Apple Power Macintosh 7600/120 Series - Manual (Page 66)

Before you connect a device
Before you connect a SCSI device to your Macintosh, be sure to complete
these tasks:
m Make sure each SCSI device connected to your Macintosh has its own,
unique ID number from 0 to 6 (or from 1 to 6 if you have a second internal
hard disk installed). 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.
m Make sure you have the appropriate cable for attaching the SCSI device to
your Macintosh.
If the device is the first or only one you’re connecting, use a SCSI system
cable to connect it to the computer’s SCSI port:
If the device is not the first one, use a SCSI peripheral interface cable to
connect it to the last device in the chain:
SCSI peripheral interface cable
SCSI system cable
55 Connecting Additional Equipment