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  • apple_power Level 1 (55 points)


    my MacBookPro Early 2011 shows the exact same problems, is there also a replacement



    Here the data from my Macy-Baby:

    MacBookPro 8.2 (15-inch, Early 2011)

    Processor  2.2 GHz Intel Core i7

    Intel HD Graphics 3000

    AMD Radeon HD 6750M 1024 MB


    As long as I force it to use the Intel HD Graphics 3000, it works fine.

    As soon as I start using Aperture with the AMD Radeon HD 6750M or even when I plug in the Thunderbolt-Display, the screen shows after 2 or 3 minutes some artefacts and starts flickering. Sometimes it ends up in a blue and black striped screen… and FREEZES




    It all started about a year ago with an other symptom, whenever I woke up the computer while Aperture was running, only the internal display came up but the Thunder-Bolt display stayed dark. Turning off and on the Thunder-Bolt display or unplug/replug it solved the issue.


    I know, this is the iMac Discussion, but since the problem is the same (and the hardware is similar), I try to post it first here.
    and enjoy your Apple
  • MrBelloNLD Level 1 (0 points)

    just to let u know:

    27-inch, medio 2011, with AMD Radeon HD 6970M - 1024


    bad GPU (distorted blue screen with vertical lines while booting recovery mode from Mavericks, normal boot gray apple logo, after that white screen (staying white))

    gpu replaced under warrenty by Apple's "hidden" repair program:


    info from old and new system-profile:

    OLD GPU:ROM-revision:113-C2960H-188
      Version EFI-besturingsbestand:01.00.544
    NEW GPU:ROM-revision:113-C2960H-203
    Version EFI-besturingsbestand:01.00.560


    maybe helps other with same sort of problems, kind regards

  • hamah Level 1 (0 points)

    Sorry to see this thread continuing over 133 pages in length and through so many OS X updates. Also sorry to note that I am also experiancing video artifacts that appear as flickering "checkerboard" or "pixelated blocks" similar to what reich360 posted (I've grabbed his image and inserted it below).


    I too have a 27" mid-2010 iMac. I too have seen these problems appear since Lion. They have gotten progressively worse over time and I honestly can't, at this time, directly blame a failed/failing GPU (ATI Radeon HD 5750), a piece of 3rd party software, or the OS itself (such as drivers, pref settings etc.)


    Here is what I can say to date.

    -the video artifacts problem never, or very rarely, resulted in screen freeze, kernel panic etc. until Mavericks. It will now freeze/lock up after anywhere from minutes to 3 days after a PRC reset.

    -I have tried to isolate to the iMAC by unplugging all external devices but bluetooth keyboard and mouse to no effect

    -I have tried isolating to DRAM with no effect. It happens with any or all my DIMMs in place (4x4GB)

    -when the screen freezes the cursor will either have it's normal shape (arrow pointer) or more typically the beach ball. Eventually (it takes 30 minutes or so) the cursor also freezes and after a further period of time the screen will dim. On occasion the system will reboot on it's own but often it will require a hard power reset.


    This is an interesting observation:

    -while the screen is frozen the iMac will not accept a VNC connection and an existing one will fail BUT you can still ssh into the iMAC. You can ping, look at error messages tailed to the terminal etc, (does anyone have any idea what useful info I should gather at this point?).

    -I will then do a remote shutdown from the ssh session (sudo shutdown -r now) at which point the ssh session is terminated BUT the iMac NEVER completes restart and sits there hung. A hard power reset is always required and sometimes I will end up with a crash report (kernal panic) but often it will be a silent failure (or at least I don't know enough about where to look in the logs for more detail)


    At this point I have done a fresh install of Mavericks, have left all peripherals (but keyboard and mouse) disconnected and have only modified a few settings (mostly account based sharing and connectivity related to allow for ssh logins etc). Already I have seen some of the blocky video artifacts after 1:10 of system uptime. I'll update when/if the system hangs or crashes.


    My next action will be to either add boot camp and Windoze so that I can edit the GPU bios per Andrew Humphreys' post on page 120 of this thread or I will simply take the iMac into Apple for a GPU replacement.



    sample problem.jpg

  • Carlos Madrigal-Sánchez Level 1 (0 points)

    It will be a total success if GPU overclocking work for you but even Andrew said that it wasn't working for him within Mountain Lion latest updates.


