iMac 21.5" MID 2011 startup artifact

Discussion in 'iMac' started by idome, Sep 24, 2016.

  1. idome, Sep 24, 2016
    Last edited: Sep 24, 2016

    idome macrumors newbie

    Joined:
    Sep 24, 2016
    #1
    Hi, i´m quite new mac user. I noticed horizontal artifact on my mid 2011 (HD6770) 21.5" iMac screen on startup. I uploaded video:



    The artifact shows up at 0:29 on video. Also screen goes off and on, this is also new behavior after NVRAM reset. Is this normal? iMac works nice, no artifacts on normal use. Only couple seconds on startup, everytime. Problem started after I upgraded to Macos sierra and cleared NVRAM.
     
  2. kiwipeso1 Suspended

    kiwipeso1

    Joined:
    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #2
    You've found the driver problem with upgrading to a new system without wiping the old system first.

    To resolve it, first use time machine to backup your iMac system.
    Then create a macOS Sierra installer USB disk, from the instructions here :
    http://www.macworld.com/article/309...-a-bootable-macos-sierra-installer-drive.html

    Then restart, and hold option key. Select the installer disc to start the installation.
    Use disc utility to wipe the system drive clean.
    Then do a fresh install.
    Wait until it has booted, then restore from time machine your apps and settings.

    This is the only reliable way of fixing the problem with 2011 iMacs and video driver issues. Have done it a couple of years ago with eventual success once I did it this way.
     
  3. idome thread starter macrumors newbie

    Joined:
    Sep 24, 2016
    #3
    Thanks, but I made clean install from recovery menu after sierra upgrade. Wiped the system drive and installed sierra again. (I think USB-stick method or recovery menu install is the same, or does it make difference?) Problem still occurs. If I remember right, the problem started after NVRAM reset.
     
  4. kiwipeso1 Suspended

    kiwipeso1

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    Wellington, New Zealand
    #4
    Install USB method is different, as it can fully wipe drive. Recovery menu only does partial overwrite wipe.
    Recovery Menu is only useful for corrupted system, but install USB is considered 100% reliable.
     
  5. idome, Sep 24, 2016
    Last edited: Sep 24, 2016

    idome thread starter macrumors newbie

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    Sep 24, 2016
    #5
    I have recovery partition, so last time i fully wiped my primary partition. So, doing that way are there really any difference between USB and recovery install?
     
  6. Fishrrman macrumors G4

    Fishrrman

    Joined:
    Feb 20, 2009
    #6
    I've seen "video glitches" during startups as well (on various Macs using various iterations of the OS).

    You might be able to clean this up with a re-install of the OS, but…

    … so long as it runs as it should after bootup is completed, without any other video-related problems, I'd just let it go for now...
     
  7. kiwipeso1 Suspended

    kiwipeso1

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    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #7
    @Fishrrman It's a specific fault with video drivers for mid 2011 iMacs on previous OS X versions not being updated when you upgrade the system.
    Having had this fault on my mid 2011 iMac 27" when going from Mavericks to Yosemite, it is entirely likely that this would persist with worse effects unless the system is clean installed, as I had to do a couple of year ago.
     
  8. PH11235 macrumors newbie

    Joined:
    Mar 5, 2017
    #8
    I have the exact same artifact, almost pixel for pixel, showing up on my mid-2011 27" iMac with HD 6970 GPU at the same point during startup. I assume this is right around when the computer is switching control of graphics processing over to the GPU. To anyone that knows better than I do, is that assumption accurate?

    Anyway, my card crapped out a couple weeks ago and was keeping my computer from fully booting in any mode. Thinking back, the artifact showed up while I was trying everyone's typical troubleshooting solutions... i.e. NVRAM reset, SMC reset, etc. At the time I assumed it was just another symptom of my card failing, but I'm wondering now if it was actually the NVRAM reset like you were saying.

    Ultimately, I ended up having to pull my graphics card and send it out for repair, and my computer seems to be functioning 100% normally right now aside from the artifact at startup. I've tried erasing my SSD and reinstalling osSierra as others suggested but no luck on preventing the artifact. I'm wondering, have you had any other issues since you posted, has it turned out to be just a minor annoyance when turning on the computer, or were you ever able to find a way to fix it?

