IBM RS/6000 - Manual (Page 161)

Chapter 7. SCSI Cabling
It is very likely that you will face problems regarding configuration and installation of
SCSI adapters and devices.
SCSI cabling can be one of the most confusing topics to face. Lots of questions
always arise: How many SCSI devices can be attached to a single SCSI adapter?
What are the right cable features to attach more SCSI devices on the same SCSI
chain? What is the right SCSI cabling for an HACMP configuration?
In this chapter we are going to describe the main SCSI cabling features used with
PCI-Based RS/6000 Systems, in order to answer some of the questions written
above.
We will describe SCSI cabling of the two PCI SCSI adapters supported by the
PCI-based RS/6000 servers:
SCSI-2 Fast/Wide Single Ended PCI Adapter (FC 2408)
SCSI-2 Fast/Wide Differential PCI Adapter (FC 2409)
Note
Refer to Chapter 2, “PCI-Based RS/6000 Server Hardware” on page 11 for
general information about supported SCSI adapters on PCI-based RS/6000
servers, or refer to
Adapters, Devices, and Cable Information for Multiple Bus
Systems, SA38-0516-00, for specific SCSI cabling information.
7.1 General SCSI Considerations
Before describing SCSI cabling features, it is necessary to understand the following
primary specifications of SCSI technology:
Maximum SCSI bus length
SCSI terminators
SCSI device addresses
SCSI bus width
7.1.1 SCSI Bus Length
SCSI bus length is defined as the distance between terminators at either end of a
SCSI bus. The SCSI specifications allow the following maximum bus length for
each SCSI bus:
SCSI-2 SE : 6 meters (20 feet)
SCSI-2 Fast/Wide SE : 3 meters (10 feet)
SCSI-2 Fast/Wide DE : 25 meters (80 feet)
For configurations using both internal and external cabling, length restrictions apply
to the length from the end of the internal cable to the terminator on the last device
on the external bus.
 Copyright IBM Corp. 1996 137