All Macs w/ PCI have Open Firware. Whether or not the implementation is modern enough to support Yaboot is another matter. The distinguishing difference between Old World and New World Macs isn't the presence of OF (though you could argue the OF version is important) but rather the absence of the Mac OS ROM from a hardware SIMM. New World Macs load the Mac OS ROM from a file on the hard drive.

Peace,
Drew
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Power to the PowerPC!