iMac crashes, hardware tests ok

Hey guys,

I've finally come across an OSX problem I can't untangle. My iMac started to crash occasionally to the grey screen, so I did the usual (repair permissions, repair disk, safe mode) and it would be ok for awhile. It started crashing again, this time restarting immediately, so I did a hardware test and everything checked out. I took it to a Genius Bar and their diagnostics also showed that my hardware was working normally. I was told it could be a software problem so I reinstalled OSX and restored from a Time Machine Backup. Then my iMac started crashing and restarting several times a day until finally it wouldn't boot up at all. I took it back to the Genius Bar, where again, they found that the hardware was fine.

Does anyone have a suggestion as to where I can start to look for the issue? If I posted my crash logs, would anyone here be able to spot something amiss? I was also having trouble with a faulty Time Capsule recently. (In fact, I can't even access my old backups to restore from; thank goodness I made a second backup on a FireWire drive.) Also, when I repair permissions, I see a LOT of "ACL found but not expected" messages. Could this indicate something more specific? I don't expect anyone to pinpoint the exact cause, but I'd like to at least narrow things down before I hassle with installing all of my many apps all over agains and trying to recover all my preferences.

I have a 2011 21" iMac with a 2.8 quad core processor and 16GB of RAM. Thanks in advance!

In short: iMac is crashing and restarting 3x a day and all hardware passes diagnostics.

I had the same exact machine as you have but my crashes turned out to be a defective hard drive which Apple replaced under my Apple Care warranty. However, their diagnostics at the Apple Store pinpointed the hard drive as the culprit immediately. Your crashes could still be hardware related especially if it's intermittent. Power supply problems and memory problems can cause intermittent crashes. However, at this point in time you may be better off doing a clean test install (minimal apps) to see what happens. If the crashes occur under that scenario, I would say it's likely a hardware intermittent failure of some sort.

Thanks dude. I'm reinstalling one more time, though I'm almost hoping it is hardware related since in that case I'd at least know I can fix the problem. We'll see how it goes!

If your external drive is a bootable clone, try booting off that and using it that way for a while. That will provide a clue to whether the problem is the internal drive or not.

BTW, have you done any hardware upgrades yourself? Especially with the RAM?

Unfortunately I don't have a bootable clone. I've never needed one in all my years as a Mac user.

The only thing I've upgraded myself is the RAM, which also seems to check out ok.

Oneironaut said:

Unfortunately I don't have a bootable clone. I've never needed one in all my years as a Mac user.

The only thing I've upgraded myself is the RAM, which also seems to check out ok.

Click to expand...

When did you do the upgrade, and when did the problems start? Did you replace the existing RAM and add all new identical sticks, or just add more?

Is it still crashing and restarting while booted in Safe Boot Mode, and also disconnect any peripherals except any needed mouse and keyboard while trying.

I just finished a similar problem with a Mac Mini that crashed very intermittently over the course of almost 6 months. The only way I was able to find the problem was to run memtest over a 24 hour period. On pass 8 it finally failed with a memory issue. I replaced the RAM under warranty and all is running nice and smooth now.

I downloaded Memtest rather than running the Apple hardware test as the Apple software never found the RAM issue and neither did the Genius Bar as the system is under AppleCare.

Bill

Hey guys....

I think I just added more RAM as soon as I bought the iMac three years ago, and the problem only started a few weeks ago. But I may have bought all new sticks. I'll check as soon as my restore is done.

I don't think I had it running long enough in Safe Mode to discern if it was still crashing. It would only crash after awhile, at seemingly random times. However, I didn't even bother to boot it up in safe mode when it stopped booting up completely. I just got fed up and brought it back to the Genius Bar. I do remember that once after attempting to repair the disk from the repair volume, the OSX hard drive stopped showing up as a bootable disk.

Finally, I don't have many things connected to my iMac. All I really have is two portable drives, but I had them with me when I was away for a week and the crashes still happened during that time. Other than that, I just have a Time Capsule and a printer connected wirelessly.

Bbogess, thanks for the tip. I'm definitely going to check out memtest!

Oneironaut said:

Bbogess, thanks for the tip. I'm definitely going to check out memtest!

Click to expand...

Are you getting kernel panics? If so..many times kernel panics are hardware related. AND...if the ram was replaced/upgraded recently...ram (I have found to be) the #1 reason for hardware-related kernel panics. Sometimes new ram can be bad...or non-new ram inserted can be bad...or using the wrong ram.

Ram can occasionally fail as well...so even if the ram wasn't upgraded recently...I wouldn't discount ram being the issue.

