A device that cross connects computers to SCSI devices and overcomes certain SCSI limitations. The regular SCSI interface is a shared bus architecture, but a SCSI switch provides the full bandwidth between any two devices, greatly increasing overall throughput. This is the same concept as shared Ethernet versus an Ethernet switch.
SCSI switches also double the cable distance between devices and minimize access contention, because the devices are not subject to a priority by their ID numbers. In addition, the 7-device or 15-device limit gives way to any number of devices, because the switches can be cascaded. See SCSI
Shared Vs. Switched
Switched SCSI eliminates many limitations, including bandwidth, cable distance and number of devices. The switch has a backplane capable of handling the full SCSI bandwidth at each of its ports.
Extending the Limitations
GigaLabs pioneered the SCSI switch, but later went out of business. This JigSaw 8-slot model provided 16 non-blocking ports between SCSI devices. (Image courtesy of GigaLabs, Inc.)