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

I'd wait until the .2 or so update. It's never the best idea to dive in with an .0 release.

I'm running Yosemite without the fix to see how it goes. I usually took a week or two before I saw issues in the past (usually at the most inopportune time), so I'll report back if anything happens.

mine just froze.

the old kexts will not load, cause Yosemite has kext signature checking enabled, and the 10.6.2

ones obviously have no valid signature. so if you remove the new AMDxxxx kexts you are left

with sw only graphics, which is painfully jerky.

disabling kext signatures is possible, i just did this, and the old kexts booted perfectly.

you have to edit this file: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

there is a "Kernel Flags" key, and an empty <string></string> value. you have to type

kext-dev-mode=1 between the string markers, and save the file. to do so, you require administrative

credentials. it can be done from terminal, but a regular text editor works as well.

don't you screw up the file, or your mac may not be able to boot easily.

depending your current configuration or hardware, the file may contains other sections, whatsoever.

those need to be left intact.

warning: this stuff disables osx10.10's kext security measures, so basically any proper kext can

be loaded. yes, even ones, that contain malicious code or stuff like that. so choose your kexts

wisely. nevertheless, there wasn't any kext-security before yosemite anyway.

Should you not have the original files from 10.6.2., there's an easy way to extract them from the

apple system updates as long they are available for download.

the boot file:

$ cat /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<plist version="1.0">

<dict>

<key>Kernel Flags</key>

<string>kext-dev-mode=1</string>

</dict>

</plist>

os version:

$ uname -a

Darwin crowley.local 14.0.0 Darwin Kernel Version 14.0.0: Fri Sep 19 00:26:44 PDT 2014; root:xnu-2782.1.97~2/RELEASE_X86_64 x86_64

loaded kexts:

$ kextstat | egrep 'ATI|AMD'

104 2 0xffffff7f8222f000 0x45000 0x45000 com.apple.kext.ATISupport (6.0.6) <66 12 11 7 5 4 3 1>

105 0 0xffffff7f82274000 0xca000 0xca000 com.apple.kext.ATI2400Controller (6.0.6) <104 66 12 11 5 4 3 1>

106 0 0xffffff7f81850000 0x233000 0x233000 com.apple.ATIRadeonX2000 (10.0.0) <66 12 7 6 5 4 3 1>

108 0 0xffffff7f8233e000 0x12000 0x12000 com.apple.kext.ATIFramebuffer (6.0.6) <104 66 12 11 7 5 4 3 1>

swmaster: Thank you for your post.

Can you see if this is correct - I want to make it easy for others.

1) Install Yosemite OS X.

2) Install the 3 original kext ATI files from 10.6.2 with the Kext Helper.

3) E*** this file: /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

by typing:

kext-dev-mode=1

between the <string></string> markers, so it looks like this:

<dict>

<key>Kernel Flags</key>

<string>kext-dev-mode=1</string>

</dict>

4) Save the plist file.

5) Reboot your computer. Done!

-------------------------

Question: what does "kext-dev-mode=1" mean?

Hi Tazthed,

yes, you nailed it. this is the process.

kext-dev-mode=1 enables to load unsigned kexts, thus the old ones we (or better said our oldie radeon 2x00s) like :-)

i'm quite sure someone will just put together a click-click app for all this.

one note though: as it is owned by root (and shall remain so), 3rd party editors from app store may not be able

to modify it. for example textwrangler fails if you try to save anything that requires admin password, like this

file. this is a rule enforced by the app store. you can read more about this here:

http://www.textwrangler.com/support/bbedit/auth-saves.html

TextEdit even refuses to open the file.

so the easiest way for a bit experienced users is to do this via Terminal and sudo+vi.

Okay thanks swmaster ;-)

It sounds complicated with the Terminal. I hope that someday someone will find an easier solution to his freezing issue on Yosemite.

just checked, there's a one-liner, which does the trick:

open Terminal, and type at the prompt:

sudo nvram boot-args="kext-dev-mode=1"

OSX will prompt for your password, enter it, characters will not be echoed in Terminal.

then close Terminal and reboot, and you are good to go.

this does not modify the above mentioned file (com.apple.Boot.plist), it does the modification in the nvram.

but the result is the same.

Cool! I will try it when I have made a backup and installed Yosemite. Thanks swmaster!

I have been a long follower of this thread.

I have a mid-2007 20-inch iMac that has been suffering from this issue for many years now. Mine is best described as the freezing issue where the mouse still moves and audio keeps playing but nothing else can be done without a hard reset.

Up until recently I had been applying the kext fix successfully to remedy the problem.

I decided to investigate Yosemite's effect on the issue..

I was pleasantly surprised to find that after installing 10.10 I had zero freezes for a several days. I never used to make it more than a couple minutes after rebooting. Mind you, my iMac is no longer my main system and now only works under a very light load (web browsing, video streaming, etc). However, today I tried plugging in an external bus powered firewire drive. After mounting the drive and then opening an audio software program, my system froze for the first time under Yosemite.

It was at that point that I took the usual steps and applied the kext fix, deleted the AMD extensions, and edited the com.apple.Boot.plist file (which was a new step for me).

The first issue I noticed after the kext fix was very laggy and choppy picture quality. The mouse movements weren't smooth and everything seemed to struggle. After applying the "kext-dev-mode=1" fix and rebooting, the lag seemed to be resolved. However, I ultimately ended up losing my 2nd display via the midi-DVI connection as well as finding several small display issues such as: no program names showing up when you hover over the icons in the dock, choppy text and icons in stacks in the dock, and some other less than desirable side effects.

Needless to say, this was unacceptable performance to me so I re-installed Yosemite and now things are back to normal. Until I push the system harder I suppose..

Obviously this is only my experience, but I felt I should share it with you all since we're still in the early stages of Yosemite with the freezing issue and only a few of us have tested it. Clearly the problem persists so any feedback is welcomed.

7,1 here with 10.9.5 running no freezes. you must run sudo command in terminal to permanently boot in 64-bit run the delete all AMD kexts install ati kexts from 10.6.2. A good fan control is recommend because card still runs warm.

I've been suffering with the screen freeze ever since my 2006 iMac Apple Care warranty expired (and even before ... but Apple never acknowledged the ATI driver issue; just kept telling me to reload the operating system). Anyway, I have been late in learning that Apple is replacing video cards on 2011-2012 27 inch iMacs with a similar problem affecting the ATI video card. ( iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program ) I have been shopping for a new 27" iMac but am now hesitating. Is anyone willing to speculate if there will be a recurrence of these problems with the newest generation of iMacs since Apple never seems to have been able to root out the cause in several earlier generations?

Previously I reported that I had not freezes after upgrading to 10.9.5 and using the stock kexts, unfortunately after a week or so it started to freeze for a handful of times in about 1 month. I noticed that each instance happened when I was using safari.

I have just upgraded to 10.10 and still using the stock kexts, so far no freezes for just 1 day so it is still too early to confirm.

I am using an early 2008 iMac with ATI Radeon HD 2600Pro, ROM Revision: 113-B2250L-259

Hi!

2 weeks without fixing the kexts from 10.6.2 and my imac 2007 has no freeze in 10.9.5.

And yes, my system load the AMD2400Controller, AMDFramebuffer and AMDSupport

I have been running Mavericks 10.9.5 on a iMac 7,1 Core 2 Dou 2.0Ghz 4G Ram for nearly a month with the fix I have created simply by using bits and peaces I have found through out the last 112 pages of this thread. I have created a very detailed tutorial for all those affected iMacs with the ATI 2400 & ATI 2600 Graphics card. Sorry I tried several times to post here but the formating and apple support forum kept timing out on me here.

Go see attachment here:

http://forums.macrumors.com/showthread.php?t=1809500