iMac Freezes (npvhash=4095)

[S.B.G]

Well, my brand new (refurb) iMac 27”, i7, 16GB RAM, 1TB HDD (see Blown Away) is experiencing some frustrating problem that I cannot figure out. For what appears to be no reason at all, it will freeze up totally. No keyboard, mouse or Magic Trackpad actions will accomplish anything. The only button that works is the power button. When the iMac indiscriminately freezes, I hold the power button until it turns off. Then I can turn it back on again. This all started about 2 weeks ago.

I can be browsing in Safari, reading Mail, adjusting System Preferences or doing nothing at all and it will freeze. It will freeze minutes after waking from sleep or hours or days. It will freeze after a warm boot and after a cold boot in minutes, hours or days; it freezes at a time of it’s choosing. It will freeze if there are open applications in the Dock or no open applications in the Dock.

The only thing I can see as a pattern (almost) is that I haven’t noticed that it freezes while music is playing in iTunes. The other day I was listening to music for a few hours and it never froze up. Then I paused the music, went outside to load the wood burner and came back in about 4 minutes later to find the iMac frozen again.

Every time it freezes and I boot it up again I check the Console. At first I saw several applications with problems and I fixed them by uninstalling them or searching the problem on Google and finding the solution. But still the freezing continues. Those issues were actually dated a few weeks prior to the beginning of the problem. One problem I had was that my WD MyBook HDD which I use for Time Machine was going bad and had crashed my iMac once. I had to wipe the drive and use Disk Utility to repair it. That worked for a week or so and then the drive crashed permanently to where I couldn’t repair it at all or even SpinRite it with an IBM PC. When it crashed for the last time I was in the middle of all the freezes and trying numerous things to fix it. So I was worried a little that I was without a backup and having troubles. I had ordered another drive from OWC and that came in and I got it running and backed up again successfully with Time Machine.

In the Console, every time it freezes, I look at the time stamp to see what was going on. But I never find anything faulting except a Kernel panic which reads “npvhash=4095.” A Google search only turned up something about corrupt fonts in the Font Book. So I went there and found a few duplicate fonts and repaired them, but that didn’t solve the freezing problem. Every application that was logged around freeze time, I checked out and stopped the next time to isolate the issue but haven’t been successful.

The first time I found it frozen was a day that I was downloading a video podcast in iTunes which was about 400MB or so. I left it downloading and set the display to sleep after 1 minute and the computer to sleep after 3 hours which I figured would be enough time to download as my connection speed is a bit slow. Then I left for work. When I returned home, the computer was still on and not asleep and completely frozen.

Another thing I keep seeing in Console are messages that read “Firewall[64] Stealth Mode connection attempt to TCP (or UDP) 192.168.0.194: (various port numbers) from 192.168.0.1: (various port numbers). Now .0.194 is the iMac and .0.1 is the router. Sometimes the sending IP is a public IP.

(My AEBS is bridged to a Cradlepoint MBR-259 router which is then connected to a Sprint MiFi device for Internet service.)

Below is a list of things I have gone through to try and solve the problem but so far none have worked.

• Disk Utility: Verify Disk Permissions, Repair Disk Permissions, multiple times
• Disk Utility: Verify Disk and it showed to be just fine
• Have SMARTReporter for HDD and it always reports that it is fine (though I never trust SMART as it doesn’t really work that well)
• Disabled GeekTool, then uninstalled GeekTool
• Repaired Font Book fonts
• Uninstalled Sierra Wireless Watcher (from the days when I had an AT&T air card)
• Reset PRAM & SMC
• Removed WD Drive Manager as it was one thing listed in Console that had an issue
• Used the app TrashMe to remove all third party apps and preferences that I was no longer using
• Turned off the OS/X Stealth Mode
• Turned off the OS/X Firewall
• All software and firmware updates have been checked and applied for OS/X, AEBS, Cradlepoint MBR-259 router and Sprint MiFi.
• Restarted all routers
• Apple hardware diagnostic utility (reboot computer while holding letter G or H, I forget which one now) and running the test showed all hardware to be working fine
• Ran Remember RAM tester and all 16GB OWC RAM checked out fine
• Uninstalled Adobe Flash
• Uninstalled Adobe Updater
• Turned off Bluetooth
• Used Onyx to:check SMART status, Structure of volume, Preferences, Permissions, Delete the caches of Boot, Kernel, International Preferences, QuickTime components, Other components, and nearly all of the things listed under Cleaning
• Created a new user account and within 2 minutes of using that one iMac froze up
• Backed up entire drive with Time Machine, inserted OS/X disc and rebooted, erased entire iMac HDD and reinstalled OS/X and then migrated apps, account info etc... from Time Machine and applied all Software Updates to OS/X bringing it back to 10.6.6 and computer still freezes
• Computer is plugged into an APC UPS unit

