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

I don't know if this is just coincidence or not, but since updating my iMac to 10.6.3 it keeps on crashing. On 3 separate occasions today, whilst using my Mac the screen has gone completely black with thin white lines down it.....see pic below:

http://picasaweb.google.com/lh/photo/6SYzhCgVYEU5TBKqRfOQ1Q?feat=directlink

The fans and hard disk are still running but it will not respond to any keyboard or mouse presses - I simply have to turn it off by holding the power button in.
It will then restart as usual.

Anyone got any ideas? Do you think that if I was to re-install Mac OS X from my original install disk it could solve the issue?

Thanks

Darren

24" intel imac 2.8Ghz, Mac OS X (10.6.3)

Posted on Mar 31, 2010 2:43 PM

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

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  • by Tazthed,

    Tazthed Tazthed Oct 28, 2014 12:17 PM in response to swmaster
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    Oct 28, 2014 12:17 PM in response to swmaster

    swmaster:

     

    I haven't had time to try your method. Busy at the moment.

    But I would like to know if you experience the same as Teardropcarnival (post above). He uses the 2007 imac:

     

    " 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."

  • by mattwinters78,

    mattwinters78 mattwinters78 Oct 28, 2014 2:15 PM in response to Tazthed
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    Oct 28, 2014 2:15 PM in response to Tazthed

    Tazthed:

    Did you see my tutorial about the 7,1 iMacs and other "Vintage" Macs and their EFI and the 10.6.2 kexts running in a 64-bit environment.

  • by Tazthed,

    Tazthed Tazthed Oct 28, 2014 4:04 PM in response to mattwinters78
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    Oct 28, 2014 4:04 PM in response to mattwinters78

    Yes I saw your very long tutorial... did I miss something?

  • by mattwinters78,

    mattwinters78 mattwinters78 Oct 28, 2014 7:49 PM in response to Tazthed
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    Oct 28, 2014 7:49 PM in response to Tazthed

    Do you think that the 10.6.2 kexts do not load properly in Yosemite even after flaging the Boot.plist with "kext-dev-mode=1" which allows the use of unsigned kext in Yosemite. Because some older macs (7,1 my direct experience) the EFI boots the kernel in 32-bit by default when the running OSX is v10.6? They do not load properly in Mavericks on the 7,1. because the 7,1 booted the kernel in 32-bit when the OSX was v10.6 which is close to 10.6.2 kext the the last known working kext for the ATI 2400 or 2600 Graphics cards. If has worked for Mavericks it may for Yosemite. 

  • by Tazthed,

    Tazthed Tazthed Oct 29, 2014 4:12 AM in response to mattwinters78
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    Oct 29, 2014 4:12 AM in response to mattwinters78

    I have the 8.1 imac from 2008 and I wonder if the side effects also appear when loading the kext in Yosemite on iMac 8.1. Because if it doesn't have the side effects then maybe it has something to do with (like you wrote) the 7.1 iMac booting in 32 bit?

    I just checked my 8.1 iMac and it boots in 64 bit by default. The problem is that I am working on a project at the moment and don't have time to backup and try Yosemite. When I take a break I come here to read about this freezing problem

  • by mattwinters78,

    mattwinters78 mattwinters78 Oct 29, 2014 6:41 AM in response to Tazthed
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    Oct 29, 2014 6:41 AM in response to Tazthed

    I Believe the Xserve is the only Mac prior to 2009 the booted the kernel in 64-bit by default in v10.6. All other Macs are capable of booting OSX v10.6 when told to do so (given they have a 64-bit processor). Some still boot in 64-bit by default but only OSX v10.6 Server. And other Macs like the Mac Book and Mac Pro got a patch to boot 64-bit by default with OSX v10.6. I don't believe that the 8,1 defaults to 64-bit. Did your 8,1 experience freezes in mavericks?

  • by Tazthed,

    Tazthed Tazthed Oct 29, 2014 12:33 PM in response to mattwinters78
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    Oct 29, 2014 12:33 PM in response to mattwinters78

    You are right - iMac 8.1 does not use 64 bit kernel by default, but it supports the 64-bit kernel.

