27-inch / 27" iMac Random Shut down

Ever since I upgraded from Lion 7.0 to 7.0.1 I've been having shutdown problems again (been running great the past eyar since I installed the Samsung RAM that Apple sent me).

If I remove two sticks (bringing it down to 8GB) it runs fine (just very slow because I run a lot of server development apps). I'm super-swamped with work, but will be likely brining it in for repair soon. In another thread a guy seems to ahve the same problem. They replaced his logic board, but he's still having issues.

...sigh =\

That's bad news 😟

I finally replaced my Crucial ram with Samsung ram from OWC/macsales.com and have been doing great ever since - no shutdowns at all with full iPhoto usage (that I used to not be able to do)

Has anyone else on this thread upgraded to 7.0 or 7.01 and re-experienced issues after previously solving them with new RAM?

This is a really interesting thread. I have a late model 2011 iMac with an i7 and 16GB of Crucial RAM. I have never had an issue with random shutdowns or black screens, thankfully, but I do have an issue where I can't install anything by disk -- https://discussions.apple.com/thread/3471027

I wonder if this is the same issue. I'm on 10.6.8 but am thinking of upgrading to Lion. Does anyone have new information on how their iMac is running on Lion, especially with 16GB of Crucial RAM?

Crucial offered me an RMA, but I don't know if that's going to really solve the issue. All my tests (inlcuding 24hours of Memtest) came up totally spotless...

Still having problems after upgrading to Lion. Tried with 16GB Crucial memory, had to reduce down to 12 because of the random shutdowns. Same on Snow Leopard with Kingston 16GB and Crucial 16GB. No way to reproduce the problem, it just happens.

Teemula, do you experience any issues after dropping down to 12? Or is everything fine at that point?

Not a single problem with this issue after dropping one of the sticks out and using iMac with 12GB. Its been running just fine.

Just to add, it's been 2.5 months since I pulled one of the 4GB sticks out of mine (reducing it to 12GB) and it's been running perfectly since then.. I did contact Corsair, but got some wishwashy response and really couldn't be bothered with the hassle, so I've used the spare stick to bolster up a laptop that only had 4GB before 🙂

For those that are still having issue, either contact the manufactur of the ram and request/demand a replacement or a refund of what you paid. So far from the sounds of it, Samsung and Mushkin have solved there issues. I have been running 16 GB, running Dreamweaver, photoshop, xcode, aperture + 10 other programs at the same time, with at least 16 days of uptime without a shutdown. So, since you paid for an imac that supports 16 gb, and paid for 16 gb, don't settle for 12.

I too have been running with 12GB only after the full 16GB (Crucial RAM) caused the random shutdown issue for me. I pulled two of the 4GB modules and put two of the original 2GB modules back in. I'm running 2x4GB and 2x2GB, and I haven't had a single shutdown ever since doing so. I don't notice any performance difference between my current 12GB configuration vs. 16GB.

Just to shoot you guys and update in terms of what worked for me:

Yes the problem is due to using 16GB of RAM. This problem does not seem to occur when using 12 GB of RAM.

I've conducted these tests using Premire. With 16GB crash after the computer reaches a certain temperature (apx. 120-130C), the computer will shut down. With 12 GB the temperatures seem to not trigger the issue below.

These 27" imacs suffer from this issue:

It turns out that Mac Intel chips have a built-in feature called THERMTRIP that will temporarily suspend the CPU when things get hot, and shut down the CPU altogether when things get too hot. Speculation is that this temperature is somewhere in the neighborhood of 120-130ºC.

One way to workaround this issue is to use the smcFanControl app. I use it and have configured a setting that boosts the ODD and CPU fan speeds to keep the temperature below 120-130C. This seems to be working well.

You can use iStat Pro to monitor your temp. However, the smcFanControl app also monitors your temp.

