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  1. #1


    Member Since
    Jan 04, 2017
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    Mac Pro, 2012, boot loop
    Hi all.

    I'm new to the forum so please be kind if I make a mistake

    I have a Mac Pro, 2012 I suspect, that is failing to boot. I've tried most of the weapons I have available but to no avail.

    The story so far:

    Put simply it fails to boot. I have two, original 3.5" HDD's available, both loaded with working operating systems, disk 1 is OSX 10.11.6 El-Capitan, disk 2 OSX 10.5.6 Leopard. At power up, with one or the other of the disks in place the machine starts to boot, a progress bar shows on the monitor, gets half way though and then crashes out, no error messages or feedback, just a hard reset. Left to its own devices the machine will boot loop, continuously crashing and rebooting half way through the load sequence. If I remove the drives completely and try boot to one of the numerous CD and DVD install images I have available I get exactly the same result. If I try cmd+opt+P+R I get the same result. If I try opt+D I get the same result. If put a new blank HDD in and a CD Snow Leopard and then tell the system to boot to CD then I see different behavior, I'm given the chance to install, but when I give the instruction to install I get the progress bar, half way through followed by a crash reboot. I've tried all the keyboard combinations I can find, same result, all the recovery options I can find, same result,

    I'm at my wits end. I suspect either the firmware or something along the lines of the disk controller is stuffed. If nothing else the error state is consistent in its behavior.

    Any suggestions you might have would be greatly appreciated.

    Regards

    A frustrate tech named Alan

  2. #2

    MacInWin's Avatar
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    2015 rMBP, 2008 iMac, iPhone 7, iPad mini, 13" MBP, AppleTV and two MacMinis
    It sounds like either a logic board problem, or maybe a memory issue. Given you can reboot from the CD, do that and then STOP at that point. Don't try to install. There should be a "Utilities" menu and the  logo in the upper left corner. Use the  to get to About This Mac and get the model information from there. Yes, I know you said maybe 2012, but get the actual version. Once you have that information, post back with that here. Then you can try reseating your memory chips and cards. You said it's a Mac Pro, which is a desktop, so you can try reseating the cards to see if any are not making good contact. Finally, reboot from the CD again and this time don't run the installer, just use Disk Utility to see if you can check the HD. The fact it can boot from the CD is encouraging, sort of pointing to something encountered later on in the boot process, like a memory chip failure or a drive problem in some other area of the disk(s).

  3. #3


    Member Since
    Jan 04, 2017
    Posts
    8
    In the interest of keep things up to date I've been able to track down a more acurate D.O.B for this Mac, it's a 2008 model.

    Regards

    Alan

  4. #4


    Member Since
    Jan 04, 2017
    Posts
    8
    Thanks for the reply Jake.

    I've tried several times unsuccessfully to get to utilities, but I'll follow your suggestions now and try again making notes as I go. I'll keep you posted.

    Alan

  5. #5

    MacInWin's Avatar
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    2015 rMBP, 2008 iMac, iPhone 7, iPad mini, 13" MBP, AppleTV and two MacMinis
    The CD boot SHOULD have Disk Utility on it, if for no other reason than to format a brand new drive to prep it for installation.

  6. #6


    Member Since
    Jan 04, 2017
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    I've reached the final straw with this device. I looked more closely at it yesterday and today. With install media in the ODD and three different working operating systems installed on three different functioning HDDs I can press opt key at boot get to a start up manager. I can clearly see all the drives and their respective recovery partitions . Regardless of the selected boot method I get the same results as before, half way through the progress bar and a hard reset. Even with the Ethernet connected, same result, if I do opt+d, same result. Whatever is preventing this device from booting its common to all possible boot option, this makes me think it's a hardware issue. I did think I could test the RAM but this device uses something called "FB RAM"!!!

    I draw the conclusion that either the MOBO or the FBRAM are in fail state but I have no way of testing against these so I've decided to call it.

