Downgrading from Lion to Snow Leopard on the latest Mac hardware #

Booting a new MacBook Pro (Late 2011) from a retail 10.6.3 disc resulted in a black screen and a repeating 3 beep pattern. This is due to missing Sandy Bridge drivers. Apple will ship a 10.6.6 (iMac) or 10.6.7 (MacBook Pro) installer disc^* upon request which includes the necessary drivers to boot the latest models.^†

As I could not wait for the disc to arrive, here is the process I followed to downgrade a new MacBook Pro (Late 2011) from Lion to Snow Leopard (see notes below for a faster method):

Install 10.6.3 to Firewire drive connected to white MacBook (13-inch Late 2007)
Boot white MacBook from Firewire drive with 10.6.3 and update to 10.6.8
Boot new MacBook Pro from Firewire drive running 10.6.8
Clone Firewire drive to internal SSD with Carbon Copy Cloner or SuperDuper!
Boot MacBook Pro from SSD - success!

Here is an abbreviated version of Apple's Mac OS X versions (builds) for computers showing only the latest models:

Latest model	Introduced	OS originally included	OS included later
iMac (Mid 2011)	May 2011	10.6.6	10.6.7,10.7
Mac Mini (Mid 2011)	Jul 2011	10.7
Mac Pro (Mid 2010)	Aug 2010	10.6.4	10.7
MacBook Pro (Late 2011)	Oct 2011	10.7.2
MacBook Air (Mid 2011)	Jul 2011	10.7

Notes & Updates:

* These machine-specific installers can be made universal as well: Make a universal 10.6.7 Snow Leopard installer.
† I have successfully tested the 10.6.7 MacBook Pro installer DVD on a Late 2011 MacBook Pro purchased Feb 2012.
Reportedly, a MacBook Pro 10.6.8 image can boot the latest Mac Mini as well.
Roy Miller explains how to slipstream 10.6.8 into a 10.6.3 image via NetRestore. Note that System Image Utility 10.6.8 is found in Server Admin Tools 10.6.8, not in Mac OS X 10.6.8 Update Combo v1.1, as mistakenly mentioned in the "Required resources" section.
- Found a fixed and formatted version of Roy's instructions, along with a Target Disk Mode method that is much faster than using an external drive.
Recap of downgrade methods and performance notes
Apparently OS X system drives are largely universal, generally booting any Mac of the same basic generation.
Apple strongly discourages downgrading: Don't install a version of Mac OS X earlier than what came with your Mac

/mac | Nov 24, 2011

Subscribe or visit the archives.