    Check if you just need to set the parameters to the default levels. I changed a misconfigured voltage from .9 to .95 and that made the trick (Note that I was having freezes only, no artifacts)


    GPU replacement has worked with all the guys having those artifacts so it's a straightforward solution.


    Good luck!

  • hamah Level 1 (0 points)

    My preferred thing will be to replace the GPU depending on cost. I'm not a big fan of overclocking. So far though I seem to be stable on a fresh install (although I have already seen some minor artifacts as I mention above). All my peripherals are reatttached and I'll slowly start to add apps and configure as required over the coming days while taking lots of notes (and with fingers crossed).


    Another interesting observation that I'll be looking to replicate is that when I started to see the artifacts after the fresh install I closed apps until I got to Finder. A relaunch there stopped the artifacts cold and I've repeated that twice since.


    I'm keeping an ssh session open from my MBP and if I see a screen freeze/lock up I'll be trying trying 'killall Finder' to see if it is possible to unfreeze the screen remotely.


    This could very well be just a flaky GPU but at $500+ to replace I'm hoping to pin this on Apple


    BTW What are the default settings supposed to be? If (when) I see the screen freezing again I'll likely try the overclocking method just for fun and experiance but it would be interesting to check to see the clock and voltages are correct before doing so.

  • Carlos Madrigal-Sánchez Level 1 (0 points)

    These are the ones that I think are the default params because they are shared between users of this forum that have published them (around page 30)


    1: 628 1000 1V

    2: 157 295 .95V

    3: 503 1000 .95V

    4: 398 1000 .95V


    These were my original params (when it freezed)


    1: 628 1000 1V

    2: 157 295 .9V

    3: 503 1000 .9V

    4: 398 1000 .9V


    You just have to change that 2nd one to .95 and 3 and 4 will change automatically to .95 too.


    If you follow Andrew's guide this values will make sense when you have to put them.

  • hamah Level 1 (0 points)

    Well this morning the screen was frozen with all the same symptoms as before. This was about 9 hours after installing Drobo Dashboard and restarting the system and plugging back in all my external drives and printer. I had noticed some IOUSBFamily errors in Console and had an issue where plugging in a drive cuased a "failed to enumerate" error but when I re-plugged that drive all was ok. This led me to wonder if I have have a logic board issue and/or a GPU issue.


    Using ssh I unmounted all the drives and attempted a 'halt' which, as with the 'shutdown' command, never completed and I ended up shuting down the power to restart.


    I now notice that the console is full of kernel entries 'GPU Hang State = 0x00000000', 'GPU hang', 'Trying Restart GPU ...' so it does seem the GPU is likey fubar. For fun I will try to edit the bios but I have no faith that will do anything.


    Without reading pages 1-119 has there been any success in getting Apple to recognize a high failure rate of the ATI Radeon HD 5750 and replace it out of warrenty?

  • Thetis Level 1 (65 points)

    I had this problem, which kept recurring over about 6 months. I kept taking it back in to the Apple store for them to diagnose and replace things. (Which they somehow were doing free despite me being out of warranty)


    By my third visit, everything but the motherboard had already been replaced at least once. They kept my iMac for about a week, and finally just decided to replace it for me.


    So my local Apple store, after several visits with the dang thing, did finally just take it and give me a new 27" iMac.


    Keep documenting your problems, and each time it keeps happening take it back in for them to diagnose it. They may eventually, finally, agree that it's a lemon and replace it.


    Don't give up.

  • Gandalf The Grey Level 2 (275 points)



    They gave me a instore credit for my unit, then I used a Mac Mini for almost 2 years and then finally bought the newer much cooler iMac in June of 2013, one thing I noticed right away if you touch the newer units they run cool, even the ones at BB and the Apple Store that been on all day. I was told by Apple under warr, after 3 repairs you can get a in-store credit or a new machine, at the time in June 2011, I wasn't going to get a new one at the time because I thought they were having heat issues in all of there units.

  • mpick92 Level 1 (0 points)

    I had the same exact symptoms as Andrew Humphreys (page 120) with my mid-2010 iMac with ATI 5750.

