HowTo revert new MacBook Pro, Mac Pro or iMac to Snow Leopard

Fascinating... so what is it about the iMac (zirkenz) and the Mini that render them so different from the MBP as far as downgrade-ability? I mean the iMac can go up to i7 and more cores (?) but the Mini?

Hopefully it's something ridiculous and silly... wish I had a Mini to troubleshoot! Unfortunately, it may be that the solution is beyond the scope of Apple Discussion forums. The irony is that the solutions the Minis seek may be with the people who have figured out how to run all of these OSes on combinations of processors, video cards, motherboards, etc very very different from the Apple lot.

My buddy was running 10.5.8 -- REGULAR Leopard -- on an i7! For like 2 years! I don't remember his benchmarks but I remember thinking them good. It ran so well that he stopped using PCs altogether and bought himself a MacBook Air when Lion came out.

So while anything is possible, at a minimum these Mini-folk may have to get their hands a little dirty. It may literally come down to using bits from Mini Lion to enable the power of Mini Snow Leo. But I can't speculate as this requires considerable experimentation and geniuses that probably wouldn't be allowed on these forums.

But I'll report back if I find anything reasonable 😉

@Roy, now that Zirkenz got me addicted to Geekbench, if it's not a hassle later you could compare your Geekbenches from booting off of either/both computers' drives! He's got me curious if somehow one drive or the other is less optimized for the machine you're booting on.

That would also handle the "diskercise" of putting these babies through their paces without more time-consuming tests....

p.s. I LOVE "The Procedure" because it means I can make perfect virgin master systems and pre-install some packages to boot. I haven't had a client drive fail in awhile (knock on megabits) but when they do, I prefer to reinstall from the basics rather than simply restore from Time Machine. I mean, if the hard drive physically failed, TM is alright. But if the system has gotten itself corrupted, restoring said system from a TM gives me the willies: I don't want to "restore" the corruption too! I'd rather start fresh. So The Procedure is a great tool for the toolkit!

Keerect on the gardening, Tech Harmony!

Trying to get Roy to click over our way and share share share! Awaiting a working virtualization solution, but we'll take anything good we can get!

You nailed it in your speculation on the likely direction of the path that will lead us out of this mess! It will probably take some kind of virtualization solution, either a full "virtual machine" or some code bottles similar to Wine, to get SnoLep up and jumping over the code gaps in the most recent, committed, "Lion"-only Macs.

Hi all,

Here is a quick and dirty revised copy of the Roy Method with contributions from all those involved including screen captures for pre-cursor steps as well as steps A&B - most are probably ok with step C, so it is modified very little and has no screen captures. I did this very quickly, and have the original for those who want to add, mark-up, correct me etc, and please do so.

Thanks to all who have made this a viable solution.

http://www.mediafire.com/?ni82ava3hfdd0v8

Josh

i have to agree that roy's method is actually my favorite since it gives you a restore file that you can use over and over. It makes it simple and easy, especially if you have to do multiple systems or have to start over.

Roy you are absolutely right about the TDM method and i said so from the begining but at the time it was just a theory and what i suspected. From what i understand that geekbench tests processor and memory. Perhaps there is a faulty part in my imac. I can't use Apple Hardware Test because it is not installed with any of the methods so pressing D at startup does nothing and since there is no restore disc to pull it from, i can't use Apple Hardware Test.

My restore file was created on the new imac i was downgrading and only the final restore .dmg file was copied to the bootable clone. But since the clone was created using TDM via a macbook and then created with carbon copy cloner of the imac all updated, i wonder if when i used the clone to boot and restore if it saw my clone as a macbook. If so that would mean the bootable system you use to restore does impact what gets installed so essentially it would explain 100% why TDM method=Restore file (roy) method. The only way for me to test this theory is to TDM another system with exact specs then restore. Sadly i don't have such resources and if i did it would be easier to just clone that system and restore to my system.

So i think the system disc i ordered is lost in the mail and i guess my only option is to to go to Apple. Its gonna be fun lugging that into the mall with everyone staring at you then explaining that you violated the book of jobs by downgrading. Depend on who you get i suspect i will either be told it can't be done or see this is what you get and will continue to get for downgrading and my only option is to use Lion. Maybe i get lucky and they fix this issue.

