Make sure you use the right type and length of cable
To attach a SCSI device to your computer or to another device in the chain, always use SCSI cables that are
Avoid mixing brands and types of SCSI cables.
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:
SCSI system cable
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
IMPORTANT The total length of the cables in a SCSI chain should not exceed 6 meters (about 20 feet). SCSI cables must have a
Keep the cables between SCSI devices as short as possible. Cables 18 to 24 inches long are best. PowerBooks and some SCSI devices (particularly scanners) may not be able to handle cables longer than 24 inches.