Digital Storage Systems Interconnect
The Digital Storage Systems Interconnect (usually given as DSSI) is a mass storage bus from DEC. It can also be used to create loosely-coupled multi-processors by sharing a number of disk drives between two systems. Such shared drives are termed 'Integrated Storage Elements' (ISEs).
Description from the 'Digital's Storage System Interconnect' protocol specification document:
"The DSSI, supporting the needs of low-end and mid-range systems, is one in a family of high-performance computer-to-computer interconnects (CI's) that combine a common host interface and port layer with an implementation-specific datalink and physical interconnect.
CI-class interconnects provide the transmission services required by Digital's Systems Communication Architecture (SCA) - a four-tiered set of protocols and interfaces as shown [to the right]."
The QBUS DSSI peripheral was the KFQSA. Some VAX CPU's had built-in DSSI peripherals, called 'Embedded DSSI Adapters' (EDAs); one such was the KA640 CPU of the MicroVAX 3300/3400. The VAX 4000 series also supported the DSSI.
External Links
- DSSI - DSSI and related documents at Bitsavers
- Digital's Storage System Interconnect - protocol specification document
- MicroVAX Dual-Host Systems (EK-338AC-DH-003) - contains a clear description of how a DSSI can be used to create a loosely-couple multi-processor
