Because the motherboard itself is based on an architecture called NuBus. OS X is just not capable of booting on a NuBus system and will only boot on a PCI architecture board.
Therefore OS X will never boot on a 1400, regardless of how upgraded it is.
It would be like trying to run Windows NT PPC on a Mac, the CPUs are the same, but the way the system pretty much handles everything else isn't the same and in turn isn't compatible. It just doesn't work.
Therefore OS X will never boot on a 1400, regardless of how upgraded it is.
It would be like trying to run Windows NT PPC on a Mac, the CPUs are the same, but the way the system pretty much handles everything else isn't the same and in turn isn't compatible. It just doesn't work.