     

    When I check what kernel my iMac  uses in the Terminal I can see that it uses 64 bit.

     

    Yes, my iMac 8.1 had freezes in Mavericks. Then I applied the original kext files from 10.6.2 (and removed the AMD kexts) -> no more freezes. I did not need to tell my EFI to boot in 64 bit.

  • by mattwinters78,

    mattwinters78 mattwinters78 Oct 31, 2014 10:48 PM in response to mattwinters78
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    Oct 31, 2014 10:48 PM in response to mattwinters78

    Sorry there's a bad link in Step 7

    7.The 7,1 iMac, some 8,1 iMacs & other Vintage Macs that are capable booting the kernel  in 64-bit, but whose kernel boots in 32-bit  by default when v10.6(snow leopard) was/is the OSX. I implore you to test my theory in step 8 which may help those early iMac who have the 10.6.2 kexts installed in Mavericks and are still experiencing the freezes.

    If a moderator would like to fix the link and delete this post that would benefit all!

  • by mattwinters78,

    mattwinters78 mattwinters78 Nov 1, 2014 2:42 AM in response to Tazthed
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    Nov 1, 2014 2:42 AM in response to Tazthed

    A 64-bit Processor in a Mac on any version of OS X(except v10.8) EFI can boot a kernel in basically 3 different architectures: i386, 64 & x86-64.

    Prior to 2009 OS X booted every Mac's EFI booted the kernel in i386, except the Xserve by default booted x86-64, and some MacBooks and MacPros after receiving a patch mid way through OS X v10.6(Snow Leopard) defaulted to x86-64.

    • i386 is a 32-bit kernel.
      • A 32-bit kernel can run both 32/64-bit apps, hardware,etc. but only 32-bit kext for apps, hardware,etc will load.
    • 64 is, well, a 64-bit kernel.
      • A 64-bit kernel can run both 32/64-bit apps, hardware,etc. as long as the 32-bit kext are either, replaced or, patched to a 64-bit kext.
        • If not replaced or, patched to 64bit the 32-bit kext for apps, hardware,etc. will fail to load.
    • x86-64 is a Hybrid kernel
      • A Hybrid kernel can run both 32/64-bit Apps as well as 32/64-bit kext.
    • OS X v10.6(Show Leopard) EFI is capable of booting all 3 types but defaults to i386.
    • OS X v10.7(Lion) EFI is capable of booting all 3 types but defaults to i386.
    • OS X v10.8(Mountain Lion) EFI is only capable of booting 64.
    • OS X v10.9(Mavericks) & v10.10(Yosemite) EFI's are capable of booting all 3 types but default to 64.

    Now I know some users have gotten the 10.6.2 ATI kext to stop the freezes in different versions of OS X. The reason for this is the 10.6.2 ATI kexts floating around have been developed into a "hybrid' kext. But, kext can only be written 32-bit or 64-bit. What we know is those kext were originally written in Snow Leopard and then modified by someone in an attempt to be able to load them as 64-bit or "hybrid." Regardless the outcome the 3 kext may say their loaded to a 64-bit kernel but all or some of the coding within each(controller, framebuffer or support) kext may or may not all working properly (freezes, doesn't freeze & overheats then freezes). These kext may be working for some users right now but may not for future versions of OS X and beyond as this has been shown for some users cannot update beyond a certain version of OS X.That all said the way to get the v10.6.2 ATI kext to work is to tell the EFI to boot a x86-64 kernel as described in Step 8 of my tutorial 2 pages back in this tread. But if the kext are flawed then loading the originals in a x86-64(Hybrid kernel) if you can get them may be the best bet. Or better yet if kext from one of the MacBooks or MacPros that had the affected graphics card in them that received the patch mid way through OS X v10.6(Snow Leopard) where patched by apple for a 64-bit kernel.