About the only thing that I can find that is consistent, as I had already mentioned, was the console message npvhash=4095 and that so far it seems to not freeze while playing music in iTunes.

Now before I go and drive an hour in one direction to get to my nearest Apple Store and drop this off to them to figure out, I call upon the vast and knowledgeable members and resources of MacRumors to assist me in anything that I may have not done to figure this out.

 

[wrldwzrd89]

This sounds like a bad PMU setting. A quick trip to the Apple Store is the simplest way to get this fixed. I know this, I had the exact same problem with a PowerPC iMac G5 I had. As soon as the PMU reset was performed, the random crashing and freezing stopped.

 

[S.B.G]

This sounds like a bad PMU setting. A quick trip to the Apple Store is the simplest way to get this fixed. I know this, I had the exact same problem with a PowerPC iMac G5 I had. As soon as the PMU reset was performed, the random crashing and freezing stopped.

What is the PMU and does the Apple Store have to do it, or am I able to do it?

I added an edit to my OP, I had also reset the PRAM and SMC which also had no affect.

EDIT: After a Google search led me to the Apple support site, it appears that the PMU is for iBooks and PowerBooks. I have an Intel iMac so that isn't going to help. I appreciate the try though.

 

[wrldwzrd89]

What is the PMU and does the Apple Store have to do it, or am I able to do it?

I added an edit to my OP, I had also reset the PRAM and SMC which also had no affect.

EDIT: After a Google search led me to the Apple support site, it appears that the PMU is for iBooks and PowerBooks. I have an Intel iMac so that isn't going to help. I appreciate the try though.

PowerPC iMacs have one too... and I believe Intel iMacs also have one, though I have no idea where it is located... ah, I Googled and found that the PMU equivalent in an Intel Mac is the SMC (System Management Controller). Looks like you reset that already.

 

[S.B.G]

Update Time

Ok, it's time for an update to my iMac issues. I've been decidedly absent from MR for a couple of weeks partly because of the iMac issues and because my job is taking a lot of my time right now.

After all the troubleshooting I have done myself I took it in to the Apple Store at Partridge Creek and they kept it for 9 days testing it with everything they could and were only able to replicate my problem once. They said they had every application open that they could and ran their RAM and CPU tests on it the whole time. All their stress tests could not pinpoint the problem.

I then took it home and plugged it back in and within 20 minutes it started all over again freezing. I then decided to look in the direction of my peripherals as the cause for the crashes. One by one I unplugged and uninstalled all the corresponding software to the connected devices.

• APC UPS Powerchute Personal Edition battery backup monitor
• USB Time Machine drive
• RJ45 Ethernet adapter and switched to the Airport card
• Logitech Performance MX mouse and software and switched to the Magic Trackpad
• Apple wired keyboard and switched to the Apple wireless keyboard

So then the only thing connected physically was the power cord and it continued to freeze. Then I took out the 16GB OWC RAM and replaced it with the original 4GB Samsung RAM that Apple shipped it with. All that did was stop the random freezing and caused it to only freeze when waking from sleep, just prior to logging in. Once I rebooted it started giving me Crash Reports for the first time. I checked them all out and they were something different every time.

I even shutdown the Airport card and left the RJ45 Ethernet connection unplugged so it couldn't have any network or Internet traffic coming to it, just in case there was something flooding the ports with crap data causing the crashes.

