Loading Snow Leopard on an older, upgraded (cpu) Mac Pro..

[Buzz]

Not sure if it's still possible, but several years ago I talked the Apple help folks into sending me their "white label" version of the 10.6.7 installer DVD... actually must've done a really good job, because they ended up sending me two of 'em. Made setting up the last of the SL'able Macs a lot easier. Of course in the intervening years, like others have noted, making a master 10.6.8 install for SL'ing machines has been the easiest of all. Ask around your 'hood, somebody probably already has a 10.6.8 USB stick and/or disk image you could borrow.

Going the other direction... I wonder if you could still run Leopard 10.5.x on a Mac Pro 4,1 that has been upgraded to a 5,1? Intuitively, I think it might work depending on the processors and GPU in the machine... interesting to try to figure out what the fastest Leopard machine could be.
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[hal]

GGD wrote:
If you have another older Mac that can boot 10.6.3, then you should be able to use it to install 10.6.3 onto the drive, then run the 10.6.8 combo update and then the MacPro should be able to boot from that drive.

You could do this by putting the MacPro into Target Disk Mode, and connecting it to another Mac via FireWire to do the install and update, then shut everything down and boot the MacPro.

yeah, what he said. Not a big deal - easy workaround assuming you have the extra bits of hardware.

[ka jowct]

I can assure you from personal experience that you can use the retail Snow Leopard disc to install it on a 2010 Mac Pro. If it is a 2012, then you'd need to have a computer capable of running an earlier system so that you could use it to get SL installed onto a hard drive that you can then install in the 2012 Mac Pro. The 2010 and 2012 models are both identified as 5,1. Both can boot from Snow Leopard drives.

Actually, even the original 10.6 retail disc will work with the 2010 model, not just the 10.6.3 retail. I was assured by a very savvy guy in Apple phone support that my retail Snow Leopard disc would work with my 2010 Mac Pro, and he was absolutely correct.

[AllGold]

Late to the party but no one has asked this yet...

Do you already have 10.6.8 on a hard drive? If so, you can either install it in the Mac Pro or clone it to a drive or partition on the Mac Pro and it will be bootable. (I'm speaking from experience doing exactly that with a 5,1)