• Small Computer System Interface
• Designed to be implemented in hardware
• SCSI Controller performs controller functions
– These functions performed by host CPU on Parallel ATA/Serial ATA drives
• Confusing descriptors – “Fast”, “Wide”, “Ultra”
• attach up to 8 devices on a Fast bus
• attach up to 16 devices on a Wide bus
• Half duplex – only operates in one direction at a time
• Interface transfer rate
– Ultra3 SCSI, transfer rates of 160 MB/s
– Ultra320 SCSI available, transfer rates of 320 MB/s
• Supports SCSI protocol & command set
Parallel SCSI was originally developed with performance as its primary
concern so implemented an architecture that uses a hardware controller to
control the drive functions. SCSI is always implemented in hardware.
It operated up to a burst rate of 320MB/s, and would support up to sixteen
devices on a wide bus configuration.
SCSI addresses at the sector level using a Logical Block Address and it
supports command queuing to optimise seek times.
SCSI Command Tag Queuing.