Dell Mini Tower System manual Scsi Configuration Guidelines, Scsi ID Numbers

Although SCSI devices are installed essentially the same way as other devices, their configuration requirements are different.

SCSI Configuration Guidelines

For details on configuring your SCSI subsystem, refer to the documentation that came with your SCSI devices and/or your host adapter card. The following subsections offer some general guidelines.

SCSI ID Numbers

Each device attached to a SCSI host adapter card, as well as the card itself, must have a unique SCSI identification (ID) number from 0 to 7. When SCSI devices are shipped from Dell, the default SCSI ID numbers are assigned as follows:

•A SCSI host adapter card is configured as SCSI ID 7.

•A SCSI tape drive or digital audio tape (DAT) drive is configured as SCSI ID 6.

•A SCSI CD-ROM drive is configured as SCSI ID 5.

•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 7-14. One end of this cable attaches to the SCSI host adapter. The three connectors on the other end of the cable are used for attaching up to three narrow SCSI devices installed in the externally accessible drive bays.

50-pin SCSI cable (to device in externally accessible drive bay)

68-pin SCSI cable (to hard-disk drive)

Figure 7-14. Internal SCSI Cable

•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 7-14. One end of this cable attaches to the SCSI host adapter and the two connectors on the other end of the cable are used for attaching up to two SCSI hard- disk drives installed in the hard-disk drive bracket.

•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 device(s). 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 dis- abled. 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 dis- abled for all other internal SCSI devices. If you are installing both internal and external SCSI devices, verify that termina-

Installing Drives 7-11