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  1. #1
    Can't reinstall MacOS on 2011 iMac
    Hi,

    I've got a 2011 iMac that I can't seem to re-install any version of MacOS on. I've tried installing both Majove (10.13) and High Sierra (10.12) from a USB drive and the problem is either that it gets stuck in a reboot loop, or I see the non-bootable disk icon when trying to boot from the USB drive.

    I even have original install DVD for Snow Leopard (10.6) which I've tried but I get the following linux screen:

    IMG_9968.jpg

    Not sure if that gives any clues as to a possible hardware problem or whether it's simply that Snow Leopard won't run on a 2011 iMac.

    A bit of further background: I used to have two external displays connected to the iMac and during a recent MacOS update I foolishly decided to disconnect one of the displays. This caused the Mac to crash and get stuck in a reboot loop which I finally got around (can't remember exactly how). But since then the Mac will only boot if one of the external displays is connected. If I tried to boot without a display connected it would simply get stuck in a loop.

    Currently the Mac isn't bootable at all.

    Admittedly it's been a while since I've attempted to resurrect the Mac again but does anyone have any suggestions for what I could try or what might be the problem? The main goal is just to re-install a working version of MacOS again.

    Thanks.

  2. #2
    Can't reinstall MacOS on 2011 iMac
    dtravis7's Avatar
    Member Since
    Jan 04, 2005
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    iMac late 2012 21.5 i5 10:14. iMac 2010 27"QuadI7 OS10.13, MBPLate2011, iPad Pro10.5", iPhone7
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    First, Mojave will not install on a 2011 Mac at all. Has to be a late 2012 with the glued in screen.

    For your monitor and booting issue try resetting the PRAM. Also the PMU.

    How, When, & Why to reset the PRAM & SMC on your Mac

  3. #3
    Can't reinstall MacOS on 2011 iMac
    ferrarr's Avatar
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    You can also attempt Safe Mode boot, Use safe mode to isolate issues with your Mac - Apple Support.

    Edit: I would also try, both what Dennis said above and my suggestion without any external devices connected to the iMac.
    Last edited by ferrarr; 04-13-2019 at 08:27 AM. Reason: Added info
    -- Bob --
    Please backup. Everything has a life cycle, unexpected and warning free. Nothing will last as long as you want it to.

  4. #4
    Thanks, that's useful to know about Mojave.

    Thanks also for the suggestion about the PRAM and SMC - I think I'd tried PRAM but not SMC. I've just done them both, twice, and still no luck.

    I'm trying the Yosemite installer on a USB drive now and I get the grey installer screen with the Apple logo and progress bar. It runs for about 15 minutes and gets about half way and then the machine restarts and begins the whole process again. I've left it in that loop for about 5 goes now.

    I've got a USB keyboard plugged in and USB flash drive and that's it - no additional devices.

    The Mac itself has an SSD.

    Any other ideas what could possibly be up? Could it be a hardware issue?

    Thanks.

  5. #5
    Quote Originally Posted by ferrarr View Post
    You can also attempt Safe Mode boot, Use safe mode to isolate issues with your Mac - Apple Support.

    Edit: I would also try, both what Dennis said above and my suggestion without any external devices connected to the iMac.
    Thanks - no luck with safe mode - I just get the non-bootable drive icon (circle with a diagonal line though it).

    The Mac was running ok before I tried to reinstall the OS (apart form the issue with it only booting with an external display attached), so it's clearly not complete hardware failure.

  6. #6
    Can't reinstall MacOS on 2011 iMac
    chscag's Avatar
    Member Since
    Jan 23, 2008
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    Keller, Texas
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    2017 27" iMac, 10.5" iPad Pro, iPhone 7+, iPhone 8, Numerous iPods, Mojave
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    I'm trying the Yosemite installer on a USB drive now and I get the grey installer screen with the Apple logo and progress bar. It runs for about 15 minutes and gets about half way and then the machine restarts and begins the whole process again. I've left it in that loop for about 5 goes now.
    It could be that your internal SSD in that iMac is the problem. That Yosemite installer USB drive if it is in fact a good installer should have been able to boot the machine and run the install.

    I would try booting the iMac with a good known installation of macOS from an external hard drive. If the machine boots and runs macOS from the external hard drive, you can bet the SSD is the problem. If the machine won't run from an external bootable hard drive, then, you have other serious problems. Possibly a bad GPU.

  7. #7
    Can't reinstall MacOS on 2011 iMac
    dtravis7's Avatar
    Member Since
    Jan 04, 2005
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    iMac late 2012 21.5 i5 10:14. iMac 2010 27"QuadI7 OS10.13, MBPLate2011, iPad Pro10.5", iPhone7
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    Agree with Charley. If the Internal drive is messed up in a bad way I have seen installer booting issues.

    Try what Charles suggested and try and boot from an external with the OS on it. Is this your only Mac?

    If down the road you find it to be a GPU issue, That model I am quite sure has a Plug in Video card. You sure that is a 2011? What size is the screen? 21 or 27"?

