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

As reported in an earlier part of this thread. I have ordered a new GPU (at a cost of £134) having been stuck on 10.6.2 for well over a year.

I decided to upgrade anyway to 10.6.7 but then iLife11 would not install due to a license issue (bug). This is resolved in 10.6.8 which I am now running at.

The system ran fine for a few days but then the hangs returned, I did read that the Kext fix does not work on 10.6.8 so I am stuck here now. I have had one lock up every couple of days or so. Seems far more likely to lock up if the system has been used for longer (heat?).

This weekend it is going in for the GPU replacement which I am hoping will fix the problem, especially as this is at my own expense and my current iMac does not seemingly have a hardware issue!

The Kext fix DOES work in 10.6.8 -- if your iMac is capable of booting into 64-bit mode. If your iMac can boot only into 32-bit mode, then the Kext fix won't help with 10.6.8. I believe it is the iMac 7,1 model that cannot boot into 64-bit mode. The iMac 8,1 model (which I have) can boot into 64-bit mode -- so the Kext fix works.

I have two iMac7,1s, both running 10.7.3 with the 10.6.2 ATI kexts. they work perfectly. so did they with 10.6.8.

just go ahead with the kext fix.

Yep, I confirm this (for ATI GPUs). I also have an iMac 8,1 with 10.6.8 running in 64-bit mode with the 10.6.2 Kexts almost a year now.

FYI: I have an iMac 7,1. I've been running with the kext fix on OS10.7.3 for several months now without a problem.

Hello guys,

This is interesting I am sure I read earlier in this very lengthy thread that there was a kernel panic encountered with 10.6.8. Mine is an iMac8,1 so capable of bootimg into 64 bit mode.

Tempted to give it a go, I really dont want to spend £134 un-necessarily.

Many thanks for that.

Yes, if I remember correctly on my iMac8,1, 10.6.8 when used with the kext fix while running as 32 bit gives the kernal panic. I changed my iMac8,1 to 64 bit and used the kext fix with no problem. But since then, new GPU and Lion with standard Lion kexts and no problem either.

Remind me again what your original GPU was? What was it replaced with?

Just to give you reassurance, goskip40, I also have an iMac 8,1 (with ATI Radeon HD 2600 Pro) running 10.6.8 in 64-bit mode with the kext fix, and it has worked fine for me. I think the only real downside is that whenever you (or someone else) upgrades OS X, you have to re-apply the kext fix.

(I do have a problem where the screensaver won't always start when it should, but I don't think it's related to the kext fix or anything.)

Good luck!

Many thanks indeed Brian (and TK111). I am tempted to do this. The other day I dropped the Kext files to my desktop in readiness and then found the bit in the thread about issues with running on 10.6.8

As mentioned I am on an 8,1 system. Have you guys set your systems to boot into 64bit mode by default? Just wondering if the system is likely to panic if it defaults back into 32 bit mode. I guess at that point you can reboot back into 64 bit.

Many thanks again - it is appreciated.!

My original GPU was ATI Radeon HD2600 Pro replaced with the same.

I would switch your system permanently to 64 bit. As far as I know (not that far, maybe) there are no downsides to that. I can't remember how to do it, though, whether I saw it in this thread or not, but a google should turn up the procedure. It's a simple thing.

Looks fairly straightforward, this link explains http://support.apple.com/kb/HT3773?viewlocale=en_US&locale=en_US

I have booted into 64 bit mode now just to ensure system is stable.

Well got my kext fixes in place now. I did have one more hang today prior to install. One moment of panic, the system hung on reboot, I dont think the kext helper was responding as I did a kill on the pid for it in the end and the system booted cleanly.

Thanks guys again for assistance.

Having done the kext fix originally back in early 2011, going to 10.6.6 and having NO freeze ups since then, I decided to move on to 10.6.8 today. I made a very serious error in not checking whether my 8,1 iMac was 32 bit or 64 bit before changing the kext files, which I had saved in a folder from the previous time. So when I rebooted after using kext helper to change the files I got the grayed out screen telling me to restart which I did and it reappeared every time I tried to restart...I though I was screwed.

My solution was to reboot using my original 10.6.1 disc and with that I was able to use my back up mirrored hard drive to start up from. When I got in to that I was able to then get into the internal hard drive and go to the terminal program in utilities and type in the code to switch my computer to 64 bit, which I found online. After that all has been well. What a relief.

I had been holding off and it was only this week that I finally saw enough evidence from forum posters to convince me that the move to 10.6.8 had been totally successful for them. Next upgrade will be to Lion. Not for while though.