Installing Optional Scsi Devices; Important Guidelines For Installing Optional Scsi Devices - Compaq Deskpro AP550 Maintenance And Service Manual

3-18 Compaq Professional Workstation AP550 Maintenance and Service Guide

Installing Optional SCSI Devices

Select models of the Compaq Professional Workstation AP550 have a preinstalled internal SCSI
hard drive. You can install additional SCSI devices using the external SCSI connector located
on the rear panel of the workstation.

Important Guidelines for Installing Optional SCSI Devices

If you are installing additional SCSI devices, you MUST adhere to the following guidelines:
A narrow SCSI controller allows you to daisy-chain up
to seven additional SCSI devices.
A single Ultra SCSI, Ultra-Wide SCSI, or Wide-Ultra
SCSI controller allows you to daisy-chain up to 15
additional SCSI devices.
The SCSI controller requires a unique SCSI ID (0-7 or
8-15) for each SCSI device installed. The controller
identifies a SCSI device by its SCSI ID number rather
than its location.
SCSI ID 0 is reserved for the primary hard drive.
SCSI ID 7 is reserved for the controller.
If only one SCSI hard drive is used, install it in the
lowest-numbered bay (bay 1).
Every SCSI chain or circuit must be terminated
(closed) at both ends. Termination can be
accomplished in one of several ways:
Use a cable with a built-in terminator.
Use a cable with a terminating resistor plug in
the last connector.
Connect a SCSI device with its termination
enabled into the last connector.
Connect an external SCSI device with its
termination enabled to the external SCSI
connector on the rear panel of the computer.
Table 3-2
Installing Optional SCSI Devices
Guidelines Comment
Counting the controller, that amounts to eight total
SCSI devices
Counting the controller, that amounts to 16 total SCSI
devices.
Moving a SCSI device from one position to another on
the SCSI chain does not affect communication
between the controller and the device.
SCSI IDs 1 through 6 and 8 through 15 are available
for all other SCSO devices.
Some system boards have both ends of the SCSI
cable connected to, and terminated by, the system
board.
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