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Late 2007 iMac 20" Freezes completely random.

success?

Just a quick update for those of you playing at home... I successfully upgraded to 10.7.4 and re-installed the 10.6.2 kexts and everything seems to be running fine. Three days, no hangs. Hopefully this is the road to recovery.

Thanks for all the help.
 
I wanted to chime in here too. I've been following this topic for 6-8 months and finally decided to give the kext replacement a try.

I'm on a 24" 8,1 iMac 2.8GHz ATI2600 with 6GB of RAM running ML 10.8.1. I've had these "black screen" type of crashes roughly every other day for months. My son, who games on a 20" 8,1 iMac 2.66GHz ATI2600 with 4GB of RAM on Lion also experiences these crashes as well, but his will crash multiple times a day. I had installed smcFanControl on both machines some time ago and it seemed to actually stretch out the time between crashes when running the fans at high speed, but it didn't eliminate them.

Six days ago I swapped out the suggested kexts (ATI2600Controller, ATIFramebuffer, ATISupport) with ones from 10.6.2. I also set smcFanControl to the "default" fan speed, which basically puts the fan speed control back on "automatic" and runs at the speed the system tells them to (very slow). I am happy to report that neither machine has experienced the "black screen" lock up / crash since installing these kexts and rebooting. Again, my son's machine would only go a few hours while he is gaming, and it is now running 6 days straight without a crash or reboot.

Just wanted to pass this on to anyone contemplating the kext swap. It is easy, painless and it works! Thanks to all who found this fix and pointed us to the appropriate websites/blogs on how to do it.
 
For anyone that cares, I was having the frozen screen issue yet still was able to move the cursor. I was debating replacing kexts but was concerned about screwing something up. I ended up pulling one memory bank at a time and isolated a bad memory bank. I've since replaced the bad bank and am back up and running with no freezes and no kext modifications.

I'm on a 24" iMac 8,1 with a 3.06 gHz processor and an nVidia 8800 GS GPU running 10.8.1. I saw freezes in every OS since 10.5.
 
Sped said:
For anyone that cares, I was having the frozen screen issue yet still was able to move the cursor. I was debating replacing kexts but was concerned about screwing something up. I ended up pulling one memory bank at a time and isolated a bad memory bank. I've since replaced the bad bank and am back up and running with no freezes and no kext modifications.

I'm on a 24" iMac 8,1 with a 3.06 gHz processor and an nVidia 8800 GS GPU running 10.8.1. I saw freezes in every OS since 10.5.
Click to expand...

You have a Nvidia 8800. This thread and most people in it are those that have an ATI 2400/2600. The two problems are not the same and are not caused by the same thing.
 
Intell said:
You have a Nvidia 8800. This thread and most people in it are those that have an ATI 2400/2600. The two problems are not the same and are not caused by the same thing.
Click to expand...

I guess my point is that memory was the problem and not the GPU or the kexts.
 
As an update/confirmation: I updated a family member's 20" 7,1 iMac to 10.7.4 recently; froze as it always had (10.6.2 was the last solid OS with zero freezing) until I did the kext swap (ATI2400Controller in my case, ATIFramebuffer, ATISupport). It has been going on a week with no issues.

I have not tried the 10.7.5 update yet to see if the video kexts are replaced again; guess I could download and check it out with Pacifist first. Can anyone confirm if the kext swap has to be reapplied or the unlikely possibility that it solves the problem without it?
 
Both 10.7.5 and 10.8.2 have new kexts that could solve the freezing problems. The change dates on some are as late as the 11th of September. The Snow Leopard security update does not have any new kexts.
 
I tried the 10.6.2 kext replacement on mine, but it would no longer boot afterward. It would just crash on boot. Anyone know why?
 
Me too

Hi, I have been reading this thread for the last few days and experimenting on my iMac with the various suggestions.

I need to keep on MacOS 10.6 (preferably 10.6.8) and have tried the fix by installing the three kext files ATI2400Controller.kext, ATIFramebuffer.kext and ATISupport.kext from the 10.6.2 Update using Kext Wizard into 10.6.8 but I also had Panics on start up (with those extensions mentioned in the panic) I have since restored to 10.6 (copied the extensions folder) and now just updated to 10.6.2.

From my experiences with this iMac the instability seems to happen when I go past 10.6.2. What is the last iteration of 10.6 I can run with the kext files from 10.6.2. As I said 10.6.8 doesn't seem to work as it has been mentioned something about 64Bit, can I go to 10.6.7?

I have read this forum and other ones around by clicking links and I can't seem to find a definitive answer, sorry to keep on!

Thanks
Simon
 
I wondering if it is possible just to reduce the workload on the graphics card. I only use mine for web surfing and the occasional netflix. Is there a way to change the settings to take the workload off the graphic card? or would that not resolve the problem?

By the way, I got mine to boot again by putting the original kext files back. That goodness I have a Tiger partition to fix things with.
 
