Scsi Cable And Scsi Termination; General Procedure For Installing Scsi Devices; Figure 9-11. Internal Scsi Cables - Dell Precision 400 User Manual

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A SCSI CD-ROM drive is configured as SCSI ID 5.
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SCSI hard-disk drives are usually configured as
SCSI ID 0. (The drive used to boot your system
should always be configured as SCSI ID 0.)
NOTE: There is no requirement that SCSI ID numbers be
assigned sequentially or that devices be attached to the
cable in order by ID number.

SCSI Cable and SCSI Termination

The type of cabling you receive with your SCSI device
depends on the type of device you are installing.
If you are installing an internal narrow SCSI device (such
as a CD-ROM drive or tape drive), you have a 50-pin
internal SCSI cable as shown in Figure 9-11. One end of
this cable attaches to the SCSI host adapter. The other
two connectors on the other end of the cable attach to up
to two narrow SCSI devices installed in the externally
accessible drive bays. The middle connection on the
cable is not used.
68-pin SCSI cable

Figure 9-11. Internal SCSI Cables

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If you are installing an internal wide SCSI device
(such as a wide SCSI hard-disk drive), you have a
68-pin internal SCSI cable as shown in Figure 9-11.
One end of this cable attaches to the SCSI host
adapter and the other two connectors attach to up to
two SCSI hard-disk drives installed in the hard-disk
drive bracket.
9-12 Dell Workstation Midsize Systems User's Guide
50-pin SCSI cable
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If you are installing an external SCSI device, you
have a shielded external cable that connects to the
external SCSI connector on the SCSI host adapter
card. You have a separate power cable to connect the
SCSI device to an AC power source.
Before installing SCSI devices in your computer, you
may need to configure the termination on your SCSI
devices. Both types of internal SCSI cables contain ter-
minators on the device end of the cables, so the devices
connected to these cables must have termination
disabled. External SCSI cables do not have terminators,
so termination must be enabled on the SCSI device itself.
If you are installing only internal SCSI devices, verify
that termination is enabled on the SCSI host adapter and
disabled for all other internal SCSI devices. If you are
installing both internal and external SCSI devices, verify
that termination is enabled on the external SCSI device
and disabled for the SCSI host adapter and all internal
SCSI devices.
CAUTION: Do not connect devices to all three con-
nectors (internal narrow connector, internal wide
connector, and external connector) on a single SCSI
host adapter card. Such a configuration is a viola-
tion of the SCSI specification. You can safely
connect devices to any two of these three connectors
on a single SCSI host adapter card.
General Procedure for Installing SCSI
Devices
Configure and install one or more SCSI devices in your
computer as follows:
1. Determine which connector on the internal SCSI
cable you will attach to each SCSI device.
See "SCSI Configuration Guidelines" found earlier
in this section.
2. Unpack each SCSI device and prepare it for
installation.
Ground yourself by touching an unpainted metal sur-
face on the back of the computer. Configure the
device for a SCSI ID number and termination, if nec-
essary. For instructions, see the documentation that
came with the SCSI device as well as "SCSI Config-
uration Guidelines" found earlier in this section.