Hardware components of the PC
Computer Buses
SCSI bus termination

It is crucial that both ends of the SCSI bus are properly terminated.

Host adapter termination can be detected automatically, require an adapter BIOS setup, or a manual switch setting. The host adapter can be in the middle or at an end of the bus, depending on whether the SCSI devices are internal only, external only, or both internal and external.

Device termination circuitry can be turned on or off in a number of different ways depending on the device. It could be manually changing the position of a switch, moving a jumper setting, or pressing a switch that in turn displays the SCSI ID number. Some SCSI devices have automatic termination, enabling the device to determine whether they are at the end of a bus and turn their built-in termination either on or off.

Either the host adapter or the devices on the ends of the SCSI bus must provide the termination and all other devices along the bus must be set not to provide termination.

The chief advantages of the SCSI:

• Flexible device attachment with up to 7 or 15 hardware devices on a SCSI bus with a host adapter
• Support for almost any peripheral type including hard disks, tapes, CDs, DVD-ROMs, scanners and printers
• SCSI devices share the bus bandwidth efficiently by allowing one device to transfer data while another is seeking or rewinding its media
• Ability to connect both internal and external devices to computer systems
• Large capacity, highest performing devices are usually available in SCSI before other systems.