How I installed Mac OS X 10.8 Mountain Lion on my Mac Pro 1,1

In general, I'd advise against this!

That said, been running ML on a Mac Pro 1,1 for the past two weeks without issue, but there are things to note:

* You will need an upgraded graphics card, basically anything sold with a Mac Pro 4,1 or newer. I have a Radeon 5770 from my Mac Pro 5,1 which runs great.

* You will need to use Chameleon as listed below, this subs in a 64-bit EFI. It changes your boot process and you'll need a drive which is formatted MBR (legacy Windows) to accomplish this. It fakes the machine into old-school BIOS which in turn loads a 64-bit EFI and is then able to boot ML. See the linked article, it's vital you follow it precisely.

* It's processor hungry. I've swapped out the original Xeon 5160's (2x2) for a pair of X5355's (2x4). It was sluggish at times under the 5160's. I've got 12GB of RAM and a Corsair 180GB SSD in the mix which makes the machine mostly scream.

* Comparison: My Mac Pro 5,1 with 12-cores and RAIDed dual Accelsiors beat the living crap out of the upgraded Mac Pro 1,1. However, I feel I bought myself another 2-3 years of life out of this Mac Pro through moderate upgrades: Xeon X5355 (~$120 on eBay, essential you get a matched pair), SSD boot drive (240GB are as cheap as $125-$150 now, remember to get a SATA II as SATA III won't work in your Mac Pro 1,1) and of course RAM is always essential. Mountain Lion, while not officially available for your machine, is only $20.

The basic problem with the Mac Pro 1,1 and Mac Pro 2,1 is the lack of a 64-bit EFI. The systems themselves are 64-bit.

Apple probably dropped support for lack of wanting to develop 64-bit graphics card drivers for old cards which were sold with those systems. If you've updated your video card to something more modern (such as a Radeon HD5770) this hack will work, provided you need a bit of geek-fu to make it all spin. You'll need Chameleon from the Hackintosh world and a spare installed SATA drive to get started.