View source for VAX 85xx, 87xx, and 88xx systems

The '''VAX 85xx, 87xx, and 88xx systems''' are a range of uni-processor and [[multi-processor]] [[supermini]] [[VAX]] systems that share being built around the [[NMI Memory Interconnect]] [[bus]] (probably the 'Nautilus Memory Interconnect', although no remaining [[DEC]] documentation gives the expansion of 'NMI'). The [[Central Processing Unit|CPUs]], [[main memory]] and [[input/output|I/O]] adapters (called 'NBIs') all connect to the NMI; 8800 family systems use the [[VAX Bus Interconnect|VAXBI]] [[bus]] for their I/O bus(es).

The 8800 family uses [[emitter-coupled logic|ECL]] [[gate array]]s throughout, organized in [[synchronous]] logic. (In dual-CPU systems, the two CPUs run off a common [[clock]].)

Although given three different model designations - VAX 85xx, VAX 8700, and VAX 8800 - the DEC internal superordinate name was "VAX 8800 Family" from the beginning:

''"The VAX 8800 multiprocessor and the VAX 8700, 8550, and 8500 systems all derive from the same fundamental design. Their sustained applications throughput ranges from 3.0 to 12 times that of the VAX-11/780 system. In the design process, automated tools helped to correct design bugs early. ECL technology and a two-phase clock system achieve a 45-nanosecond cycle time. [[Microcode|Micro instructions]] are processed simultaneously through four logic boxes that implement a five-stage [[pipeline]]. A high-speed memory interconnect, the NMI bus, links CPUs to memory and the I/O subsystem, which connects to VAXBI buses. Many reliability features, including extensive diagnostics, are implemented."'' [[#ref_1|[1]]]

== Two Generations of VAX 8800 Family models ==

There are two generations of VAX 8800 Family models:

* First generation models (1985/86): [[VAX 8500/VAX 8530| VAX 8500]], [[VAX 8500/VAX 8530| VAX 8530]], [[VAX 8550]], [[VAX 8700]], [[VAX 8800]]
* Second generation models (1987/88): [[VAX 8810]], [[VAX 8820]], [[VAX 8830]], [[VAX 8840]]

While the first-generation VAX 8700 and VAX 8800 systems supported [[Asymmetric Multiprocessing]] (ASMP) for dual CPUs, the second-generation models introduced [[Symmetric Multiprocessing]] (SMP) with up to four processors in conjunction with [[VMS]] V5.0.

Both generations employed a dedicated computer for console operations; the first-generation models used a special version of the [[PDP-11]]-based [[Professional 300 Series|Professional 380]], the second-generation ones a [[MicroVAX II]]. 

== VAX 8800 Family Commonalities ==

There are a couple of commonalities:

* "Box Design" (first introduced with the [[VAX 8600]])
* Common Basic CPU Boards
* [[MS88]] Memory Modules
* Microcode Format
* System Busses

=== Box Design ===

* N Box = Power Conditioning Box 
* E Box = Execution Box
* C Box = Cache Box
* M Box = Memory Box
* I Box = Instruction Box

=== Common Boards ===

CPU Boards common to all of the VAX 8800 Family models:

* F1002 Shifter Module
* F1003 ALU Slice 1
* F1004 ALU Slice 0
* F1005 Address Data Path
* F1009 Writable Control Store Module
* F1011 DB88 NMI to BI Interface Module
* F1021 Memory Controller

=== MS88 Memory Modules ===

All VAX 8800 Family models share the MS88 memory modules:

* MS88-AA  4MB
* MS88-CA 16MB
* MS88-DA 64MB

=== Buses ===

All VAX 8800 Family models share the same set of buses:

* Data-Path Buses
* NMI = Memory Interconnect Bus
* [[VBUS]] = Visibility Bus - a slow-speed bus used for [[diagnostic]]s and initialization
* VAXBI = Backplane Interconnect Bus

== Comparison of VAX 8800 Family models ==

{| class="wikitable" style="margin:auto;text-align: center"
|+ VAX 8800 Family Model Overview
|-
! !!colspan="5"|First Generation !! colspan="4"|Second Generation
|-
! !! VAX 8500 || VAX 8530 || VAX 8550 || VAX 8700 <br> VAX 8810N || VAX 8800 <br> VAX 8820N || VAX 8810 || VAX 8820 || VAX 8830 || VAX 8840
|-
!Nickname !! colspan="2"|Flounder || Skipjack || colspan="2"|Nautilus || colspan="4"|Polarstar
|-
| CPU Name || colspan="2"| 851BA || 855BA || 871BA || 882BA || colspan="4"| 885BA
|-
| # of CPUs || 1 || 1 || 1 || 1 || 2 || 1 || 2 || 3 || 4 
|-
| Upgradable to || VAX 8530 || VAX 8550 || None || VAX 8800 || None || VAX 8820 || VAX 8830 || VAX 8840 || None
|-
| Type of MP || colspan="3"| - || colspan="2"| ASMP || colspan="4"| SMP  
|-
| ECL MCA || colspan="9"| 45ns
|-
| VUPS || 3.2 || 4.2 || 6.5 || 6.5 || 11.4 || 6.5 || 11.4 || 16.8 || 22.2
|-
| max. # of BI buses || colspan="3"| 2 || colspan="2"| 4 || colspan="4"| 6
|-
| max. # of Memory modules || colspan="3"| 5 || colspan="6"| 8  
|-
| Console || colspan="5"| Professional 380 || colspan="5"| MicroVAX II
|-
| min. VMS version || V4.4 || V4.6 || colspan="3"| V4.4 || colspan="5"| V5.0 
|}

== Model Differences ==

=== VAX 8500 <=> VAX 8530 ===
 
The VAX 8530 is a VAX 8500 with "optimized" Microcode. There is a rumor that the optimization was to remove [[NOP]]s from the [[Microcode]], but that hasn't bee confirmed yet.

=== VAX 8500/8530 <=> VAX 8550 ===

The only difference between a VAX 8500/8530 and a VAX 8550 is a different Instruction Decode Module '''F1007''', the VAX 8500/8530 module was the '''F1015''' (see also: [[DEC Modules by bus]]).

=== VAX 8550 <=> VAX 8700/8800 ===

* All VAX 85xx models and the VAX 8700 are single CPU computers, but the VAX 8700 is expandable with a second CPU, which results in a VAX 8800 model.
* All VAX 85xx models have somewhat limited expansion possibilities in comparison to the VAX 8700 / VAX 8800 models:
** A maximum of 5 memory modules with the VAX 85xx; 8 memory modules maximum with the VAX 8700/8800.
** A maximum of 2 BI buses with the VAX 85xx; 4 BI buses maximum with the VAX 8700/8800, and 6 BI buses maximum with the VAX 88x0 models.

== VAX 8974, VAX 8978, and VAX 8842 Prepackaged Cluster Systems ==

There were three different prepackaged [[VAXcluster]] systems built from VAX 8700/VAX 88xx systems:

* [[VAX 8974/VAX 8978 | VAX 8974]] - A VAXcluster of four VAX 8700 (later: VAX 8810)
* [[VAX 8974/VAX 8978 | VAX 8978]] - A VAXcluster of eight VAX 8700 (later: VAX 8810)
* [[VAX 8842]] - A VAXcluster of two VAX 8820 (upgrade to VAX 8830s / VAX 8840s possible)

All three came complete with cluster hardware, storage devices, and software.
 
Both the VAX 8974 as well as the VAX 8978 were based on the VAX 8700 until the VAX 8810 came out in 1987, which then replaced the VAX 8700s in both the VAX 8974 and the VAX 8978.

It is not known how many VAX 8974 and VAX 8978 VAXcluster systems were ever build and sold.

There is an interesting article on benchmarks performed on the VAX 8974 and VAX 8978:<br> ''System Level Performance of VAX 8974 and 8978 Systems'', in [https://vmssoftware.com/docs/dtj-v01-05-sep1987.pdf [[Digital Technical Journal|DTJ]], Vol. 1 No. 5], September, 1987 (pp. 82-94 of the PDF)

You can watch a video about a VAX 8974 VAXcluster system being build up on YouTube: [https://www.youtube.com/watch?v=gFb0Dw10YUo Digital Equipment - New York VAX 8974 Cluster Install - Jul 1987]

== References ==

 <div id="ref_1">[1] "VAX 8800 Family", Digital Technical Journal, Vol 1 No 4, February 1987. </div>
 <div id="ref_2">[2] VAX Hardware Handbook. Volume 2-1986. </div>

==Further reading==

* [http://www.dtjcd.vmsresource.org.uk/pdfs/dtj_v01-04_feb1987.pdf VAX 8800 Family], [[Digital Technical Journal]], No. 4 - the entire issue is devoted to the 8800 family

==External links==

* [http://www.bitsavers.org/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_2_1986.pdf VAX Hardware Handbook Volume 2] - the VAX 8800 is covered in Chapter 2 (pp. 24-49 of the PDF)
* [http://www.bitsavers.org/pdf/dec/vax/8800/ 8800] - VAX 88xx documentation at [[Bitsavers]]
** [http://www.bitsavers.org/pdf/dec/vax/8800/EK-8840H-UG-001_88xx_System_Hardware_Users_Guide_Mar88.pdf VAX 8820/8830/8840 System Hardware User's Guide] (EK-8840H-UG-001)
** [http://www.bitsavers.org/pdf/dec/vax/8800/EK-KA881_8800sysTech1_Jul86.pdf VAX 8800 System Technical Description - Volume 1] (EK-KA881-TD-PRE) - Introduction and overview; system buses; console subsystem; power system; clock
** [http://www.bitsavers.org/pdf/dec/vax/8800/EK-KA882_8800sysTech2_Jul86.pdf VAX 8800 System Technical Description - Volume 2] (EK-KA882-TD-PRE) - IBox; EBox; CBox
** [http://www.bitsavers.org/pdf/dec/vax/8800/EK-KA883_8800sysTech3_Jul86.pdf VAX 8800 System Technical Description - Volume 3] (EK-KA883-TD-PRE) - MBox; NBI

* [https://techmonitor.ai/technology/top_end_dec_vax_8974_8978_are_stop_gaps_to_true_mp_vms Top-End DEC VAX 8974, 8978 are Stop-Gaps to True MP VMS]

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[[Category: VAX Families]]
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[[Category: VAX 85xx/87xx/88xx Systems]]