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Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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iMac freezes up randomly, 1st core 99% kernel process

2012 iMac 27" Mavericks

Since getting my iMac (refurbished from Apple... I know, I know... but the price was soooo good) I have had a problem with it freezing up randomly. Sometimes it will happen 2-3 times in one day, sometimes not for a week or so. First my browser gets laggy (Chrome or Safari, doesn't matter) and my fan starts racing and then I get the spinning beach ball as my first cpu core spikes to 99% and activity shows a kernel process taking over (is this what's called a Kernel panic?). I am still able to close a few programs in the first 30 seconds or so but then all I can do is move the cursor. I used a shareware temp gauge to check temp (since time-expired) that did not indicate overheating. I asked apple for help but all they could offer was shutting off the computer, unplugging it for 30 seconds, plugging back in and then waiting another 5 seconds to reset the power management chip. I have tried this numerous times with no help. Is this probably hardware or could this be a software issue? I uninstalled Java for a while but that made no difference either. I have about 3 months left before my year is up if I need to bring it in to Apple though the Apple folks have never been able to solve a problem for me before short of charging me to replace a bunch of stuff for many $100s.

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Sadly, it sounds like your HD is in trouble! This could be just a be a messed up system file, badly fragmented disk or the disk could be failing.

Before starting make sure you have made a full backup of your apps and data!

Lets do this:

First you'll need to create (if you don't already have one) a bootable external drive. This could be a simple USB thumb drive (USB3 is best) or you could have a Thunderbolt HD or SSD unit. Once you have prepped the drive you will need to boot up under it.

Think of it this way you can't resole your shoe while you are still wearing it! That is why we need to boot up with the external drive.

OK, now you'll need to run Disk Utility from the external drives application folder. Run the repair permissions first (run it a few times to make sure all of the errors are fixed) then run repair the disk making sure you have selected the correct drive did it run though without any serious errors? Again you may want to run it though a second time. If it can't fix the error you need a new HD

Restart the system this time off of the internal drive is it better? If not you'll need to get a defragmentation application for the next step. I would recommend Drive Genius This is for the HD not the SSD drive! Sadly, you will need to buy the full package as the test version won't defrag the drive. Yes, there are a few freebie's out their that will do the job I've had too many bad experiences with them so I stick with a well supported app like this one. See how badly fragmented the drive is and let us know how it goes.

If the drive still is having problems we may need to look at other directions here. I would say better than 80% of the time this fixes things, 15% the drive has gone and the last 5% is the strange stuff.

Good Luck!

Lastly, Temperature Gauge is also a very good fan & temp app I recommend if you need a good one.

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Thanks, Dan. I did run the disk utility a few times from the drive itself (or, if I understand it, directly from Apple's servers as there is now some kind of online version that I boot into) and ran all the permission fixes. I'll scare up a USB3 drive during the week somewhere and try that. How do I create the bootable drive? Is there already an option in the disc utility to do so? I've also run the hardware check a number of times with no errors shown.


What you ran was the recovery partition OS which still is on the HD - You still have your toes in the shoe ;-} While the recovery tools can be use full here you can't really fix the low level part of the disk while any partition is active.


The fact it didn't find any errors is a good sign here. Still test it again with the USB drive. Download (if you don't have a copy of it already) the Mavericks OS installer from the App Store (or what you are running as the OS on this system). It will walk you though the process.


Sorry I didn't follow up on this earlier but I had to get a USB3 drive to boot into. I did so and ran the disk utilities several times. The drive looked good with just a few permissions to fix. While the iMac was booted up from the usb drive it froze up twice, spinning beachball and all, both times requiring a restart.

I'm not so sure it is the hard drive. What are some other possibilities?


Still could be the HD. As the drive heats up it may fail then Vs when its cool. Did you run the drive repair option besides the repair permissions? The beach ball is a hung process. If the internal drive was being accessed. If you had nothing going on on the internal drive (only using the external drives apps) then thats starting to sound like a logic board issue popping up.


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was this problem resolved? I have exactly the same issue. All HW tests pass and I also got the logic board replaced. fresh reinstalled OS (after wiping full HDD) No cigar.

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Did you swap out the HD at some point?


Arjun, I still have the problem. I have not had a chance to bring the iMac in for service since the nearest Apple store is an hour away. Sometimes the lockup happens right after startup and keeps happening over and over and sometimes it doesn't happen for a week. Very frustrating.


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Thank you for your response.

I've been following this up aggressively and Apple has escalated me to their next level of support folks - I had a call this morning. I'll keep you posted with details as they progress.

I video recorded what was going on when Apple kept telling me it was a 3rd party installed software problem - .

No, I haven't gotten around replacing either the HDD or memory yet - I hope apple just swaps my iMac - its an expensive paperweight for me right now.

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Okay, here is an update:

a) Apple's support is very disappointing. It was escalated to a higher level and I worked directly with a person (contractor, but address) who helped me over one call, assigned a case id and then completely disappeared after that, despite my followups. Maybe he gave up, but this was rather unprofessional considering Apple's reputation.

b) Anyway, left to myself, I had a hunch that Safari was the problem child, because really most of what we do is browse. Naturally, my first instinct led me to keep clearing the caches - both Flash and otherwise. Instead of relying on my doing it manually, I created a LaunchDaemon that would run twice a day and remove everything. My system has since been *much* more stable. I have only rare beach balling issues, but again that may change. I've been observing this good behavior for the past 3-4 weeks.

Here is my script that runs twice a day: (make sure you do a chmod a+x bin/

[Arjun@~]$ cat bin/

rm -rf "/Users/Arjun/Library/Preferences/Macromedia/Flash Player/#SharedObjects/"

rm -fr "/Users/Arjun/Library/Caches/*"

rm -fr "/Users/Arjun/Library/Caches/*"

echo Flash and Safari cache last cleaned on `date` > /Users/Arjun/bin/cacheclean.log

Here is the LaunchDaemon plist:

[Arjun@~]$ cat /Library/LaunchDaemons/com.arjun.cacheclean.plist

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" ">

<plist version="1.0">












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staggerwing will be eternally grateful.
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