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Installing the A5150A Adapter
SCSI Bus Termination
Chapter 2 29
SCSI Bus Termination
The devices that make up the SCSI bus are connected serially (chained
together) with SCSI cables. The first and last physical SCSI devices
connected on the ends of the SCSI bus must have a set of resistors called
terminators. All other SCSI devices on the bus must have their
terminators removed or disabled.
NOTE The A5150A host bus adapter is also on the SCSI bus. Termination of the
host bus adapter is automatically enabled when it is connected to the end
of the bus.
Low-voltage differential peripheral devices are usually terminated with
external terminators; however, they are sometimes terminated with
jumpers or with a switch on the peripheral. Refer to the peripheral
device manual to identify the termination setting of each device and how
to change it.
Auto Termination Information
Two versions of the A5150A SCSI PCI Host Bus Adapter (HBA) will be in
the field beginning approximately January 2001, with the release of a
new version of the HBA. The older HBA has part number A5150-60001
and the new HBA has part number A5150-60101. The new HBA (also
known as the jumperless A5150A) does not contain pins and jumpers
used for manually configuring auto termination. On the jumperless
A5150A, the default power-on setting has auto termination enabled. If
you have the older adapter (A5150-60001), do not change the position of
the jumpers; leave them as they were when you received the HBA from
Hewlett-Packard (open - not jumpered). Auto termination in both
A5150A HBAs—the A5150-60001 and the A5150-60101—is now
controlled through commands at the Boot Console Handler (BCH)
prompt. To use the auto termination feature of both A5150A HBAs, you
must have the correct version of the Processor Dependent Code (PDC) on
your system. The correct PDC versions are shown in Table 2-3.