I used to have an S612 but had to sell it a while back. IIRC it had really rudimentary I/O and no SCSI. But I did experiment a bit with MSD which did work. Transferring banks via MIDI sample dump on a later polyphonic sampler can be grueling tedium, but since the S612 has little memory, it is not too bad. I used the info from the wiseguysynth page DieHard posted to make a Max patch long ago, but I lost it with my old system.
I did also pursue that v1.3e ROM, but besides being rare, it also includes hardware mods. So one apparently can't just download it from the net. The guy who developed it is not interested in circulating his mods for free or DIY use.
The S612 is a fun box for hands-on sound mangling. I still have a broken one which I might fix someday if I ever get the time. And maybe add CV summers so I can externally modulate the loop slider controls. It does have a lot of potential for mods, but its build is as such that one really does have to completely disassemble it to properly access the good stuff. One of the easiest tricks is using the 13-pin DIN plug on the back to break out the separate voices. Wish I had more time to play with the working unit.