have had this exact problem ever since installing 16GB of crucial RAM. My temporary fix was to take out 2 of the 4GB Crucial RAM modules and reinstallt he factory 2GB modules. This is DEFINITELY a problem with the Crucial RAM. A more permenant solution, suggested on the Apple Support Forums, is to buy ***Edit to remove Crucial competitor*** RAM. No one who has replaced the Crucial RAM with ***Edit to remove Crucial competitor*** has had this problem. I too am in the process of requesting an RMA, but I would like a refund instead of more bad RAM. 

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

Another 2 full weeks have gone by since pulling half the Crucial RAM and not a single shutdown.  Still waiting for an RMA from Crucial though. Smiley Mad

Kilobyte Kid

Re: 27" iMac i7 spontaneoulsy shutting down

I should update that I had only ever two shutdowns in several months and have 16GB of Crucial RAM in my iMac.  The alst kernel panic was to do with Intego Antivirus  and Lion OSX - so got rid of it and all is well

 

 

Kilobyte Kid

Re: 27" iMac i7 spontaneoulsy shutting down

[ Edited ]

Spoke too soon, have had a few sudden shut downs recently, for no reason - had Lion OSX for a while, but shutdowns are one on Saturday and one tonight!?  Any ideas?  It couldn't be the 16GB crucial after all this time surely?

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

Sigh...I was hoping to find an answer to my random shutdowns. Fail. Seems like the best thing to do is to remove 2 of my 4gb and install the factory ram. signed 16gb ram installer in 2.8 GHz iMac i7

Bit Baby

Re: 27" iMac i7 spontaneoulsy shutting down

Supposedly this is only happening with Crucial RAM. Folks on the Apple Support Forum have reported that other brands do not cause this behavior, even with the full 16GB.