Then I decided to wipe the HDD again and reinstall OS/X. I did that by erasing the HDD and then installing the OS as a fresh install. Once done, I made a generic account and the only thing I changed was the sleep and wake settings. I always have the iMac wake up at 6am everyday. I didn't apply any Software updates or migrate my data from Time Machine. I left it at 10.6.4 from the disc and that was it. Still it continues to crash after waking from sleep. (This is still with no network or Internet connection) I did get one kernel panic message when I was adding the wireless keyboard in Bluetooth before I wiped the HDD and the crash report was totally unrelated.

So, I took it back to the Apple Store 4 days after they gave it back to me. As an IT administrator, I felt I have done everything I can possibly do before taking it to Apple. (I did some other things too, but didn't detail them here). I kept a log of everything I did from the start and turned it over to the Apple employees at the store so they could see what I tried to remedy the problems.

I went in there today, expecting to have them check it over again with the original RAM installed and without any of my data on it, in case there was something in my profile causing problems. But the store employee decided he would override company policy and give me a brand new replacement iMac even though the one I had was a refurb. They have a policy of not replacing refurbs with brand new machines, but they waived it in my case.

I didn't mention or even ask for a replacement of any kind and they offered it to me. I accepted of course. They said they would have to order one as they don't normally stock iMac's with the specs I had. So they will call me when the new one comes in.

They told me that they would be shipping this defective iMac back to Cupertino to have their engineering team go over it and determine what the problem is and that my notes would go with it for them to view. I was also told that this engineering team has been known to call the customer to get more information at times. I hope that someone does call me because if they do figure out what the problem was, I'd really like to know myself for some closure on the issue.

My suspicions are the CPU or logic board.

The only times it would not freeze up is when I had music playing through iTunes. It seemed that if the CPU wasn't performing any user initiated tasks, that is when it would freeze. But as long as I had iTunes running, it was fine. It's like the CPU when idle would hiccup or something and forget what to do... I don't know. I figure the store was only able to replicate it once where I was able to replicate it many times a day because they had the machine under stress the whole time whereas it is idle most of the time when I have it. Temperature was never an issue and it was always around 115 F.

A big thank you goes out to Apple and the generous employees at the Partridge Creek store for taking care of me and offering me a new replacement.

So you see, Apple does take care of it's customers.

 

[S.B.G]

Another Update

The new iMac that Apple ordered for me to replace the new refurb I had came in last night and I learned another distinguishing factor between new and refurb iMacs. The new iMac box shows a giant picture of it and has the Apple logo on it. The refurb box was just plain white with no markings except for the shipping labels. I really didn't remember what the box to my iMac 8,1 from 2 years ago looked like.

Anyway, I unpacked it, looked it over and it looks flawless. I replaced the 4GB RAM from Apple with my 16GB RAM from OWC and then finished taking the plastic coverings off of it and hooked everything up. Turned it on and transferred all my stuff from Time Machine which took about 5 hours for 460GB over USB 2.0. This would have been a great time to have Light Peak [Thunderbolt] technology to do the transfer. I wonder how much time I would have saved. (I prefer to call it Light Peak as I think Thunderbolt sounds too corny)

I have no bad news to report so far as it hasn't locked up or frozen on me yet and that makes me feel better.

Again, I have to hand the Apple Store at Partridge Creek in Michigan a big thank you and loads of gratitude for overriding company policy and replacing my new refurb with a brand new iMac. I never mentioned or asked for that level of service and they instead offered it to me.

Being a polite and respectful customer pays off.

Thank you

 

[S.B.G]

Now that I have the new iMac, I've noticed another difference that may be a clue as to why the refurb kept freezing up. The refurb's idle temp was always around 115-125F while this new one of the exact same specifications is running at 95-100F. That is the same temperature range that my 24" C2D iMac runs at.

It just seems odd that two iMacs, of the exact same spec had such a wide difference in idle temperature.

 

[Chorny]

Now that I have the new iMac, I've noticed another difference that may be a clue as to why the refurb kept freezing up. The refurb's idle temp was always around 115-125F while this new one of the exact same specifications is running at 95-100F. That is the same temperature range that my 24" C2D iMac runs at.

It just seems odd that two iMacs, of the exact same spec had such a wide difference in idle temperature.

My first thought reading this thread is that the heatsink was not properly 'bonded' to the CPU.
Glad Apple came through in the end but I wonder what they were really doing with the mac for those first 9 days.