Resolved MP 4,1 to 5,1 + W3690 + GTX750ti - won't boot after OSX 10.10.5 update

Discussion in 'Mac Pro' started by ithinkitsnice, Aug 26, 2015.

  1. ithinkitsnice, Aug 26, 2015
    Last edited: Aug 26, 2015

    ithinkitsnice macrumors member

    May 27, 2010
    I just restarted my system to apply the latest update to OSX (presumably to the current 10.10.5, I think I was on 10.10.3).

    As the machine reboots I hear the chime, see the grey apple logo as expected (stock video card connected to check progress) with progress bar, which gets to about halfway, then a multilingual error message appears for a split second (no time to read it), the screen goes black and the whole cycle repeats ad infinitum. Something's obviously not right.
    • I powered cycled with a PRAM reset and the only difference this made was the error message didn't appear anymore, otherwise the boot fails in the same fashion.
    • I tried [cmd-r] to boot into recovery partition, that had no effect (failed boot cycle as before).
    • I tried [opt] booting to check the recovery partition was actually there (which it was, showing a 10.10.3 recovery volume). However, selecting this results in the exact same cycle as before.
    • I tried [shift] booting into safe mode, that had no effect.
    I'm now downloading Yosemite from the app store on my laptop to try to make an external recovery volume, which I hope works.

    My question is this:

    Could any of the unsupported upgrades (5,1 flash, CPU, GPU) be causing this in some way? Everything was working perfectly before.

    Mac Pro 4,1 to 5,1 (single CPU)
    GTX 750ti (normally use Nvidia Drivers, but PRAM reset presumably wipes that out)
  2. h9826790 macrumors G5


    Apr 3, 2014
    Hong Kong
    The 1st thing I will try is remove the 750Ti. CPU is not a problem, my machine also apply the 5,1 flash with W3690 and 10.10.5, so that's not the root cause.
  3. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    1. Boot your Mac Pro with the stock video card.
    2. Install the Nvidia web drivers and enable them.
    3. Shut down.
    4. Install your GTX750Ti.
    5. Boot up.
  4. ithinkitsnice thread starter macrumors member

    May 27, 2010
    It was indeed the 750ti.

    Followed @pastrychef's instructions and I'm back in business (to be clear, I had to physically remove the 750ti before it would boot), so thanks very much for that.

    What's the procedure so I can avoid this next time? Should I have…
    • disabled the web drivers before update? (I assumed they'd get disabled by the update, failing that the PRAM reset would work)
    • updated the web drivers before update? (I assume they're 10.10.5 specific though)
    • removed the 750ti completely before update?
  5. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    The software update broke the previous version of the Nvidia web drivers. This caused it to default back to the built in drivers. When you try to a boot a Mac Pro with a Maxwell video card, it will crash the built in drivers and cause it go in to a boot loop.

    There are several ways to prevent this boot loop:

    1. The least technical way would be to remove the GTX750Ti prior to updating and reinstall after updating and installing (and enabling) the Nvidia web drivers.
    2. Another way would be to disable the built in drivers. Instructions a found in this thread, #24.
    3. In this thread, Troy2000 has instructions on how to modify your USB flash drive to include the needed Terminal command so that you can perform an update/upgrade. This modified USB flash drive can also be used to boot into and disable the built-in drivers.
  6. ithinkitsnice thread starter macrumors member

    May 27, 2010
    ok, that all makes sense. Don't know how I missed that #24 in the EFI thread, think I assumed #2 covered updates.

    Thanks again.
  7. mugwump macrumors regular

    Jan 10, 2004
    I have this same setup, and I usually share screen into the Mac Pro to do the OS/nvidia updates.

    My Dell 4K monitor is having issues waking up from display sleep, often causing a restart, but that's another issue.
  8. ithinkitsnice thread starter macrumors member

    May 27, 2010
    I'm about to make the leap to 10.11, just making sure I get this right.

    I worked out how to check at my boot args via terminal (nvram -p) and noticed I have…

    boot-args nvda_drv=1

    …which I'm guessing is the flag to load the web drivers.

    So, my questions are:
    1. Do I need to set boot-args="nvda_drv=0" as well as adding boot-args="nv_disable=1", or does the latter make that redundant?
    2. Once I've updated, is "boot-args="nv_disable=0" sufficient to disable it, or do I need to reset the boot args?
  9. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    You don't need any of these.

    Just plug in your original video card. Upgrade to El Capitan. Install and enable the Nvidia web drivers. Plug your GTX 750 Ti back in. Done.
  10. ithinkitsnice thread starter macrumors member

    May 27, 2010

    I know I can do that, but I am trying to avoid that because it's a bit of a mission with my physical setup.

    I was trying to follow suggestion 2 in your previous reply. Would that not work?
  11. pastrychef macrumors 601


    Sep 15, 2006
    New York City, NY
    The El Capitan upgrade is a bit different from previous upgrades. Towards the end of the upgrade, we are asked some questions and we must interact with the computer before the installation process is complete. I would recommend using your old video card for this upgrade.

    There's a good possibility that by the time the installer reaches this point, OS X is pretty much fully loaded and screen sharing is already active which would allow you to connect from another computer to complete those questions.

    If you still wish to attempt doing it this way, here's what you need to do:

    1. Enable screen sharing on the computer that you will be upgrading to El Capitan.
    2. Make sure you can connect to this computer from another computer.
    3. Launch Terminal and enter:
    sudo nvram boot-args="nv_disable=1"
    4. Launch App Store and begin the El Capitan upgrade.
    5. Sit back and wait. (I believe it took about 2 hours for my upgrade to finish.)
    6. At random intervals, try connecting to your Mac Pro from another computer using screen sharing.
    7. When you can finally connect, you should be able to complete the installation and then install and activate the Nvidia web drivers.
  12. ithinkitsnice thread starter macrumors member

    May 27, 2010
    Ok, thanks for that. Sounds like as much if not more hassle then. I'll just do the card switch.


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12 August 26, 2015