Also in those machines, you can't run any of the good versions of OS X because of the CPU soldered to the motherboard. OS X can't see any CPU installed beyond the one onboard on those systems. You can run 10.0 and 10.1 because they still contain 603 support but beyond that, no. Since 10.0 and 10.1 are pretty useless for running OS X software, it's almost the same as no OS X at all. Some people have hacked 10.2 to work, but even on a 6500/300 it takes forever just for the desktop to appear. It works on the beige PCI Macs with a CPU slot because the upgraded G3 or G4 CPU is the only CPU that OS X sees on those machines.