A
SCSI ID Numbers
The information in this appendix is for technical users who want to create
custom configurations.
The small computer systems interface (SCSI) is an interface designed for
connecting disks and other peripheral devices to computer systems. SCSI is
defined by an American National Standards Institute (ANSI) standard and
used by many computer and peripheral vendors throughout the industry.
Up to eight SCSI devices can share an SCSI bus, which is a cable. All data
is sent back and forth on the cable. Each SCSI device attached to the cable
looks at all the data, but an SCSI device recognizes only the data that has the
proper device identification, called an SCSI ID numbrer.
A.1 SCSI ID Default Settings
You are responsible for the SCSI ID settings on your equipment. Digital sets
each SCSI device to a default setting before the equipment leaves the factory.
You might never need to change a default setting. Default settings should only
be changed when a system is configured with more than one of a particular
device.
The SCSI ID numbers are 0 through 7. The number 7 is reserved for a device
requiring the highest priority on the SCSI bus. The number 6 is reserved for
the controller. The remaining six ID numbers (0 through 5) are available for
custom configuration.
Table A–1 lists the default SCSI settings for the InfoServer 150 system. The
ID numbers listed give optimal performance on most systems. However, if
you have special performance needs, you can set the ID number on each
SCSI device manually. For most applications, SCSI ID numbers can be set
arbitrarily as long as no two devices share the same ID.
A–1