By design it is not possible to install anything better than OSX 10.7.5 on a MacPro 1.1 or 2.1. Apple decided to abandon support for hardware that does not have a 64 Bit EFI bios and these machines only got a 32 Bit EFI. But there is a way to overcome this limitation by using a 64 Bit EFI wrapper. Well it all boils down to only a single file that needs to be replaced. It is called ‘boot.efi’.
To get my Mac on Yosemite I basically followed the guide from this thread. It probably has a bit too much information on it which makes it a nightmare to extract what you actually need. So that’s why I wrote this little tutorial.
The whole task is probably a lot easier than you might think. There is a tool called ‘SFOTT‘ that patches a downloaded version of Yosemite and at the end you will get a handy bootable USB thumb drive. The tool downloads the boot.efi that contains the EFI wrapper (Piker Alpha’s bootloader) and replaces it with the original. All you need to do at the end end is to install Yosemite from the thumb drive. I updated from OSX 10.7.5 and all went well. Here is a nice video tutorial, that shows all necessary steps to create the bootable humb drive:
The script was not happy with one Yosemite download I got from some ‘special’ sources. The script memorized stuff and got confused. If it fails for you, uninstall it, clean /tmp and check all other possible places for configuration leftovers in your home folder. There might also be some process that belong to it that can get stuck, a reboot is the easiest solution. Once all leftovers are cleaned, install it again. The creation process takes long (~40 minutes).
Be aware that you might not be able to boot the thumb drive from the front USB ports. Use the ones on the back of your Mac! Hold down the option key after turning on your Mac and select the USB drive as boot source. The installation is a standard Yosemite installation, nothing special here. Your boot.efi is already patched and that’s really all you need. You can just start using it once the installation has finished!
But there is one potential hardware stumbling stone you need to get sorted before. If you are still on the stock Nvidia Graphics card you got a problem. Yosemite (also Mavericks) does no longer support these cards. You won’t have any acceleration and might also have to deal with weird artifacts. I can recommend to use the ATI 5850 or 5870 and flash it as I did.
To be safe from updates, install the PikeYoseFix script, it overwrites the boot.efi at every boot with the patched one. So even if an Apple update messed with it – it wouldn’t matter your are safe!
I can’t complain about performance. If your Mac Pro feels slow – get a SSD drive. Its really worth it!