PReP was the PowerPC Reference Platform -- trying to create a
common system design for PowerPC systems.  It was superceded by CHRP --
Common Hardware Reference Platform.  CHRP always uses OpenFirmware.

	I believe that some PReP systems can be made to look enough like
CHRP systems so that CHRP boot images will run.

	A lot of new systems are deviating from the exact CHRP standard,
but still provide the OpenFirmware boot environment and are mostly CHRP
compatible -- they are CHRP compatible but not CHRP compliant.

David