  8. #8
    Can't reinstall MacOS on 2011 iMac
    chscag's Avatar
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    It's showing up as an iMac 12,2 so it must be a Mid 2011 27" iMac. I believe that model did have a plug in video card.

  9. #9
    Can't reinstall MacOS on 2011 iMac
    pm-r's Avatar
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    Quote Originally Posted by chscag View Post
    It's showing up as an iMac 12,2 so it must be a Mid 2011 27" iMac. I believe that model did have a plug in video card.

    Yikes, that's the same as my 27" 27GHx iMac and yes, they came with a replacable AMD Radeon HD 6770M graphics card, but gheese, some crazy prices for replacements at some places these days if that is what has gone kaput.

    PS: If replacement is mandated, I believe the later AMD Radeon HD 6970M (I believe is correct) graphics will work and can also support more memory. They are also the same model cards that Apple provided an extended warranty replacement on.



    - Patrick
    ======

  10. #10
    iMac won't function without an external display connected
    Hi all,

    I have a mid 2011 27" iMac that has a strange problem: it will only boot successfully if an external display is connected via a Thunderbolt port. If I disconnect the external display and try to boot I see the Apple logo with the progress bar underneath which gets about half way along and then the machine reboots. It will stay in this reboot cycle until I power off and connect the external display.

    I have just done a fresh install of Lion and then updated to Mavericks and then High Sierra which it's running now. I've tried a fresh install without the display connected but the installer keeps rebooting.

    I've reset PRAM/SMC multiple times to no avail.

    I've also tried booting into Safe Mode and the progress bar gets almost to the end before rebooting.

    I've checked the Console logs but I can't see anything in there at all as the reboot seems to happen before it starts logging.

    The strange thing is that the monitor doesn't even need to be powered on. I can disconnect the monitor power supply and just leave it connected to the Mac and it will boot happily. if I remove the HDMI/Thunderbolt cable from either the monitor or the Mac then it fails to boot.

    As some background, the problem did seem to start when I foolishly disconnected one of the two external displays whilst some updates were installing. This caused the Mac to reboot and ever since then it will only boot with a monitor connected.

    Can anyone think of any way of diagnosing the problem? I haven't yet tried with a different external display, but I can do so. Is it worth trying EtreCheck or similar?

    I am trying to prepare the iMac for sale but fear I will need to sell it along with the additional monitor and of course make the buyer aware of the issues.

    Thanks all.

  11. #11
    Thanks everyone for the responses.

    It is indeed a mid 2011 27" iMac.

    I've managed to do a fresh install of Lion by booting from a Time Machine drive and using the option if gave me there. It was only possible to do this whilst the external display was connected. I've since updated to Mavericks and now High Sierra.

    The problem with the external display persists. I cannot boot the machine, or do a fresh OS install, without the display connected. I've reset PRAM/SMC multiple times and tried booting into safe mode.
    Last edited by chscag; 04-15-2019 at 05:25 PM. Reason: Threads were combined. Link to new thread removed.

  12. #12
    I would try booting up (with the external display connected of course) and hen taking a look at System Preferences > Displays to see if there is anything there to "unlink" thee xternal display.
    I don't use High Sierra, but I think it's possible that the Mac is somehow looking for the "connected" display during boot up and stops booting when it doesn't find one.
    By "connected" in quotation marks - it's connected in software.

    I assume when you boot up with the external displzyconnected, the iMac main display comes up fine.

  13. #13
    Can't reinstall MacOS on 2011 iMac
    pigoo3's Avatar
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    Quote Originally Posted by glastoveteran View Post
    I am trying to prepare the iMac for sale but fear I will need to sell it along with the additional monitor and of course make the buyer aware of the issues.
    I would really think that this issue is more of something software or OS related...and not hardware (since I'm assuming the builtin iMac display works when the external monitor is connected).

    If you're prepping the iMac for sale...I would totally wipe/reformat the internal storage completely...then do a fresh virgin install of the OS. This way you can 100% confirm if there's a hardware/software issue...and if it's a software issue...100% eliminate anything that may have accumulated on the internal storage from years of use.

    Before doing this...make sure you have a bootable installer of at least one version of the OS...or you can use the Recovery Partition or Internet Recovery to do the fresh install.

    HTH,

    - Nick
    - Too many "beachballs", read this: Beachballs
    - Computer seems slower than it used to? Read this for some slow computer tips: Speedup
    - Almost full hard drive? Some solutions. Out of Space
    - Apple Battery Info. Battery

  14. #14
    Can't reinstall MacOS on 2011 iMac
    ferrarr's Avatar
    Member Since
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    Have you tried the Apple Hardware test, How to use Apple Hardware Test on your Mac - Apple Support
    -- Bob --
    Please backup. Everything has a life cycle, unexpected and warning free. Nothing will last as long as you want it to.

  15. #15
    Can't reinstall MacOS on 2011 iMac
    chscag's Avatar
    Member Since
    Jan 23, 2008
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    Keller, Texas
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    Both threads have been combined.

    Please do not start a new thread when the subject matter is the same or leads on as the same.

    Thanks.

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