User guide

SCSI Connectors
There are lots of different types of SCSI hard
drives with different types of connectors.
Externally there isn’t much variety: 25-pin,D-
shell, 50-pin Centronics, or high density pretty
well covers it all. For internal connectors it gets
much more complicated. Type of interface is an
attribute always mentioned for SCSI drives.
In order to patch the connector cables your Mac
uses into the drive you might find available it
may be necessary to use an adapter that matches
your drive on one side and your Mac interface on
the other.
Most of our older Macs have small single SCSI
drives with a 50-pin interface. The flat ribbon
cables simply connect directly into the logic
board and into the single hard drive. Later Macs
could accept several of these drives on one fifty-
pin ribbon as long as each had its own SCSI ID.
As SCSI technology changed to meet the
demands of faster data transfer and faster types
of SCSI drives became available SCSI branched
out into fast SCSI I, II, and II and often got desig-
nations like Wide, Fast, and UltraWide.
Fortunately there are SCSI adapters available,
like those shown on this page, that will enable
you to marry up different types of SCSI drives to
your system by standardising the interface of all
of the drives in your Mac. If you see bargain
drives for your Mac but can’t match up the cables
you will find that all things are possible once you
find out what type of connectors you need.
SCSI I and II with 50-pin interface
SCSI III with 68-pin interface
SCA 80-pin interface