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I purchased a refurbished iMac "originally released May 2011" from Apple ( ), hoping it'd still have Snow Leopard on it.

Ended up having Lion on it. My Googling says it originally came with 10.6.6, so it definitely supports Snow Leopard, but I guess in the refurbishing process they upgraded it to 10.7 and now I can't get it to go back.

How can I downgrade an iMac12,1 from Lion to Snow Leopard?

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You can do this if you have an older Snow Leopard-compatible Mac.

  1. Put the new iMac into Target Disk Mode and connect it to the older Mac with a Firewire cable. Its hard disk should mount on the desktop of the other Mac. (Hold T at startup to enable Target Disk Mode)
  2. Boot the older Mac from the SL DVD that came with that Mac and install onto the new iMac's hard disk.
  3. Before Rebooting the iMac Download and install the Mac OS X 10.6.8 Combo Update while booted from the older Mac's normal operating system. Make sure to target the new iMac from within the Installer.
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You could always wipe (format) the hard drive and reinstall if you have a Snow Leopard disc available.

I'd recommend not bothering, though. Lion is much better than Snow Leopard in so many ways.

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Are you sure that'd work? When I tried booting from a 10.6 disc (with Lion still installed), it said Unsupported CPU. Apparently I need a disc with 10.6.6 or greater, but we don't have one... – David May 31 '12 at 18:50
Ah. Yes, the old disk might have problems. You could boot the iMac into Target Disk Mode and install Snow Leopard onto its hard drive from an older computer that the 10.6 disc recognizes, then install the 10.6.8 combo update from that other computer, then boot the iMac (and install any other updates). – CajunLuke May 31 '12 at 18:58
Any detailed instructions on how to do this? I'm kind of wary about wiping the drive, in case things go wrong, we have no Lion DVD since refurbished iMac's don't come with discs. – David May 31 '12 at 19:00
You can make a bootable Lion USB disk using instructions on Apple's support site (the link is somewhere here at Ask Different). I still think you should get used to Lion: it really is better. – CajunLuke May 31 '12 at 19:08
When you completely format your hard drive, there shouldn't be any software or logic which stop you from boot from Snow leopard. You can Insert a Windows-CD, and before you "install", you can format the complete hard drive. Then insert the Snow Leopard CD and install it. – gruberb Jun 2 '12 at 7:35

It's very rare that a Mac will support an earlier version of OS X - that is, a version that was released prior to the release of the machine in question. The drivers alone would be a pain, you'd probably have to do some crazy stuff with kexts (for some really good info on that kind of deep magic, check out the Hackintosh Support Communitites section of for links to some smart people and conversations). In any case, it will likely be quite difficult to get it working. However...

If you really want to, you might as well try! Don't worry so much about wiping the drive; since the Mac came with OS X Lion installed (even though it originally didn't), and as long as you have installed all your Software Updates, you can use Lion Recovery to reinstall the entire OS, even to a blank drive (useful in the case of drive failure or replacement/upgrade).

Also, target disk mode would be a good place to start, I'd imagine. Your Mac will actually prevent you from booting from an earlier version's install disc, so you'd have to have a disc with 10.6.6 or later on it. For example, booting from the current Snow Leopard retail disc (10.6.3) won't do it.

Your best bet is probably to see if you can find anyone selling the restore disc that originally came with your model. Try searching eBay/craigslist for your model number and good luck!

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As that model did initially come with Snow Leopard installed, you just need to find a SL restore disc that's specific for the iMac. eBay is probably your best bet.

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You'll need to boot from the SL install disk to perform a clean install.

  1. First, insert the SL disk in dvd drive, the install window should open but if not double click on the mounted drive to open.
  2. Double click the "install OSX" icon.
  3. You should have a couple of options now, one of them will be "utilities". Click utilities and the SL install disk will tell you that you need to restart to use utilities from this disk. Hit the restart button.
  4. Once you restart you'll have to select your language then you should get the utilities option again. Select utilities and then "Disk Utility"
  5. Select your hard drive from the left panel of the disk utility screen.
  6. Click on the erase tab, make sure format is set to "Mac OS Extended (Journaled)", then click erase.
  7. Exit the disk utility screen and follow the instructions to install Snow Leopard.


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