Install Disk for Snow Leopard will not boot on an iMac 27in

The currently-shipping mid-2011 iMacs can boot Snow Leopard, even those that shipped from the factory with Lion preinstalled. The retail "universal" Snow Leopard DVD may not be able to boot them, however, as it has a version of Snow Leopard that does not include the necessary components for these iMacs. That makes getting Snow Leopard onto them and patched up to 10.6.8 a little tricky, but not impossible - just have to use another Mac to do the install with the new iMac in target disk mode, or restore from a bootable backup.

I created, though, a bootable flash drive from the actually recovery install DVD that came with my iMac (which I have previously used to recover my iMac to Snow Leopard, pre-Lion). That is really odd to me, that my iMac will not even boot from the recovery DVD that came with the iMac after Lion.

As to the option of doing the install in target disk mode, or restoring from a bootable backup, I don't know how to try either of those. How do I create a bootable backup for SL? My Macbook is running 10.6.7, so maybe I could create one from that computer.

My first gen 27 inch iMac (Leopard -> Snow Leopard (installed from DVD) -> Lion) won't boot the Snow Leopard install dvd. Fortunately I have a 24 inch intel still on Snow Leopard. I need SL for some dev work ... and it is disappointing that perhaps the boot was flashed (maybe for recovery of Lion support) but disables Snow Leopard installs from the facory sold media.

Just speculation, but it seems a common problem.

I had the same thing just happen to me after my iMac became unresponsive while I was I installing Silverlight in my Win 7 boot camp partition. After several failed attempts to boot normally (spinning wheel froze) I inserted my SL disk and attempted to boot from it. But like you I got the perpetual white screen. After thinking for a while, I decided to reset both my PRAM and NVRAM. After doing this, I was able to boot into the SL disk successfully.

I'm not sure which reset worked, but I'm glad I'm back running again. Good luck.

i was having similar problem on 13" MBP i5 (early 2011). The mac os x install disc is 10.6.6 version 1.

try pressing Option when boot up, select the DVD and press CMD V to go verbose mode.

What i saw was alot of disk1s0 errors. However the DVD drive is working properly before so it must be the disc's problem. But the disk reads properly in my other PC...

I then clone the disc onto another Dual Layer DVD with x4 speed. And the cloned disk works without a hitch.

Very strange problem. I believe the original disc was not burned properly by Apple.

I would like to report back, I was able to install Snow Leopard (10.6.8) by using the target disk mode and running the Snow Leopard install disk from a different Mac computer. After running the retail Snow Leopard install, I updated with the combo installer to 10.6.8 and also updated all the other Software updates that showed up.

I now have snow leopard running on my iMac 27" that came with Lion pre-installed.

Fyi, I could not erase and reformat the SSD partition from the other mac, I had to log into lion to partition and format it before trying to run the Snow Leopard install.

So I hereby declare this thread solved.

can you share how exactly (not very clear) did you do this? i need to do the same for my 2011 macbook pro.

thx.

Target diskmode is entered at boot time. It requires a firewire connection between the two machines although I have heard that thunderbolt works too, but not personally verified it.

When you boot the target computer (with the Install DVD in its drive) hold down the "T" key until the firewire icon appears. The other computer can now access the drives of the other machine as if they were locally mounted as a firewire device. SO the DVD should now appear.

However, there is no gurantee that a Apple Machintosh that shiped with Lion will be able to have Snow Leopard installed.

Oh, i see, this is how you do it. OK, thx.

Not a very good solution when it requires you to own or buy another $$$ Mac.

Why does Apple sell these DVDs without telling owners the caveats - they have to know that some users would buy them to install on new macs.

Now I have to once again call Apple due to non working product. If it wasn't for Macs prevalence in video editing I wouldn't have bought this overpriced piece of garbage!

It is not normal to downgrade the OS. But I also know that if you don't have a second Mac, or don't want to rent one, you can take the iMac into an Apple store and the folks there will likely help you.

As to being overpriced? Are you serious. Compared feature by feature and Macs are cheaper. Less configurable for iMacs, but cheaper overall. And with the 2011 iMacs with Thunderbolt you can purchase an external chassis if you need one.

The PCs I've used that are similarly priced or are bargain PCs are flimsy, have poor fit and finish, and worst of all run Windows. An inconsistent, fragile OS that is a malware magnet. Mac OS X is leaner and more thought out. And most of all it is consistent.

You should also consider going to your software vendor to see if they have a Mac OS X Lion upgrade. The original post did not mention why they were downgrading, but it is not commonly needed. I run several packages originally released under 10.4 or earlier. And if it is because you need Rosetta (ppc emulator) then your software vender is slow to upgrade, but if you search you can see how to do an unsupported installation of Rosetta on Lion.

I have bought my mac in july 2011 and i lost the original snow leopard DVD and i have problem with Lion coz doesnt support properly my external HDDs (i dont know why)... So i need Snow leopard!! Where can I replace the original DVD from?

Call Applecare with the serial no. of the Mac and they can replace the original discs for a shipping and handling fee.

I can confirm that this was the solution for me.

Had the exact same problem mentioned by everyone else. My problem is that I had been trying to boot up from the Snow Leopard disc I had purchased for my Macbook Pro.

The solution was booting from the grey OSX Install disc that came with my iMac. Worked exactly as it was supposed to.

Cheers @saxon !

Does anyone know if the downgrade procedure will work if I want to install SL 10.6.7? It's mentioned twice in here that using the target disk mode method works if your end goal is 10.6.8, but because of some app needs I need to be running 10.6.7 or earlier on a refurbished imac I5 from may 2011 that came with lion. I can't tell from the internet research I've done (this stuff is all pretty foreign to me) whether or not this seems feasible. Any info would be appreciated.