    Thank you Jake for your suggestions.

  7. #7

    harryb2448's Avatar
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    Suggest replacing the PRAM battery, then removing two drives just leaving the El Capitan drive in Bay One. Try to boot and immediately hold down Command + R to see if you can get into Recovery Mode, and if any joy, into Disk Utility, bottom choice, and run Disk First Aid. Why are you running Leopard OS X.5? Tell us about your Snow Leopard DVD. Any chance it is a silver grey disc or is it the white disc with the cat on it? At the end of the day it is now nine years old, a pretty good run.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  8. #8


    Member Since
    Jan 04, 2017
    Posts
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    Thanks for the reply Harry

    I have to smile. I'll have yet another crack at fixing this piece of kit.

    The drive with Leopard on it is a legacy drive, removed from the machine when it was upgraded some time ago, it's been in storage since then as a just in case option, it was fully functional when removed so I've been playing with in an attempt to get this machine to respond differently.

    I've been inside and cleaned the heatsinks today, and replaced the CR2032 (2.99v/3.44v).

    With no media in the ODD and the El-Capitan 320GB HDD in slot 1 using cmd+r I see the same result, the Apple on the screen and a progress bar that gets half way before a hard reset. With Ethernet connected I tried cmd+opt+r and see the same again. Incidentally, if I attempt to boot to recovery it's 2 mins until the restart, if just let system attempt to boot from the HDD it fails after just 30 seconds

    The install media I've been attempting to work with are all copies, having said that they have all been used for various rebuilds installs and tests so know they're good.

  9. #9

    harryb2448's Avatar
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    Well Alan that is grim. Have you tried as a last resort replacing the graphics card? those models used either a nVidia 8800GT or an ATI Radeon 2600XT, both of which were pretty low performing and wih high failure rates.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  10. #10


    Member Since
    Jan 04, 2017
    Posts
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    It's grim indeed Harry.

    I'll try replacing the graphics card next week now, currently a Nvidia, I don't hold out much hope but I'll keep you posted.

  11. #11


    Member Since
    Jan 04, 2017
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    I have fantastic news. The graphics card solved the issue. I should have known better. I think as a tech that sometimes we get too close to the issue and simply can't see the wood for the trees.

    In the end I took the Apple resident Nvidia home to install in my own machine. Windows 7 booted to the card; post had artefacts that I chalked up to loose cables or connectors. I arrived at a 800x600 desktop (no artefacts visible), Windows complained a little but installed the new driver and requested a reboot. On reboot the progress bar appeared, then disappeared and left me with a blank screen covered green and red flecks, it waited a minute or so before a hard reset, then the whole sequence repeated.

    I had to really dig around to find a compatible graphics card for the Mac Pro but my 5th attempt was the charm. I noted that the first of the cards I tried (very old and low spec) did not cause the boot loop but I had no display. The 5th card did the trick, a blank screen to start but after 2 couple of minutes, to my delight, up it came.

    I can't thank you guys enough for your help, I was at points during this trouble shoot ready to throw the damn thing out of the window, but hey, its solved.

    Thanks again

    Alan, a very satisfied and pleased tech.

  12. #12

    harryb2448's Avatar
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    Good work. What card did you finally go with - an ATI RADEON 5700 series card?

    Very pleased to have been of some little assistance.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  13. #13


    Member Since
    Jan 04, 2017
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    I used a Nvidia GeForce 9500GS, just to prove the fault, it turned out to be the only card I had available at the time that was compatible. I'll order a new card over the coming week or so, I'll probably end up with a copy of the original just to make life simpler.

    Thanks again Harry and MacInWin, top blokes you are

  14. #14

    MacInWin's Avatar
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    Give Harry his props for the suggestion by ciicking on the thumbs up symbol on his post, the one on the far left below his screen name and information.

  15. #15

    harryb2448's Avatar
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    Thanks Alan and Jake!
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

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