I/O Interfaces
Parallel SCSI
SCSI-2
Enhanced SCSI Command set
Open Parallel
Bus Structure
Fast
Wide
Data/Address Bus
SCSI
Initiator
Differential
(Host Bus
Adaptor)
Control Signals
Interface Interface
SCSI Disk Drive SCSI Disk Drive
Correct termination is
essential
Fast SCSI moves the data at double the clock rate.
Wide SCSI carries two Bytes at a time on wide cable and was introduced for
greater speed and more device address capability.
Fast and Wide SCSI can be used together.
Differential SCSI used different signalling voltage levels to allow SCSI busses
to go further distance.
Fast, Wide and Differential SCSI can be used together.
SCSI-2 has a series of ‘enhanced’ SCSI commands which extend the
functionality of SCSI over SCSI-1. The common command set resides in the
system software and is utilised by the SCSI driver supported by the SCSI
adapter card.