Digital Storage Systems Interconnect: Difference between revisions
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More detail about DSSI; should move SCA stuff to SCA article, and include "CI PPD Architectural Layers" diagram instead |
Substitute diagram showing the relationship between the DSSI and the CI's physical layer, for the SCA diagram |
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DSSI is a 8-bit wide [[parallel]] bus. It is an alternate physical layer in the [[Computer Interconnect]] system; the CI system had a 'native' physical layer before the creation of DSSI. The DSSI specification lists the main attributes of DSSI as: multi-drop linear bus electrical topology; 8-bit parallel; low-cost, [[single-ended signalling]] interface circuitry; [[direct current|DC]] coupling. | DSSI is a 8-bit wide [[parallel]] bus. It is an alternate physical layer in the [[Computer Interconnect]] system; the CI system had a 'native' physical layer before the creation of DSSI. The DSSI specification lists the main attributes of DSSI as: multi-drop linear bus electrical topology; 8-bit parallel; low-cost, [[single-ended signalling]] interface circuitry; [[direct current|DC]] coupling. | ||
The relationship between the DSSI and the CI's physical layer is shown in the following diagram: | |||
<pre> | |||
<-----+ | |||
+---------------------+ | | |||
| Port Driver | | | |||
| Layer | | | |||
| ( SCA Specification)| | | |||
+---------------------+ | | |||
| | | |||
| | | |||
....................... | | |||
. CI Port Adapter . | | |||
. ( eg: VAX CI Port ) . | | |||
....................... | | |||
| | P | |||
+------> | | P | |||
| +---------------------+ | D | |||
| | CI Port | | | |||
C | | Layer | | L | |||
I | | ( DEC Std 161 ) | | A | |||
| +---------------------+ | Y | |||
A | | | | E | |||
R | +------+ +------+ | R | |||
C | | | | | |||
H | +----------------------+ +---------------------+ | | |||
I | | DSSI Datalink | | CI Datalink | | | |||
T | | Layer | .... | Layer | | | |||
E | | ( DSSI Spec. ) | | ( Dec Std 161 ) | | | |||
C | +----------------------+ +---------------------+ | | |||
T | | | <-----+ | |||
U | | | <-----+ P L | |||
R | +----------------------+ +---------------------+ | H A | |||
E | | DSSI Physical | | CI Physical | | Y Y | |||
| | Interconnect | | Interconnect | | S E | |||
| | ( DSSI Spec. ) | | ( DEC Std 161 ) | | I R | |||
| +----------------------+ +---------------------+ | C | |||
+------> <-----+ A | |||
L | |||
Figure 1-2: CI PPD Architectural Layers | |||
</pre> | |||
A description of the DSSI 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 .. that combine a common host interface and port layer with an implementation-specific datalink and physical interconnect. | "The DSSI, supporting the needs of low-end and mid-range systems, is one in a family of high-performance computer-to-computer interconnects .. 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 [[ | CI-class interconnects provide the transmission services required by Digital's [[System Communication Architecture]] (SCA) - a four-tiered set of protocols and interfaces.." | ||
DSSI made it possible to build [[VAXcluster]]s from [[MicroVAX]] and smaller [[VAX]] computers by adding CI-bus functionality to smaller VAX systems. | DSSI thus made it possible to build [[VAXcluster]]s from [[MicroVAX]] and smaller [[VAX]] computers by adding CI-bus functionality to smaller VAX systems. | ||
== DSSI Controllers/Interfaces == | |||
* [[KFQSA]] [[QBUS]] DSSI Adapter | * [[KFQSA]] [[QBUS]] DSSI Adapter | ||
| Line 27: | Line 65: | ||
* [[KFA40]] [[DEC 4000]] I/O Module | * [[KFA40]] [[DEC 4000]] I/O Module | ||
=== | == DSSI Hierarchical Storage Controllers (HSDs) == | ||
[[Hierarchical Storage Controller]]s: | |||
* [[HSD05]] | * [[HSD05]] | ||
| Line 34: | Line 74: | ||
* [[HSD50]] | * [[HSD50]] | ||
== DSSI Disk Drives == | |||
* [[RF30]] | * [[RF30]] | ||
| Line 51: | Line 91: | ||
* [[RF75]] | * [[RF75]] | ||
== DSSI Tape Drives == | |||
* [[TF30]] | * [[TF30]] | ||
Revision as of 01:55, 1 September 2023
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).
DSSI is a 8-bit wide parallel bus. It is an alternate physical layer in the Computer Interconnect system; the CI system had a 'native' physical layer before the creation of DSSI. The DSSI specification lists the main attributes of DSSI as: multi-drop linear bus electrical topology; 8-bit parallel; low-cost, single-ended signalling interface circuitry; DC coupling.
The relationship between the DSSI and the CI's physical layer is shown in the following diagram:
<-----+
+---------------------+ |
| Port Driver | |
| Layer | |
| ( SCA Specification)| |
+---------------------+ |
| |
| |
....................... |
. CI Port Adapter . |
. ( eg: VAX CI Port ) . |
....................... |
| | P
+------> | | P
| +---------------------+ | D
| | CI Port | |
C | | Layer | | L
I | | ( DEC Std 161 ) | | A
| +---------------------+ | Y
A | | | | E
R | +------+ +------+ | R
C | | | |
H | +----------------------+ +---------------------+ |
I | | DSSI Datalink | | CI Datalink | |
T | | Layer | .... | Layer | |
E | | ( DSSI Spec. ) | | ( Dec Std 161 ) | |
C | +----------------------+ +---------------------+ |
T | | | <-----+
U | | | <-----+ P L
R | +----------------------+ +---------------------+ | H A
E | | DSSI Physical | | CI Physical | | Y Y
| | Interconnect | | Interconnect | | S E
| | ( DSSI Spec. ) | | ( DEC Std 161 ) | | I R
| +----------------------+ +---------------------+ | C
+------> <-----+ A
L
Figure 1-2: CI PPD Architectural Layers
A description of the DSSI 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 .. 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 System Communication Architecture (SCA) - a four-tiered set of protocols and interfaces.."
DSSI thus made it possible to build VAXclusters from MicroVAX and smaller VAX computers by adding CI-bus functionality to smaller VAX systems.
DSSI Controllers/Interfaces
- KFQSA QBUS DSSI Adapter
- KFMSA XMI Dual DSSI Adapter
- KFMSB XMI DSSI adapter
- KFESA EISA DSSI Adapter
- KFESB EISA DSSI Adapter
- KFPSA PCI DSSI Adapter
- KFE52 VAXft Multi-Function Interface
- KDXDA VAXft 810 DSSI Interface
- EDA640 MicroVAX 3300/3400 KA640 embedded DSSI Adapter (EDA)
- KFA40 DEC 4000 I/O Module
DSSI Hierarchical Storage Controllers (HSDs)
Hierarchical Storage Controllers:
DSSI Disk Drives
DSSI Tape Drives
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
- RF Series Integrated Storage Element User Guide (EK-RF72D-UG-008)
