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

Thanks very much, Dmaude!

Success on 10.10.3.

Well, eventually.

From 10.9.5, installed 10.10.3, had an almost immediate freeze. Had to press power button to restart. After restarting, quickly deleted and installed the needed kexts, and ran sudo nvram boot-args=“kext-dev-mode=1” from Terminal. Tried to restart but disk activity would not stop even at black screen so I hard restarted again. Kexts did not load.

Edited the /Library/Preferences/SystemConfiguration/com.apple.Boot.plist <key>Kernel Flags</key>

<string> </string> to <string>x86_64 </string>, tried to restart, same thing, hard restarted, and kexts did not load.

Installed kexts again, thinking that the installation failed. Tried dmaude’s routine of chmod -R 755 ATI2400Controller.kext etc. but got error chmod: ATI2400Controller.kext: No such file or directory.

Tired changing permissions on the files directly giving wheel R/W, restarted, kexts did not load.

Got rid of x86_64 and edited boot.plist, adding kext-dev-mode=1 instead. Restart again. Kexts did not load.

In System Report Extensions I saw the kexts were there but not loaded: Kext signature validation error code -67061

Finally for the 3rd time after a successful restart, edited boot.plist again, emptied the <string> </string>, like it was originally, and ran sudo nvram boot-args=“kext-dev-mode=1” again from Terminal. Entered password, restarted, and glory be, kexts loaded and all is good.

What would be wonderful is if some developer would get a Kext signing certificate from Apple so these kexts would work in future iterations of Yosemite. http://stackoverflow.com/questions/26830800/cant-sign-kext-in-mavericks-yosemite

Thanks for sharing, Djeffrey, but could you please clarify what new steps has one to take to make the kexts work in 10.10.3?

Thanks in advance,

Mikołaj

I don't know if there are any new steps needed for 10.10.3 than for 10.10.0 and up. The main thing to make it work and the kexts to load in Yosemite seems to be the Terminal command: sudo nvram boot-args=“kext-dev-mode=1”

In my case, this did not work the first time, but I was not able to restart the computer without pressing the power button either, so I can't say what will happen with anyone else's system. When I was finally able to restart from the apple menu, the kexts loaded and the comp seemed fine.

Before I updated to 10.10.3, I checked the disk for errors, repaired permissions, removed some older apps, and rebooted once in safe mode to generally clean up.

One caveat though... I have been noticing occasional artifacts on the screen, sort of checkerboard looking pixely areas, which used to be (while still in Mavericks and before I ever tried the kext fix) a signal that a freeze was about to happen. But, so far, I have not had any freezes in 10.10.3.

Tazthed, Thank you for the reply with the instructions!!! Belated. I never got a chance before.

Have not dared migrate to 10.10 yet, but will save the instructions for now.

Thanks again

Hi everyone,

I finally decided to tackle this issue with my Mid-2007 2Ghz 20inch iMac. (ATI HD2400XT)

I can't get the fix to work on 10.10.3

This is what I did step by step:

1. Clean install of Yosemite from USB Stick.

2. Downloaded the 10.6.2 ATI kext files and the KextHelper

3. Ran the sudo nvram boot-args="kext-dev-mode=1"

4. Put the 3 Kext Files in Library/System/Extensions (Error Message saying could not be installed)

5. Put kext files on desktop and dragged them into KextHelper and let it run. (ok)

6. Reboot

It still freezes regularly.

Questions:

A) Did I do something wrong or did I miss something?

B) When I typ kextstat in the Terminal, it shows all installed kexts. In this list, it still shows the AMD2400Controller. The ATI kexts are not listed. Does this mean it doesn't let me replace them?

Any help would be greatly appreciated. My mom had this freezing issue for years and I really want to fix it for her.

Thanks!

I think you missed 2 things... you should remove the AMD kexts, and then run sudo nvram boot-args="kext-dev-mode=1" after you drop in the ATI kexts.

1. Create folder on desktop called kext bu.
2. Copy System > Library > Extensions files AMD2400Controller.kext, AMDFramebuffer.kext, AMDSupport.kext and paste them there.
3. Delete originals.
4. Open KextDrop. or Kext Helper if you prefer.
5. Give permission in Security and Privacy if the program is from “unknown developer”
6. Drop in ATI2400Controller.kext, ATIFramebuffer.kext, ATISupport.kext. Click Install. Close KextDrop
7. Run Terminal command: sudo nvram boot-args="kext-dev-mode=1"
8. Restart.

Happy Mother's Day don't forget.

With the new "Metal for Mac" graphics performance feature of OS X El Captian... maybe our issue will finally be solved.

It looks like El Capitan won't make a difference, as Metal for Mac will run only on machines built in 2012 or later:

http://www.imore.com/here-are-macs-work-os-x-el-capitans-metal

I am posting again for people having the same issue:

We have a fix for this!

System Freezes Randomly after 10.6.3 Update

check it out

> It looks like El Capitan won't make a difference, as Metal for Mac will run only on machines built in 2012 or later:

> http://www.imore.com/here-are-macs-work-os-x-el-capitans-metal

Maybe not so fast (preface: I am successfully running the Turek [+ others] fix using only Yosemite 10.10.4, not

El Capitan public beta 2 yet, using a mid-2007 20" iMac with AMD Radeon 2400XT.

However, I do wonder about the following possible caveat, indicating that El Cap / 10.11 may only honor

*signed* kext replacements, per:

http://www.macworld.com/article/2948140/os-x/private-i-el-capitans-system-integr ity-protection-will-shift-utilities-func…

So the $64K question is whether "Signed by Unknown" good enuf for El Cap?

Braver folks can try, thence to report back ...

--retiarius

P.S. It still is sad that, by not fixing this driver bug, Apple has sent thousands of perfectly decent

iMacs to Goodwill, landfill, or points beyond, because regular users are not hip to the heroism exhibited here.

I remain embarrassed by Apple not being able to quash a regular system-killing bug while simultaneously advertising that

this machine is "10.11 ready".

If anyone is still here... 10.10.5 nuked my ATI kexts and loaded the AMD ones... again. It seems that simply running sudo nvram boot-args=kext-dev-mode=1 in Terminal while logged in as my username does not work anymore.

What does work is booting in single user mode: press Command (⌘)-S at the startup chime, hold it down till the black screen with white text appears. After a while the mac is booted, hit Enter to get to the command prompt # and then type sudo nvram boot-args=kext-dev-mode=1, hit Enter, type exit to reboot.

Try running the kext fix while logged in as root user and don't forget to log out of root user when done.

Excellent tip, will try it the next time... for 10.10.6? Fingers crossed for El Capitan.

Hi Djeffrey,

First of all, THANK YOU SO MUCH for clarifying the procedure for me a while ago. The Mac was 100% Crash free for weeks. It was like a dream.

Now I have the same issues you recently described. Apple replaced my ATI kext files with the Update.

I tried to follow your instructions by copying the kext files and installing them with Kext Drop. Then I went into Single User Mode and typed sudo nvram boot-args=kext-dev-mode=1

Before rebooting, it briefly said something like "kext file installation failed", rebooted and crashed again.

Would you be so kind and advise me again on what the exact steps are to make it work? Greatly appreciated!