Unfortunately Mountain Lion will not be coming to Core Duo Mac’s. But it will be coming to the latest crop of unsupported machines. We’re currently working on a streamlined download like we did with RoaringCore 10.7, but for now, here are instructions provided by hackerwayne on MacRumors forums:
1. Get a copy of Mountain Lion, I got mine from Apple. If you’re not a dev, maybe you can get it at “the bay full of pirates”
2. Make sure you have a Mountain Lion compatible Mac, Im using a MacBook 2.4GHz Aluminum 2008
3. I have no FireWire to do target disk mode, so i removed the HDD from the MacBook White, pop it into the ML compatible Mac and install Mountain Lion like normal.
4. Get everything set up, until you reach the desktop
5. Now, remove the HDD from the compatible Mac, pop it into the MacBook White. Restart the MB White and hold down “CMD + V”. It should say “Incompatible Mac detected. Reason: Mac-F4208EC8″ the “Mac-F4208EC8″ is a unique ID for your Mac, so copy that down.
6. Remove the HDD from the MacBook White, and again, pop it into the compatible Mac, reboot back into Mountain Lion. U Now, navigate to ‘/System/Library/CoreServices’ on the Mountain Lion partition. Unlike 10.7 Lion, users delete PlatformSupport.plist. In ML 10.8 add that unique ID that you copied just now to PlatformSupport.plist. If you try to delete that Plist file, a Kernal panic will greet you during boot.
7. In PlatformSupport.plist, remember to add your model identifier, if you are using a MacBook White like me, add MacBook2,1 right above MacBook6,1. This step is important as the EFI reads this by sequence.
For MacBook 07 and 08 add this line right above MacBook6,1
For 07: MacBook2,1
For 08: MacBook3,1
For Mac Pro 06 and 07 add this line right above MacPro4,1
For 06: MacPro1,1
For 07: MacPro2,1
8. Now, boot it back using the MacBook White and confirm that the ML is booting. If you did everything right, you should be able to reach the desktop, but have no accelerated graphics whatsoever, only framebuffer. (for MacPro1,1 and 2,1 with upgraded graphics card, you should get a perfectly working ML)
9. 2 ways to perform this step:
a) Manually copy and install the right kext.
b) Use kexthelper (skip 10 – 13)
MacBook2,1 - AppleIntelGMA950.kext, AppleIntelGMA950VADriver.bundle, AppleIntelGMA950VLDriver.bundle
MacBook3,1 - AppleIntelGMAX3100.kext, AppleIntelGMAX3100VADriver.bundle, AppleIntelGMAX3100FB.kext, AppleIntelGMAX3100VLDriver.bundle
MacPro1,1/2,1 - upgrade graphics card to GT210 or HD 5770 No kext required. 7300GT untested!
MacMini2,1;3,1 iMac4,1;5,1 untested. Please try using above method depending on which graphics card you have and report back results! Thanks!
For ATI graphics card, i do not have a Mac to test them, I believe its the same, try ATIRadeonX1000.kext, ATIRadeonX1000GL.bundle, ATIRadeonX1000VA.bundle, ATI- yliadxos.bundle and report back.
10. Back to the MB white, install the kext using KextHelper and reboot.
11. After it reboots, you should be able to see a pop up message saying that the kext isnt compatible. If yes, reboot.
12. Boot into Single User Mode (Command+S ) and type the following:
chmod -R 755/Volumes/~MLPartitionName/System/Library/Extensions/AppleIntelGMA950.kext
chown -R root:wheel /Volumes/~MLPartitionName/System/Library/Extensions/AppleIntelGMA950.kext
Then remove cache and rebuilt:
rm -rf /Volumes/~MLPartitionName/System/Library/Extensions.mkext
kextcache -k /Volumes/~MLPartitionName/System/Library/Extensions
14. Working Mountain Lion on not supported system.