Try using the 10.6.6 kexts first. They are newer and more stable then then 10.6.2 ones. They should fix most problems. For the few that are still having crashes, use the 10.6.2 ones. There is no way to reduce the GPU load besides not playing games or never using the machine. Even by not using the machine, it'll still crash when the screen is off.
 
Update

Just updated my iMac to MacOS 10.6.6 and had a look at the Kexts before I changed them for ones from 10.6.2 and interestingly the kexts in 10.6.6 are version 1.6.26 Created/Modified etc 03/08/2009 and the kexts that I extracted from 10.6.2 are version 1.6.6 Created/Modified etc 03/11/2009 so a later version in a previous version?

Hmmm.....
 
Sorry to keep on..

I have tried everything that others seem to have succeeded with but can't get it to work.
I consider myself to be fairly able to do this sort of thing but its just not happening.

I have tried installing the 10.6.2 kexts in 10.6.8 and get a panic on start up
& 10.6.6 kexts in 10.6.8 and also get a panic on start up - both using kext wizard to repair permissions and rebuild cache after each installation.
also
it seems that I will have to leave my iMac running 10.6.2 from now on? As I mentioned in an earlier thread I need to be running Snow Leopard for my apps - preferably 10.6.8 for the App store etc..

Cn anyone shed any light on my circumstances?
Thanks - in advance
Simon
 
Same thing happening here Simon.

Every time I get a freeze I look at the error console for the cause. Each time, I would google the error and try to correct. After numerous corrections I concluded that a lot of these minor errors probably had nothing to do with the freezes. They just seem to be random events that were coincidental to the freezes.

I finally ended up installing another 10.6.8 system on an external drive. I use the external drive for repairing the permissions on my internal drive after a freeze because it seems to do a more thorough job than running the repair from the same OS. It's also faster than using the install disk. I can usually go four or five days, using this method, before I have a another freeze.

I have only found two things that consistently cause a freeze - the Apple scanning utility and Time Machine (if it tries to auto launch while the mac is in sleep mode).
 
mid 2007 iMac Freezes but runs fine in Safe Boot Mode

I am now a member of the frozen iMac club, I have seen many people with similar issues as myself however no one seems to mention that there computer runs perfect in Safe Boot mode. Is this a promising sign or expected?

I bought the computer with Lion OS on it as well as SMC fan control (obviously the previous owner had heating issues). I was also suspicious of 6GB of ram considering the age of the computer. 1 - 2gb chip and 1-4gb chip.

Upon using the computer it began to freeze at random intervals usually after being asleep

I did a fresh install of Lion, and did a complete wipe of the hard drive (computer still froze)

I then experimented with each RAM chip (running each independently in the system) I still encountered my system freezing.

When i say freezing my mouse still moves but has no clicking ability. I am usually doing something very basic google search etc.

I have since reloaded Lion again, repaired the disk in disk utility but still encounter freezing.

The one positive thing is that if I operate the computer in safe mode it appears to function perfectly. Is there anyway to diagnose the issue from safe mode?

Any help would be greatly appreciated.

THANKS!
 
It operates fine in Safe Mode because the ATI kexts are not loaded and thus do not cause any crashing.
 
Intell, how would I fix the problem? What is ATI kext? Is there some type of update or modification I need to make?

Thanks
 
The kexts that you need to replace are listed in the thread. Even on just the last two pages, you should be able to discover which ones.
 
10.7.5; no kext replacement..

Just a heads up...I did the 10.7.5 update, but have *not* re-installed the 10.6.2 kexts. Going to let it run this way for a while and see what happens. Will keep you posted. It would be great if the new kexts fixed the problem.
 
rastriffler said:
Just a heads up...I did the 10.7.5 update, but have *not* re-installed the 10.6.2 kexts. Going to let it run this way for a while and see what happens. Will keep you posted. It would be great if the new kexts fixed the problem.
Click to expand...

OK, well that didn't take long. Computer froze up in the first 30 minutes. Had to re-install the 10.6.2 kexts. Seems to be working again; I'll post if it doesn't.

So apparently, the 10.7.5 update does not fix the kext problem. 🙁
 
rastriffler said:
OK, well that didn't take long. Computer froze up in the first 30 minutes. Had to re-install the 10.6.2 kexts. Seems to be working again; I'll post if it doesn't.

So apparently, the 10.7.5 update does not fix the kext problem. 🙁
Click to expand...

I have a feeling they will never fix it..
 
iMac Freeze FIXED!!!

3 months of frustrating random freezes, my iMac (late 2006 17 inch) passed all
Apple Genius Bar and TeKServe diagnostics. A new external firewire drive, and removal of all peripheral drives, and it still froze.

I installed smcFanControl (free download), set all fans to around 3000, and
I have not not had a freeze since!!!!

Theory from numerous web searches: video card overheats, gets iffy connection, cooled by increased fan speed.
 
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