    Also, to anyone, and for what it's worth, the artifact only shows up when booting normally from my SSD. If I boot in safe mode, diagnostic mode, recovery mode, or from a bootable USB, there is no artifact. I'm almost tempted to install a copy of osSierra on my HDD so I can boot from that and see if there is still an artifact. Would that be a worthwhile troubleshooting step, or not worth the effort?
     
  9. dfine1966 macrumors 6502

    Joined:
    Apr 9, 2011
    #9
    I had the same problem with my mid-2011 27 inch iMac 3.4 Intel Cori i7, 16 GB Memory, AMD Radeon HD 6970M 20148 mb. At first I couldn't figure out the problem. Three years ago I had the other problem with video card and motherboard that was replaced by Apple under warranty.

    To get right to the point, the problem was caused by MacOS Sierra and also using PRAM reset holding P and R and command option.

    This is how I fixed it, but you can't do the PRAM reset again or it will come back

    First thing you need to do is download el Capitan and install it on an external hard drive. Once installed, boot it up through your mac and reboot a couple of times. After that, switch back over to your normal drive that you have Sierra installed and the glitch will be gone. It will actually run smoother than before. If it happens again, just run the external boot up of the el Capitan and it should be gone again.
    If you use the PRAM reset again that video glitch will return and you will have to run that external drive again.

    Give it a try.
     
  10. ElCani macrumors member

    Joined:
    Jun 15, 2012
    #10
    I've had the exact same thing for a while (prob since Sierra) on my 2011 iMac 27. I just ignore it. :)
     
  11. PH11235 macrumors newbie

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    Mar 5, 2017
    #11
    I created a 16 GB partition my internal HDD and reinstalled OS X El Capitan on it. Looks like it's remedied the artifacting going on. Thanks for the advice on the fix...
     
  12. kiwipeso1 Suspended

    kiwipeso1

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    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #12
    As I've said on other threads, the problem is likely to be with the video driver not updating with the new OS upgrade.
    The easiest way to solve it is to back up your iMac with time machine, then install from an USB disk (which you then wipe your internal drive first, then clean install Sierra), you then restore selectively from time machine your user accounts and applications.
    Bingo, problem solved. (I've done this with mavericks upgrade from mountain lion, with the same issue).
     
  13. dfine1966 macrumors 6502

    Joined:
    Apr 9, 2011
    #13
    Actually, I did what you suggested first. I did a clean install using a USB drive of Sierra. It didn't work. MacOS Sierra is the problem. What I suggested is the only way right now to fix it. The one thing I noticed was that it seems to be confined mostly with 2011 Mac's with MacOS Sierra.
     
  14. kiwipeso1 Suspended

    kiwipeso1

    Joined:
    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #14
    It would seem that the problem only remains if you do a PRAM reset. In which case, it is no longer necessary for macs of that vintage.
    I am sure that if you call Apple, they will blame you for doing something no longer necessary on modern macs.
    Sorry, I can't help you.
     
  15. nambuccaheadsau macrumors 6502a

    nambuccaheadsau

    Joined:
    Oct 19, 2007
    Location:
    Nambucca Heads Australia
    #15
    Used Sierra on my 27" 2011, late 2013 and 2016 iMacs and have never noticed it.

    That 38 seconds sure seems a pretty slow boot process for an SSD.
     
  16. kiwipeso1 Suspended

    kiwipeso1

    Joined:
    Sep 17, 2001
    Location:
    Wellington, New Zealand
    #16
    It usually takes 5 ~ 8 seconds on my Samsung 840 SSD to reach login depending on restart or startup from cold.
    Perhaps it's a SSHD ? Or a really cheap SSD ?
     
  17. Lankyman macrumors 68000

    Joined:
    May 14, 2011
    Location:
    U.K.
    #17
    My mid-2011 21.5" iMac has exactly the same issue as yours. Thank goodness, I thought it was just mine and might have been indicative of some impending failure phew!. :(
     

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