    Screen Shot 2013-12-24 at 10.22.13 PM copy.jpg


    Background note:

    I had artifacts on my iMac running 10.8.x (sometimes in Windows partition) and thought I could fix this with a fresh install of Mavericks 10.9.1. However, right away the fragments came back. Of course I didn’t purchase AppleCare (which would have been out of date anyway, hard to believe I’ve had it 3 years already), so I went out to the inter-webs to find a fix, and came upon this thread.


    Thinks Andrew Humphreys, here is a simplification of what I did:


    Main steps:


    1. Boot into your windows partition (the only way to flash the graphics card)

    2. Save your current BIOS rom using GPU-Z download option


    3. Edit the BIOS .rom file to your specifications with RBE (Radeon bios editor)


    3a. My settings were 157 (GPU) and 295 (RAM) to 398 (GPU) and 1000 (RAM)

    note: there are different settings for different idle states (there will be one state that is lower than the rest with the settings of 157 (GPU) and 295 (RAM) )


    4. Flash the BIOS using ATI winflash

    5. Reboot and check with GPU-Z that your settings flashed correctly

    6. Boot into OSX and see if the fragments are gone!

  • Ninklesko Level 1 (0 points)

    Hello Everyone,


    I have recently had this issue and noticed some additional issues with the graphics fairly recently with my 2010 iMac as well.  I have not read through all 133 pages but have seen enough to realize the commonality of the issue.  If anyone is digging through this and would like to reference other threads, I linked what I have currently come across (down below).


    In addition to the flickering squares I have seen the following:

    Rotation of in game text (basically 2D text that rotates around 360 degrees, cuts off, very odd behavior.

    Skins/textures of in game characters flickering black/white/green.

    Pretty much a seisure of colors (more dominantly green) in Minecraft but flickering green/pink/white/black.


    Additional Discussions

  • steinmanal Level 1 (0 points)



    Thanks for the post. After completing the steps in your post, have you had any more issues with the video / freezes?


    I've got a 27" 2010 iMac with the Radeon 5750 with the same issues. I'm looking for a recall or some solution.


    Thanks much.



  • mpick92 Level 1 (0 points)



    The system has been completely stable, but unfortunately the fragments have started to come back...


    The computer doesn't freeze up which is nice, but there are still some lingering fragments when I scroll on webpages, etc.


    I might drag my iMac to the apple store and see what they think (I'll have to reflash the graphics card to original settings).


    For me, the bios flash has been a nice band-aid, but will eventually need to fix the graphics card.


    Picture below is after the bios flash (less intense fragments, but fragments nontheless).

    The system has not completely frozen on me, so the "less intense" fragments are just a nusance. Hopefully it doesn't get worse.


    Screen Shot 2014-01-14 at 12.19.46 PM copy.jpg

  • Carl Ketterling Level 1 (15 points)

    I want to share that I, too, had the problem with graphic artifacts/glitches appearing.  The problem got so bad that the machine was mostly unusable.  I followed the instructions from Andrew Humphreys on page 120 (many thanks to Andrew for such a well-written post).  My machine became usable again, but some of the graphic artifacts continued.


    The initial problem started just after the AppleCare expired, but I'll be taking it to an Apple store to get their opinion.


    For reference, I have this hardware: iMac "Core i5" 2.8 27-Inch (Mid-2010)

  • A. Richards Level 3 (625 points)

    I have a 2010 iMac, mine is a 27" 2.93 GHz i7 with the Radeon HD 5750 1GB GPU (ROM rev. 113-B9710C-238, EFI driver v. 01.00.417). I started seeing the artifacts like others here around the time I upgraded to Mavericks (now at 10.9.2).  As time went on, I started getting the video freeze save for the working mouse cursor.


    I tried Carlos Madrigal-Sánchez's GPU BIOS voltage tweak first, and things were clean for the rest of that day, but after a lengthly sleep the iMac awoke to a black screen with only a working mouse cursor, so I rebooted into Windows 7 again and added the clock changes Andrew Humphreys recommended on page 120 of this thread. It has been a few days since then, and I've seen one brief instance of the artifacts. Fullscreening an app to force the whole screen to refresh cleared it and it hasn't returned in another 36 hours.