Instruction manual

PDI-00440-70, Rev. A01
Appendix A - SCSI Termination
SCSI TERMINATION USING AN EXTERNAL TERMINATOR
The SCSI bus must be terminated at each end of the cable. The CPU board terminates one end of the bus.
The preferred method of terminating the other end of the SCSI bus in an AMOS computer is the
installation of an external terminator. In April 1993, the external SCSI bus terminator became standard
on all AMOS computers. Using an external terminator makes installing an add-on subsystem (like a
portable CD-ROM drive) easier, eliminating the need to remove terminators from a SCSI device located
in the host computer. On newer AMOS computers, including all models which support Wide SCSI
operation, this external terminator
must be
an “active” terminator.
An active terminator for the Wide SCSI bus (PRA-00222-20) is included in the Wide SCSI upgrade kit.
To use the external terminator, make sure none of the SCSI peripherals inside the computer are
terminated. The termination power for the SCSI bus is provided by the CPU board.
If you are using the external terminator and one of the SCSI devices inside the computer also has
its terminators installed, you will experience problems.
The external terminator is shown in Figure 5, below:
PRA-00222-20
EXTERNAL SCSI BUS
TERMINATOR
SCSI CONNECTOR
ON BACK PANEL
Figure 5: Active External Terminator Installation