I strongly feel that Apple should do something regarding this issue. If you use Applecare, they'll just say that they can't find anything wrong, or will replace the MB only to have the problem reoccur. They may also suggest purchasing new RAM, which many have done with no luck.

Hope this helps. Please reply if you are able to get a realistic resolution from Apple.

shadowhywind wrote:

For those that are still having issue, either contact the manufactur of the ram and request/demand a replacement or a refund of what you paid. So far from the sounds of it, Samsung and Mushkin have solved there issues. I have been running 16 GB, running Dreamweaver, photoshop, xcode, aperture + 10 other programs at the same time, with at least 16 days of uptime without a shutdown. So, since you paid for an imac that supports 16 gb, and paid for 16 gb, don't settle for 12.

Are you running these on Lion? How has it performed since your last post? what are your temps when using these apps?

teemula wrote:

Still having problems after upgrading to Lion. Tried with 16GB Crucial memory, had to reduce down to 12 because of the random shutdowns. Same on Snow Leopard with Kingston 16GB and Crucial 16GB. No way to reproduce the problem, it just happens.

See my quote below regarding temperatures. Lion also, seems to increase CPU temps across the board.

It turns out that Mac Intel chips have a built-in feature called THERMTRIP that will temporarily suspend the CPU when things get hot, and shut down the CPU altogether when things get too hot. Speculation is that this temperature is somewhere in the neighborhood of 120-130ºC.

Problem SOLVED!

I got new memory from Kingston and it fixed everything. No problems after two weeks of regular (and sometimes heavy) use. Photoshop, Final Cut Pro, Illustrator, InDesign running almost full time with some standard apps and no problems at all, not a single shutdown.

I haven`t done anything else to my iMac, just replaced 12GB of Crucial to 16GB of new Kingston Ram. No major updates on Lion, no extra installs, nothing.

Whole thing started in november 2010 when I bought my iMac with 16GB Kingston memory. System started crashing in first week, I took 4GB out and it was fine. Received 16GB of new Kingston memory, problem persisted. Changed to 16GB Crucial memory, problem persisted. I was in the middle of a big project and had to get stable system so I took 4GB off and everything was fine. Two weeks ago I received 4x4GB of new Kingston RAM and this fixed my problems. Now running 16GB and everything is rock solid as it was supposed to be in the first place.

teemula,

The odd thing for me, my computer ran fine for the first 6 months and now I have random Kernal shut downs, they ran a system hardware check and my SSD Drive was corrupt. They replaced the drive everything seemed fine for a week or so and then it started happening all over again. First Mac in 8 years with any problems, but this problem is driving me nuts! I have 3 years of Apple care, I wouldn't have an issue with taking it in again but, hauling a iMac into the store is a pain in the ***!

My system is a iMac 27" i7 with 16gig of Apple memory with SSD drive and 2TB hard drive.

Using 10.6.8

I have done all the reseting of everything several times over a replacement drive etc.. Open to any suggestions

as last night while runing Preview looking at several pictures, it crashed about 5 times.

Thanks for any help!

Gandalf The Grey wrote:

teemula,

The odd thing for me, my computer ran fine for the first 6 months and now I have random Kernal shut downs, they ran a system hardware check and my SSD Drive was corrupt. They replaced the drive everything seemed fine for a week or so and then it started happening all over again. First Mac in 8 years with any problems, but this problem is driving me nuts! I have 3 years of Apple care, I wouldn't have an issue with taking it in again but, hauling a iMac into the store is a pain in the ***!

My system is a iMac 27" i7 with 16gig of Apple memory with SSD drive and 2TB hard drive.

Using 10.6.8

I have done all the reseting of everything several times over a replacement drive etc.. Open to any suggestions

as last night while runing Preview looking at several pictures, it crashed about 5 times.

Thanks for any help!

I would probably try to do a fresh install of the OS, or upgrade to Lion since you are experiencing kernal errors. Have you zapped the PRAM? Try downgrading to 12GB of RAM to see if that resolves the problem also.