  • by Tazthed,

    Tazthed Tazthed Nov 1, 2014 2:14 PM in response to mattwinters78
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    Nov 1, 2014 2:14 PM in response to mattwinters78

    Couldn't wait any longer - I just upgraded from Mavericks to Yosemite. I installed the original kext files from 10.6.2 and deleted the AMD kext files.

     

    I added "kext-dev-mode=1" in the "/Library/Preferences/SystemConfiguration/com.apple.Boot.plist"  (thanks to swmaster).


    I rebooted -> No problems! Everything runs smoothly!

     

    I also checked that the original kext files were installed correctly.

     

    Computer model: iMac, 24 inch, from 2008.


  • by mattwinters78,

    mattwinters78 mattwinters78 Nov 4, 2014 6:23 AM in response to Tazthed
    Level 1 (0 points)
    Nov 4, 2014 6:23 AM in response to Tazthed

    Update on your Yosemite install?

  • by Tazthed,

    Tazthed Tazthed Nov 4, 2014 12:07 PM in response to mattwinters78
    Level 1 (0 points)
    Nov 4, 2014 12:07 PM in response to mattwinters78

    It is still running fine. No freezing issues or any graphical issues. Seems like Yosemite is faster than Mavericks.

     

    Just for your information my iMac 8.1 boots in x86_64.

  • by dmaude,

    dmaude dmaude Nov 8, 2014 6:49 AM in response to mattwinters78
    Level 1 (0 points)
    Nov 8, 2014 6:49 AM in response to mattwinters78

    I have a 20-inch mid-2007 iMac with an ATI Radeon HD 2400 XT graphics card. It is currently running Yosemite, with the ATI v1.6.6 kexts instead of the AMD v1.28.29 ones in the Extensions folder.

     

    To get these to load, I used Terminal to run this command, recommended by in this forum, in Terminal:

    sudo nvram boot-args=“kext-dev-mode=1”

     

    About This Mac shows the architectures of the ATI kexts provided via this forum as “i386, xm86_64”. So I took no specific steps before restarting to boot into 64-bit mode.

     

    My experience after updating to both Mavericks and Yosemite was similar to some other contributors to this thread. I had a bit of a fingers-crossed honeymoon period, but then random freezing and crashing started after about a fortnight. And once it had, the machine then became impossible to use for more than a few minutes.

     

    I now seem to have got it back. No thanks to Apple, of course, but to all the diligent work by the expert troubleshooters in this forum.

     

    The question is, if they can come up with a relatively simple solution, why can't the highly paid -- and increasingly smug -- geniuses at Cupertino?

  • by mattwinters78,

    mattwinters78 mattwinters78 Nov 11, 2014 12:08 AM in response to dmaude
    Level 1 (0 points)
    Nov 11, 2014 12:08 AM in response to dmaude

    dmaude

    If you read my post a few back there are 3 types kernel architecture utilized by Macs. But at the time in SN 10.6.2 when the working kext where written there where only 2 kernel architectures utilized in Macs(that I know of) i386 and x86-64. Straight 64 is different than x86-64 and taking no special steps to boot 64 happens because it is the default for 10.8, 10.9 & 10.10. At least for me in Mavericks telling my 7,1iMac(exact same as yours) to boot in x86-64 and not the 64 has resulted in zero freezes. I just haven't made the leap to 10.10. But since you have and are still having freezes running 10.10 with the terminal command:

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

    Try telling the kernel to boot in x86-64 not 64 with the command:

    sudo systemsetup -setkernelbootarchitecture x86_64

    Please post back if has worked or if you have found another solution.


  • by dmaude,

    dmaude dmaude Nov 11, 2014 2:46 AM in response to mattwinters78
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    Nov 11, 2014 2:46 AM in response to mattwinters78

    I expressed myself badly. The sentence "I now seem to have got it back" was intended to indicate that, thanks to your detailed instructions and the helpful contributions of others, I've had no freezes since persuading Yosemite to load the old kexts. But I'll keep your kernel boot mode instruction in reserve, just in case. Thanks again, to all, for a machine that works for me - and doesn't provoke desperate calls from my wife, whenever she tries to use it, of "aargh, it's done it again!"

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