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PCA-6185 User’s Manual 70
7.4 Terminating the SCSI bus
To ensure reliable communication on the SCSI bus, the ends of the SCSI
bus must be properly terminated. This is accomplished when the device at
the end of the each cable, or the end of the cable itself, has a terminator
installed (or enabled). Terminators must be removed, or termination must
be disabled, on devices between the ends of each cable.
Since the method for terminating a SCSI device can vary widely, refer to
the device’s documentation for instructions on how to enable or disable
termination. Here are some general guidelines for termination:
• Internal Ultra 320 and Ultra 2 SCSI devices come from the factory with
termination disabled and cannot be changed. Proper termination for
internal Ultra 320 and Ultra2 SCSI devices is provided by a 68-pin
Internal LVD (low voltage differential) SCSI cable, which has a built-
in terminator at its end.
• Termination on non-Ultra 320 and Ultra2 internal SCSI devices usually
is controlled by manually setting a jumper or a switch on the device, or
by physically removing or installing one or more resistor modules on
the device.
• Termination on most external SCSI devices is controlled by installing
or removing a SCSI terminator. However, termination on some exter-
nal SCSI devices is enable or disabled by setting a swetich on the back
of the SCSI device.
• The last external Ultra 320 or Ultra2 SCSI device must be terminated
with an LVD/SE (low voltage differential/single ended) terminator
plug to ensure that the device will operate at its maximum speed. If you
use a different kind of terminator plug, the data I/O rate will decrease.
By default, termination on the SCSI controller itself is set to Automatic
(the preferred method). We recommend that you do not change this
default setting.
7.5 Configuring the SCSI interface with SCSISelect
SCSISelect, included with the CPU card, enables you to change SCSI set-
tings without opening the computer. SCSISelect also enables you to low-
level format or verify the disk media of your SCSI hard disk drives. The
following table lists the available and default settings for each SCSISelect
option.
Note: The default settings are appropriate for most sys-