My PowerMac G5 is a dual 2.3 GHz PPC, 300 GB hard disk, 4 Gb RAM running OS X 10.5.5.
I added a new SATA Hard-disk, installed Ubuntu 8.10 PPC64 server on it, configured it for dual-boot Linux | OS X.
I was only able to boot into OS X once.
I can mount the OS X partition under Ubuntu...