IBM OPTIONS User Manual page 18

removed also. When no external SCSI devices are attached to the bus, the
internal cable is terminated at one end by the SCSI adapter itself, and at the
other by the termination device on the internal cable.
The following are possible SCSI termination configurations. If the SCSI
configuration consists of one cable, terminate the last device 1 on the cable.
Remove termination from other devices on the cable.
If the SCSI bus consists of one internal SCSI cable and one external SCSI cable,
terminate the last device 2 on the external SCSI cable and the last device 3
on the internal SCSI cable. Remove termination from the other devices on each
cable.
Step 6. Terminating the SCSI adapter
Termination on the SCSI adapter is controlled by software commands using the
SCSISelect. The initial termination setting is Automatic.
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IBM PCI Ultra160 SCSI Adapter: User's Guide