IBM RS/6000 - Manual (Page 168)

7.3.3 SCSI-2 F/W Differential PCI Adapter Terminators
This table describes the SCSI-2 Fast/Wide Differential PCI Adapter terminators.
Table 31. Terminators for Differential Installations
M/T F/C Part
Number Connector Terminator Description
DE
External
devices part of
cable F/C 87G1356 50-pin low
density 8-bit external bus terminator
DE
External
devices part of
cable F/C 61G8324 68-pin high
density 16-bit external bus
terminator
7.3.4 High-Availability Multi-Initiator SCSI-2 Fast/Wide Differential
Cabling
This card has on-card SCSI terminators that must be removed before the adapter
can be used in a high-availability configuration. The high-availability configuration
is implemented by removing the three on-card differential terminating resistors
(labeled RN1, RN2 and RN3) on the adapter, then attaching the middle leg
connector of the high-availability configuration Y-cable (FC 2114, PN 52G0173) to
the adapter 68-pin external connector. The remaining two legs of the Y-cable are
then used to attach other systems and devices to the SCSI bus.
If the SCSI-2 F/W adapter is at the end of the SCSI bus, the shorter leg of the
Y-cable must be terminated with the appropriate terminator (refer to Table 32 on
page 145).
With this configuration, if a Y-cable is removed from one adapter, the other adapter
can still use the SCSI bus. The bus remains properly terminated since the Y-cable
with the attached external terminator is still connected to the SCSI bus. The
adapter from which the Y-cable was removed is no longer terminated and may fail
diagnostics due to the lack of a terminator.
The following figure shows an example of high-availability cabling with external
disks.
144 Introduction to PCI-Based RS/6000 Servers