Scsi Configuration Guidelines; Scsi Id Numbers; Device Termination - Dell 6100 Service Manual

detailed information about installing SCSI hard-disk drives, see Chapter 10, "Install-
ing Drives in the Internal Bays," in the Installation and Troubleshooting Guide.
Dell supports only the drives it furnishes.

SCSI Configuration Guidelines

Although SCSI devices are installed essentially the same way as other devices,
their configuration requirements are different. To configure your SCSI sub-
system, follow the general guidelines offered in the following subsections.

SCSI ID Numbers

For SCSI devices in the external drive bays, each device attached to the 7880
Ultra/Wide SCSI host adapter must have a unique SCSI ID number from 0 to 7.
For additional SCSI addressing information, see Chapter 9, "Installing Drives in
the External Bays," in the Installation and Troubleshooting Guide.
When SCSI devices are shipped from Dell, the default SCSI ID numbers are
assigned as follows:
•
The computer's built-in Ultra/Wide SCSI host adapter is configured through
the BIOS as SCSI ID 7.
•
A SCSI CD-ROM drive is configured as SCSI ID 5 (configured as the last
device).
•
A SCSI tape drive (if installed) is configured as SCSI ID 6.
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.
For the SCSI devices in the internal drive bays, devices attached to the
Ultra/Wide SCSI host adapter need no ID settings or termination; ID settings
and termination are handled automatically by the SCSI backplane.

Device Termination

SCSI logic requires that termination be enabled for the two devices at opposite
ends of the SCSI chain and disabled for all devices in between. Therefore,
regardless of whether you are installing internal or external devices, use the fol-
lowing guidelines:
•
A single SCSI device (such as the standard CD-ROM drive) is terminated.
•
If two or more SCSI devices are installed, connect the devices as follows:
Attach one of the devices to the end connector on the SCSI cable, and
—
leave the terminator enabled on that device.
The other end of the SCSI cable, which has built-in termination, connects
—
to the computer's built-in SCSI host adapter or to an optional SCSI host
adapter card.
Disable the terminators on all other devices you attach to the cable.
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