Q: 24" iMac Screen Freezes since 10.6.3 update - pls help!

Go to page 28.  This discussion has not determined that Lion will fix this.  And 10.6.8 is a problem.  Read the relevant discussion.  Again, if you have the freeze that is primarily discussed here, the fix works.

P.S., a kext is a "kernel extension" and the ones we're concerned with are the "ATI graphics drivers." The Apple genius people I talked with on several occasions were apparently not aware of our problems either, but thankfully we have this resource (if that turns out to be what's troubling your system, too).

spokes46 is right, 10.6.8 apparently requires that you set your system to 64bit kernel, which is also discussed in this thread. I did that and it works. Otherwise, sticking with 10.6.7 and the kext fix is the simplest solution.

spokes46 wrote:

 

Go to page 28.  This discussion has not determined that Lion will fix this. 

vexbit reported that the golden master fixes the problem. So why not just wait for Lion?

Until we get some more people saying Lion fixes this, I'm worried.  Others Lion testers have reported that Lion did not fix the freeze.

As to why not wait, that's up to the individual.  I was sick of my machine freezing at critical moments at work.  If someone can live with the restarts and don't have to worry about potential loss of work, meetings, etc., that's cool.  But I haven't had a freeze in months – and it feels good.

I found out that if you start up your mac and hold down the 6 and 4 keys until you see the apple logo, it will boot into 64 bit mode. I checked and it did just that. I've had no issues so far.

Eclipsethegalaxy wrote:

 

I found out that if you start up your mac and hold down the 6 and 4 keys until you see the apple logo, it will boot into 64 bit mode. I checked and it did just that. I've had no issues so far.

That's true. Did you check in the System Profiler under “Software” if this was succesful?

And please note that the change is not permanent.

Yes it was successful, and yes I know it's not permanent. However I understand Lion will boot as 64 bit.

Hello all!

Well, it's been a long haul with this problem and I'm still very thankful to the original 10.6.2 ATI2600 KEXT replacement solution. Without it I would have chucked this iMac in the trashcan several months ago. Like most of you, it was freezing three to four times daily with either a solid white screen, a solid black screen, or a white screen with vertical lines.

I've been keeping an eye on this forum for more solutions to emerge and have developed what I hope to be a good theory. Let me explain:

• I've been operating off of 10.6.7 for a few months or more now with the 10.6.2 ATI2600 KEXT replacement strategy and it's been flawless. iTunes has hung once on me, but I blame iTunes for that.
• I've been following the brave few who have upgraded to 10.6.8 and attempted (and failed) to install the 10.6.2 KEXT files (resulting in a kernel panic)
• It sounds like the only people that have gotten it to work have been those that upgraded to 10.6.8, switched to 64 bit kernel mode, and then applied the 10.6.2 ATI2600 KEXT.

So, here's my idea: What if the problem only expresses in 32-bit kernel mode, and that as of 10.6.3 there was an issue with the 32-bit version of the ATI2600 KEXT, but not the 64-bit version? It seems like the 32-bit and 64-bit video drivers would be slightly different and possibly not susceptible to the same problems. On PC's at least, 32 bit drivers are always packaged (and compiled) separately from 64 bit drivers. Granted, if the bug is in the source code itself, it might be a moot point.

So this is what I did today:

1. Made sure I had a good backup.
2. Upgraded from 10.6.7 with the 10.6.2 ATI2600 KEXT file replacement to 10.6.8 using the normal "Software Update" approach and then rebooted.
3. Verified that the KEXT file located at iMac > System > Library > Extensions > ATI2600Controller.kext was a newer version than the 10.6.2 KEXT (it was: 1.6.36, dated 3/25/2011, 737KB)
4. Verified that the KEXT file located at iMac > System > Library > Extensions > ATIFramebuffer.kext was a newer version than the 10.6.2 KEXT (it was: 1.6.36, dated 3/25/2011, 344KB)
5. Verified that the KEXT file located at iMac > System > Library > Extensions > ATISupport.kext was a newer version than the 10.6.2 KEXT (it was: 1.6.36, dated 3/25/2011, 3.4MB)
6. Changed the Kernel driver mode to 64-bit and then rebooted
   -- From Terminal: sudo systemsetup -setkernelbootarchitecture x86_64
7. Verified that after reboot OS X was truly running in 64 bit mode (http://support.apple.com/kb/HT3770)
8. Tried to tax the Video card and force it to crash by playing 3D-intensive games and long movies in Quicktime.

So far (about 6 hours into the experiment), I'm cautiously optimistic because I haven't had any freezing or crashing. However, I won't be confident that it's resolved until I've gone at least two or three days without incident.

I'll let you all know if it's successful (or not). Fingers crossed.

: Tyler

Vexbit, can you confirm the versions, dates, and file sizes of the following three files in the Lion GM?

1. iMac > System > Library > Extensions > ATI2600Controller.kext (for reference, in 10.6.8 it was: 1.6.36, dated 3/25/2011, 737KB)
2. iMac > System > Library > Extensions > ATIFramebuffer.kext (for reference, in 10.6.8 it was: 1.6.36, dated 3/25/2011, 344KB)
3. iMac > System > Library > Extensions > ATISupport.kext (for reference, in 10.6.8 it was: 1.6.36, dated 3/25/2011, 3.4MB)

Thank you!

OK, tylerted, this is what I understand from your post: You're running 10.6.8 in 64 bit kernel mode with the ATI kext files that came with 10.6.8 from Software Update.

I did that, too, and was okay for a day but got nervous and reverted the kexts to their 10.6.2 versions. If you get a freeze on your new setup, please let us know.

Lion GM Kext

ATI2600Controller.kext - Version 7.2.9 - 686kb - modified June 24

ATIFramebuffer.kext - Version 7.2.9 - 300kb - modified June 24

ATISupport.kext - Version 7.2.9 - 3,5mb - modified June 24

I didnt have a problem for a couple of days now, so i hope its finally fixed

LION is out now in Mac App Store!

Install and try LION without using the kext files from 10.6.2 to see if it still freezes! 

Just as an update, it's now been about three and a half days since I updated to 10.6.8 and switched to 64-bit kernel mode without replacing the KEXT files, and my 8,1 24" iMac hasn't crashed once

: Tyler

I will be most interested to learn what your and other people's continuing results are with Lion and a 7,1 imac. The 7,1 imac does not support the 64-bit kernel, so the 64 bit kernel solution is not available to the owners of such machines.

I am running 10.6.7 with the kext fix, was hesitant to run the 10.6.8 update because of the problems reported on this thread about the kext fix not working.

Please keep us posted!