The SCSI5034 board adapts
the Synclavier D24 SCSI controller card (the oldest/most common
versions, not the relatively rare D24/50 cards that came later) to
standard 50-pin SCSI cables and standard 50-pin SCSI drives.
This, for example, makes the D24 SCSI-186 the exact functional
equivalent of the D24/50-787, just by fitting the SCSI5034 on the card.
The SCSI5034 board also gives an advantage over any
of the later D24/50 cards: It has proper a 50-pin ejector header on it,
so that the very wide and tight fitting 50-pin cable connector can be
easily pulled straight off the card without breaking or bending any
pins (a D24/50 with completely straight pins has probably never been
seen here). The D24/50 cards from NED always had the blue connectors
with the stupid metal latches that are absolutely guaranteed to break
off, and being metal and electrically conductive, aren't something good
to have bouncing around loose inside a machine full of circuits. These
new ejector headers don't break. This board is actually just a chip off
the new Synclav.com D24/50-1014, which also has proper ejector headers.
The older D24 SCSI controller card uses
a stupid 34-pin SCSI connection that wasn't standard to
anything, ever. It was proprietary to NED and was never documented
anywhere (and still isn't). There was never any such thing as 34-pin SCSI, and the use of it
required adapters everywhere, even inside their own system, either SLSI
boards (inside all NED ATS 80mb SCSI Winchester drives and inside the
black box magic adapter unit that connected the optical drives to the
system) or complicated and fragile adapter cables (which private techs
made to avoid the cost of the black box). This was probably meant to confuse
people and prevent them from buying disk drives, cables, etc. from
1987, an ATS 80mb SCSI Winchester drive from NED was $7,500. This
pricing wasn't exactly consistent with the rapidly falling computer hardware
prices in the 1980s.
Cards with stupid non-standard pinouts were an important part of protecting this pricing scheme.
NED later gave up on this, the later D24/50 cards had standard 50-pin SCSI connections like everything else in the computer world, as did some external NED drives, though NED rarely used external hard drives or floppy drives after 1988.
The SCSI5034 is a small board that snaps onto a standard early D24 SCSI controller card: