Cumana ram disk board?

[Oldsmobile_Mike]

I'm guessing this question has come up before, but I couldn't find very much on the subject.  So, WTH is a Cumana Ram Disk Board, looks like ST-506?  Guess there's no way this could be modified to add a CF card inside an A500 with it, is there?  ;-)

http://www.ebay.com/itm/Amiga-500-Hard-drive-and-memory-expansion-board-Cumana-Ram-disk-board-rev-4-/400344763088?pt=UK_VintageComputing_RL&hash=item5d36684ad0