Thanks, Roy, Yes, we agree that those Macs never had, and never will have, the code needed to support Snow Leopard -- and that Snow Leopard will never be released in a version that contains code to fill in the gaps in chips, drivers, and other hardware challenges so that the "Lion-only" Macs could run SL.

Being kinda slow in the head, that's precisely why I expect a non-Apple solution to be forthcoming fairly shortly. We shall see! -- much of what follows depends on whether Apple actively stands in the road by, for instance, refusing permission to run Snow Leopard on a virtual engine under Lion. Even then, I expect hacks to be developed and to slip out into the community and be circulated.

This is a kind of "brain surgery," but at least we know which neurons have a problem and can figure out what rewiring is required to produce a result. Then, it takes thought, motivation, effort and time. I'm optimistic.

Just trying to nudge, nudge, nudge the process along. Giddyup!

@Josh WOW! Once I clear off my desk, I may just try a run-through of your guide.... great work!

I wouldn't mind a mark-up copy if you're offering... I was scheming on how to get this into a Wiki/HTML format and this is already a tremendous start.

Thanks so much!

okay i have some interesting information:

I contacted geekbench asking if there was a bug in 2.2 and gave them my info, details and results, etc. They gave me a link to 2.13. Okay so i ran it and 2.13 gave 54xx and 2.2 gave me 53xx. They said maybe there is some hardware or software issue and asked if had tried it on lion.

I decide to install Lion on my imac using the recovery thumb drive i created. I paritioned 500 gb for this purpose and installed lion. I ran Geekbench 2.2 and 2.13 again under lion. This time 2.13 gave me 10230 and 2.2 gave me 95xx. So this proves that 2.2 is slower than 2.13. So clearly something was not right in the SL install either TDM or Roy's method or Apple is neutering the system.

Next i created a bootable clone of my imac running lion 10.7.1, booted of that ran geekbench 2.13 and 2.2 and got high scores same as above : 102xx and 95xx respectively. Then I erased and restored my sl partition with my roy method .dmg file. Ran thought setup again. It worked fine and i reran geekbench 2.13 and 2.2. I got the same low scores as above!!!. So this proves that system you use to restore the file using roy's method does not matter because i was on a lion clone and restored from that and it did the same thing.

Now i am rebuilding on the imac running lion 10.7.1 the restore file using Server Administration Tools 10.7.

I redownloaded 10.6.8 v1.1 updater on the imac running 10.7.1 and will recreate the .dmg file from the mac box set 10.6.3 disc. This will all be done on the imac running 10.7.1, then i will copy the resulting restore file to my 10.7.1 clone and restore my imac sl parition again and will report if there is any difference. This should prove if the system you build it on matters or not and whether the resulting file supports core i7 after aug 25 or perhaps it could prove that Apple has indeed done something in firmware to neuter the system This and my previous efforts should prove once and for all that neither the TDM method nor Roy method works in SL downrade that gives you 100% performance. Will report back later this evening......

Super thorough!!!!

Wow.

Okay... Glad your hardware is fine.

So it sounds like even though your iMac does not have a little "New" flag on it in the Apple Store, that it still didn't make some cut that the MBP's seem to have made.

Possibly only the Macbook Pros and Mac Pros are running at full speed on Snow Leo. The New-mini folk and some (most? all?) iMac folk must be in the same boat.Grrrrr.

If you look for your iMac at http://buyersguide.macrumors.com/ it looks like there were multiple firmware updates for graphics and, as an aside, apparently Apple rigged the hard drive so you can't easily replace it yourself. Usually they're not this draconian (although opening some of these babies up isn't always a picnic).

You may have to reach out to the open-mac community to crack this nut. It's probably not really firmware that's in your way, but a combination of kernel, drivers (kexts)... the only way to get your iMac to work like a Mac, may be to start treating it like an Intel box!

Just saw this thread and it's quite long.

Can someone please summarize the results, limitations, models and methods to reverting a new Lion factory Mac to Snow Leopard?

Thank you! 😀

Okay, so Server Admin Tools 10.7 does not let you create a netinstall image-option is grayed out (see attached pic) and 10.6.8 does not install on a 10.7 system. So i can't use lion on my imac to recreate roy's file. But see the red text in the image. It did not accept the mac box set dvd nor the image file created from it. So what install DVD is it expecting? Lion does not have one.

So i guess my only option now is the restore disc which seems lost in the mail or an apple store visit.