Depending on the ram configuration...testing for bad ram is easy. Just remove all sticks of ram...insert one...then test. Keep going until all ram sticks are tested (single sticks...tested one by one). Or in pairs if the model Mac in question requires pairs of ram.

- Nick

To test your RAM, try using Rember. It's a graphical frontend for memtest.
Test for Defective RAM Modules Easily with Rember for Mac OS X | OSXDaily

Thanks guys!

Pigoo, I would get kernel panics at first, but after awhile, it would just crash then restart automatically. The RAM is not new and has been in there since the day I bought it but it sounds like something I should test out. Thank you guys for helping me narrow this down a bit.

Any chance it could be a corrupted system file, maybe something in my Library?

Oneironaut said:

Thanks guys!

Pigoo, I would get kernel panics at first, but after awhile, it would just crash then restart automatically. The RAM is not new and has been in there since the day I bought it but it sounds like something I should test out. Thank you guys for helping me narrow this down a bit.

Any chance it could be a corrupted system file, maybe something in my Library?

Click to expand...

You could have a faulty kernel extension. Running the following command in Terminal will list all non-Apple kexts that are loaded:

Ok, here are the results of the kext command:

kextstat | grep -v com.apple
Index Refs Address Size Wired Name (Version) <Linked Against>
80 0 0xffffff7f8177a000 0x3000 0x3000 com.paceap.kext.pacesupport.snowleopard (5.9.1) <7 5 4 3 1>
139 0 0xffffff7f825ef000 0x5000 0x5000 com.logmein.driver.LogMeInSoundDriver (1.0.3) <118 5 4 3>
141 0 0xffffff7f825f9000 0x5000 0x5000 com.Cycling74.driver.Soundflower (1.5.1) <118 5 4 3>
Anthony-Medels-iMac:~ anthonymedel$





Rembar detected errors and displayed this log:

Running 1 test sequence... (CTRL-C to quit)

Test sequence 1 of 1:

Running tests on full 7703MB region...
Stuck Address : setting 1 of 16

FAILURE! Data mismatch at local address 0x0000000113b50028
Actual Data: 0xffffffffec4affd7

Linear PRN : setting 1 of 16

If I had to take a guess, I'd say it's a RAM problem or something to do with the Snow Leopard kext. What do you think?

Edit: After looking into it, I see that PACE is some kind of anti-piracy protection that is installed along with some kinds of software. It could also be an iLok dongle, which is something I see in some logs a lot but have no memory of having.

Yup. Bad RAM. Check OWC for some new sticks. Just pick your model and you can find the right RAM for yours. I do recommend testing them after install just to verify they are all good.
MyOWC at OtherWorldComputing.com

EDIT: consider making a backup copy of that paceap kext, then delete the original. I don't like the idea of an anti-piracy measure installing a kernel extension. Also, just for kicks, reboot into Safe Mode, then re-run Rember. That will load only the minimum kernel extensions necessary to boot up. I don't imagine that a bad kext would cause a memory failure, but may as well try for laughs.

Thanks so much for your input, all of you! I'll look into some new RAM.

Any suggestions on how to find the paceap kext? I'm not seeing it in any Finder searches.

Oneironaut said:

Thanks so much for your input, all of you! I'll look into some new RAM.

Any suggestions on how to find the paceap kext? I'm not seeing it in any Finder searches.

Click to expand...

Forget using Spotlight (aka: Stoplight) for finding files and get "Find Any File" downloaded onto to your Mac and use it. It will find any filename you search for.

http://apps.tempel.org/FindAnyFile/

Download Find Any File for Mac - Search your disks for files using various criteria. MacUpdate.com

Oneironaut said:

Thanks so much for your input, all of you! I'll look into some new RAM.

Any suggestions on how to find the paceap kext? I'm not seeing it in any Finder searches.

Click to expand...

3rd party kernel extensions should be in /Library/Extensions, but some apps put them in /System/Library/Extensions. Be very careful in doing anything in /System.

As an aside, I found an interesting discussion on Apple's forums. Someone had the same problem you had using over-specced RAM. Just a reminder to be sure you get modules certified for your model.
https://discussions.apple.com/thread/4906714

Thanks for that. Interesting, it isn't finding it, just the Safari search I did on the kext. When I used AppCleaner to test uninstalling the iLok License Manager, it didn't show up there either. Any thoughts? Maybe I'll just see if the new RAM solves the issue before bothering with this Pace thing.

EDIT: I did find PACESupportFamily.kext. Could this be it?