Connecting The Device; Connecting An External Scsi Device - Power Computing PowerTower Pro User Manual

Chapter 2, Connecting Peripheral Devices

Connecting the device

Connecting an external SCSI device

The SCSI port, marked with
computer and devices such as hard disks, CD-ROM drives, scanners, printers, tape backup
drives, and so on.
To connect a single SCSI device (or the Þrst device in a chain), you need a SCSI cable with
a 25-pin connector on one end and a 50-pin connector on the other. For each additional
external device, you need a cable with 50-pin connectors on both ends. The cables you use
should be double-shielded and have approximately 110-ohm impedance. Most SCSI
problems are the result of low-grade cables. Of the SCSI cables our engineers have tested,
Apple and APS cables are recommended for consistent reliability. We also recommend
using active termination on external chains to minimize termination problems.
Note: External SCSI devices which are connected to the computer have independent power
systems and must be turned on and off at the device; internal SCSI devices are powered by
the computer and turn on and off when the computer does. Devices on the SCSI bus which
are turned off can cause system errors.
To connect an external SCSI device:
1.
Shut down the computer and the SCSI device.
2.
Make sure that the device has a unique SCSI ID from 0 to 6.
For details, see ÒSetting the SCSI IDÓ on page 16.
3.
Connect the device to the computerÕs SCSI port or to the last device in the
chain, using the appropriate cable.
4.
Make sure that the last device in the chain is terminated.
Some devices require an external terminator, while others are internally terminated.
When you are ready to start up, turn on your SCSI devices before you turn on the computer.
If you do not, your computer will not recognize the devices.
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PowerTower Pro UserÕs Guide
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, provides 5 MB per second communication between the
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