This is the FAQ for the PowerPC port.
What kernel to use ?
Benjamin Herrenschmidt maintained a PPC-specific branch for a long time. More information can be found on ppckernel.org.
Use of 2.6 is recommended for new hardware, as support for PPC hardware has been discontinued in 2.4 series. Using 2.4 kernel is _strongly discouraged_
yaboot isn't booting my initramfs on XFS partition
This is a known bug of yaboot 336993 which prevents an initramfs on /boot on XFS filesystem to properly boot with this error:
"VFS: unable to mount root fs on unknown-block(0,0)"