Northstar disk controller family tree

I'm starting work on adding support for a Northstar disk controller to my Sol emulator program. Before I start writing code, I figured I'd see if anybody could clarify the relationship of the various Northstar disk controller boards I have either seen on ebay or I've seen mentioned on the web: 1) "Micro-Disk System MDS-A" 2) "MICRO-DISK MDS-A-D DOUBLE DENSITY" (I have the manual to this) 3) MDS-AD2 4) MDC-A2 5) MDC-A3 6) MDC-A4 (I have one of these but haven't tried it yet) ... and others? I assume that #3 is just a different name for #2. How do they compare? Does anybody have programming/technical docs for the ones that I don't have? If it isn't a stretch (and I'd assume it isn't, since they are all from Northstar), I would like to add support for the other disk controllers, but without the docs that won't happen. My real Sol has a "Micro Complex Phase Lock II" disk controller in it, which is compatible with the MDS-AD2 (I think) [ single/double density disk controller ]. I also have an MDC-A4 board, but no docs on it, so I haven't played with it. Thanks for any information, code, tips, vague recollections... ----- Jim Battle == frustum(a)pacbell.net