Apple Power Macintosh 9600 - Manual (Page 85)

Before you connect a SCSI device
Before you connect a SCSI device to your Macintosh, be sure to complete the
tasks explained in this section.
IMPORTANT This section contains general instructions for attaching SCSI
devices to your computer. Be sure also to follow the specific instructions that
came with your external hard disk drive or other SCSI device when
connecting the device to your Macintosh. The specific instructions that came
with the device tell how to change a device’s ID number and attach a SCSI
cable or terminator to it.
Make sure each device has a unique ID number
Each external SCSI device connected to your computer must have its own,
unique ID number from 0 to 6. The SCSI ID number helps the computer keep
track of the devices and sort out conflicts when more than one device in the
SCSI chain is communicating with the computer simultaneously.
The SCSI devices can be in any physical order in the chain; it is not necessary
to arrange them in numerical order.
See the instructions that came with each SCSI device for information on
checking and setting its SCSI ID number.
IMPORTANT If you use two or more devices attached to the same SCSI
interface with the same ID number, your computer will not start up properly,
your equipment could malfunction, and you could lose data as a result.
85 Connecting Additional Equipment