Will a downgrade work for you?

So you want to downgrade your new computer from Lion to Snow Leopard?

Well as of 9-18-2011:

  • Early 2011 MacBook Pros both allow the downgrade and appear to run at optimal levels after doing so.*
  • Mac Pros allow the downgrade and at this point I believe they run at optimal (asserted but unverified)
  • Mid 2011 iMacs allow the downgrade but it appears they run at half-speed, scoring half as well on benchmarks (e.g. Geekbench or Xbench) ... still very fast!
  • Mid 2011 Minis also allow the downgrade but also appear to run at half-speed.
  • Mid 2011 MacBook Airs may not downgrade at all at present because they never shipped with Snow Leopard.

*Note: Apple may come out with MacBook Pro updates this week and so it is unknown if these methods will still work. This will be true of any hardware update to any of these machines.

Without getting too deeply into this, the idea is that if your model computer was shipping with Snow Leopard before Lion came out, then you should still be able to run Snow Leopard. Find your Mac here and see if it originally shipped with Snow Leopard: http://support.apple.com/kb/ht1159

The problem is that the version of Snow Leopard that these machines were running was a modified version of Snow Leopard optimized for your given machine. You can't just put a retail version of Snow Leopard (10.6.0 or 10.6.3) onto these computers because you won't even be able to boot the install disc.

Our goal is to get your Mac up to Snow Leopard 10.6.8 directly, when the majority of advanced features were included for most Macs.


So how does one go about this?

The main subject of this site has been dubbed "The Procedure" and it entails making a master 10.6.8 installer image that can then be "restored" to your target Mac's hard drive. We are indebted to user Roy for bringing this method to the masses. This is where we've been fleshing out this method: https://discussions.apple.com/thread/3264421

However, there are two other methods that you might wish to consider:

1) Since you are still under AppleCare, you should have good luck requesting the Snow Leopard factory install disc for your machine if one existed (here again). They are 16$.

Some people have even had luck having the Genius Bar to do the downgrade... YMMV as to whether they will do so.

The factory/restore disc will generally give you the best results because it was designed for your Mac. User @zirkenz was able to get his iMac running at full-speed only after utilizing his factory restore disc. I assume it must have contained specific files to unlock his processor's full potential.

2) The "Target Disk Mode method" (or "TDM Method") is also described on this site although you may find better steps on Google. Theoretically this should work as well as the 10.6.8 system image restore procedure but many of us prefer using "The Procedure" to create the 10.6.8 system image because, once created, it is easy to re-use it for reformats, among other things.

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Whatever route you go, you should back up your Lion partition
and/or Lion Recovery disk before you begin.

Depending on how you partition your target computer later, you may not have to do this step but doing so will ensure that you can later upgrade to Lion if/when you are ready.

If you want a Lion Recovery Disk, follow the instruction in this knowledge base article: http://support.apple.com/kb/DL1433

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The Future

Who knows how long these methods will work as Apple rolls out firmware and hardware updates. For the MacBook Pro line, it may continue to work very well but there are no guarantees. Be cautious with firmware updates as Apple releases them.

There is a Mac Mini Apple Discussion forum dedicated to sorting out how to get Snow Leopard running on Minis. Some may be at the point of trying to run a virtualization of Sleo under Lion. You'll have to explore the forum. For a native solution, my feeling is that they should reach out to the Hackintosh community as they seem expert in getting OSX running flawlessly on countless Intel architectures. But this is beyond the scope of an Apple Discussion forum ;)

 
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