Booting from external FW cdrom

[BuG <bug@fastwebnet.it>]

I'd like to be able to boot from an external FireWire cdrom directly
from openfirmware.
Is it possible?
What is the syntax for yaboot, or which shortcat do I have to use?

(I have a pismo and the external cd is a LaCIE cd-rw)

Thanks

BuG