View source for Digital Storage Systems Interconnect

The '''Digital Storage Systems Interconnect''' (usually given as '''DSSI''') is a [[mass storage]] [[bus]] from [[Digital Equipment Corporation|DEC]]. It can also be used to create loosely-coupled [[multi-processor]]s by sharing a number of [[disk drive]]s between two systems. Such shared drives are termed 'Integrated Storage Elements' (ISEs).

DSSI made it possible to build [[VAXcluster]]s from [[MicroVAX]] and smaller [[VAX]] computers by adding CI-bus functionality to smaller VAX systems.

[[File:The SCA Model.png|thumb|right|350px|Systems Communication Architecture]]

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 ([[Computer Interconnect|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]] [[Central Processing Unit|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.

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==External Links==

* [http://bitsavers.org/pdf/dec/dsa/dssi/ DSSI] - DSSI and related documents at [[Bitsavers]]
** [http://www.bitsavers.org/pdf/dec/dsa/dssi/Digitals_Storage_System_Interconnect_Rev_1.0.0_199003.txt Digital's Storage System Interconnect] - protocol specification document
* [http://www.bitsavers.org/pdf/dec/vax/3800/EK-338AC-DH-003_MicroVAX_Dual-Host_Systems_Dec90.pdf 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

[[Category: DEC Buses]]
[[Category: DEC Mass Storage]]
[[Category: DSSI]]