>It appears that the first slot in the `mem' list (/memory's reg
>property) is permanently empty (i.e. size 0) on my machine.

This problem was solved in ofw_machdep.c rev. 1.6.

If you still need, I've put my Cube kernel at
ftp://nandra.iri.co.jp/pub/NetBSD/macppc/netbsd.cube.gz