Apple Power Macintosh 4400 - Manual (Page 49)

You can connect several SCSI devices to the SCSI port by linking them
together in a chain: the first device in the chain plugs into the SCSI port; the
second device plugs into the first device, and so on. You can attach up to
seven external SCSI devices to the SCSI port.
Each SCSI device connected to this chain must have its own unique ID
number (no two devices can use the same ID number). The computer itself
(the main logic board inside it) uses SCSI ID number 7.
IMPORTANT The material that follows—“Before You Connect a Device” and
“Connecting a SCSI Device”—contains general instructions for attaching SCSI
devices to your computer. Make sure you also follow the specific instructions
that came with the SCSI device you are connecting to your Macintosh.
Before you connect a 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 the device.
Make sure each device has a unique ID
Each 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.
Make sure other SCSI devices you add to the chain do not use ID numbers
that are already assigned. 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 equipment could malfunction and
you could lose data as a result.
49 Connecting Equipment and Expanding Your Computer