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Struggling to downgrade from Mountain Lion to Snow Leopard

Hello,


I'm attempting to downgrade a Mac Pro from Mountain Lion to Snow Leopard as Mountain isn't compatible with some of the software on the machine. The machine was sent in for repair as it kept crashing when trying to render in After Effects. The machine came back after being completely wiped with Mountain Lion (an upgrade from the original Snow Leopard) and with a new internal hard drive that seems to have created two partitions.


My colleague has since wiped the computer again to try and reinstall Snow Leopard and apart from being unable to boot from the Snow Leopard installation disk there seems to be no other problems or error messages. I have tried holding Alt when starting up and it doesn't show anything other than a recovery drive. I've tried holding C and the computer freezes on the starting Apple icon so I'm unable to boot straight from the disk.


I've also tried to copy the installer onto an external hard drive but again, it isn't recognised when hitting any relevant keys during start up. However, both the disk and drive are recognised once in Utilities. I can't go back to Mountain Lion as a temporary fix as I receive an error message saying that it's unavailable. The computer is stuck in limbo and I'm desperately unsure of what to do next. Any assistance would be very appreciated.


My rough estimate of the specs is below (they're aren't exact I'm afraid).



Mac Pro "Twelve Core" 2.66 (2010/Westmere)2.66 GHz 6 Core Xeon X5650 x2
User uploaded file
Intro Date:July 27, 2010*Disc Date:June 11, 2012
Order No:BTO/CTOModel No:A1289 (EMC 2314-2)
Subfamily:Mid-2010Model ID:MacPro5,1
Std RAM:6 GBStd VRAM:1 GB
Std Storage:1 TB (7200 RPM)Std Optical:18X DL "SuperDrive"



Many thanks.

Mac Pro

Posted on Feb 19, 2015 4:19 AM

Reply
16 replies

Feb 19, 2015 6:34 AM in response to Orange215

Which drive are you trying to install it on - the internal or an external drive? If the internal, you will need to erase the drive, which means losing all your data, before you can install Snow Leopard. Do a backup before erasing. Format the drive Mac OS Extended (Journaled) and Option GUID.


How to downgrade from Mountain Lion to Leopard/Snow Leopard

Feb 19, 2015 8:55 AM in response to OGELTHORPE

The disk is a white disk with the image of a snow leopard on and it says version 10.6.3 rather than 10.6.4. Can I assume this is a retail disk and therefore not the one I need? Is there a way I can use the disk I have? I'm not sure if this is the exact disk that came with the pc but I'll hazard a guess that it isn't as it's dated two years after the mac's purchase.

Feb 19, 2015 9:00 AM in response to Orange215

I've tried to follow your advice put unfortunately the install icon has a cross through it so it won't allow it to run and I'm unable to install it on the drive. Do you know why this might be?

You can't run the installer of an older OS X version from a disk booted to a newer OS X version. You can't run the Snow Leopard installer while booted in Mountain Lion.


This is why you need to boot from the Snow Leopard DVD. Disk #1 of 2 of the grey DVDs that shipped with your Mac. Insert the DVD and restart it while holding down the "C" key. It will be a slow boot process.


If you don't have the 2 grey DVDs, you'll have to order a set from Apple The retail disk is for 10.6.3, an earlier version than the one that shipped with your Mac.


User uploaded file

Feb 19, 2015 9:00 AM in response to Orange215

That is a retail disk and you will not be able to install it on your Mac Pro.


What you might try is use it on another Mac that had Leopard or an older OSX installed on it and install 10.6.3 on it. Then use the Snow Leopard Combo Update to get it to 10.6.8. That may then be compatible with your Mac Pro.


The other option is to get duplicate installation disks from Apple customer service.


Caio.

Struggling to downgrade from Mountain Lion to Snow Leopard

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