So, I looked at my 'space' 44 and found it had
an RK611. That's nice,
but not helpful as I have no rk05's (yet :-)
If it is an RK611 (a 9 slot backplane with 5 hex cards in it IIRC), then
it's for RK06/RK07 drives. The interface is _very_ different to that for
the RK05.
IIRC (again), the 3 spare slots are one end of the RK611 are wired as SPC
slots and you can stick normal SPC cards in there (converesly if they're
empty, you need to put grant continuity cards in them).
Personally, I'd want ot konw why you can't get cards into the exising
backplane. It may be soemting simple like it's not aligned with the
cabinet properyl (so the board edge conenctor tabs don't quite line up
with the backpalne connectors. Try loosening the mouting screws for the
backplane and sticking a hex card (anything, you're not going to power it
up) in each end slot, then retighten the screws.
-tony