With all due respect to pauloagomes.net, there are a few inaccuracies in the post including the idea that there is any longer a debate about whether SMC fan controller can stop this problem and that the title of the page refers to late 2009 iMacs when the problem actually covers a wider time period. Also, the solution provided asks the user to go into a UNIX shell and execute 'mv', 'chmod', and 'chown' commands including some file specifications that use wildcards which I think may be intimidating and dangerous to non-technical iMac owner. And finally, we all owe props to Krysztof Turek who discovered the fix and I think any solution needs to mention that.
That said, the real reason for my post is to try and reduce the pain that folks experience even after they find this thread. To do that we need to state and restate certain things clearly:
You only have this problem (meaning the one that this thread can help) if you have an ATI Radeon Graphics card (go to About This Mac -> More Info) and your machine was most likely purchased between late 2007 and late 2009. It would help if we could find the earliest/latest models. I know I'm "Early 2008" and I've definitely seen late 2009. Anybody outside those bounds, please weigh in.
If you have this problem, the only solution proven to work is the Krysztof Turek kext fix which allows your system to use an earlier version of the drivers for your graphics card. It works very well. If you correctly execute the kext fix and you still have a problem, it isn't this one.
*IMPORTANT* - Apple is not going to fix this problem. Period. Ever. Period. Stop wondering whether that update is going to help -- IT IS NOT.
When there is an OS X update, it will include drivers. They may not always be newer than the ones you had but they will always be newer than the ones you need and your system will try to use them. So, after an OS X update, you must fix your machine again.
The good news is that, since Mavericks, the driver files have been renamed and now begin with 'AMD' instead of the old 'ATI'. As a result, an OS X update will no longer overwrite your old drivers but will most certainly replace any new ones that you've moved our the Extensions directory. What does this mean? It means that if you've applied the kext fix before, you should not need to run kext_helper again. All you should have to do is remove the appropriate 'AMD' files from the Extensions directory and reboot.
The bad news is that Apple is in the process of tightening up security on extensions and there may be a point where Mac OS will no longer accept and run these old extensions. They have already indicated that this is the direction in which they are moving. When those security changes happen, unless someone can figure out how to appropriately sign the kexts, i.e. imbed a validatable certificate, we will reach the point where, as a group, we will no longer be able to upgrade our OS. I'll ask all tech savvy participants to be on the lookout and notify this thread, hopefully in time to avoid forcing a lot of full system restores.
If you are hitting this thread for the first time and want to try the kext fix, see the guide on page 102.
