LSI 21003 - Manual (Page 23)

Detailed Installation Procedure 2-7
For convenience, Channel A also has a 50-pin narrow (ribbon) connector.
Some internal cables come with an SE/LVD terminator on one end. This
end should be furthest from the host adapter.
All external SCSI bus connections to the LSI21003 are made with a
shielded, 50-pin high density cable (see
Figure 2.3 ). The connectors on
this cable are always keyed to ensure a proper pin-1 connection.
Figure 2.3 SCSI Cables
SCSI Cable for Internal Connections
SCSI Cable for External Connections
68-Pin High Density
50-Pin High Density
and/or
50-Pin Low Density