That is indeed the case, but since the 601 and 603 don't don't
search the htab for you but rather trap to the os there's no need
to even use it! It would be quite possible (and I've been thinking
about it lately) to just have the 60{1,3} search the linux
maintained tree instead, load tlb entries from there and only
convert this tree to the ppc htab for the 604 which does the search
for you.
Be careful. Unless you have a special L1 cache bypassing load
instruction, you can end up thrashing the dcache horribly with such a
scheme.