VAX

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This article is about the computing term VAX, not to be confused with the vacuum cleaner/floorcare manufacturer Vax (vacuum).
DEC VAX
Manufacturer: Digital Equipment Corporation
Byte size: 8 bits (octet)
Address bus size: 32 bits
Peripheral bus: Unibus, Massbus, Q-Bus
Architecture: CISC, virtual memory
Operating systems: VAX/VMS, Ultrix, BSD UNIX

VAX is a 32-bit computing architecture that supports an orthogonal instruction set (machine language) and virtual addressing (i.e. demand paged virtual memory). It was developed in the mid-1970s by Digital Equipment Corporation (DEC). DEC was later purchased by Compaq, which in turn was purchased by Hewlett-Packard.

The VAX has been perceived as the quintessential CISC processing architecture, with its very large number of addressing modes and machine instructions, including instructions for such complex operations as queue insertion/deletion and polynomial evaluation.

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[edit] The name

"VAX" was originally an acronym for Virtual Address eXtension, both because the VAX was seen as a 32-bit extension of the older 16-bit PDP-11 and because it was a commercial pioneer in using virtual memory to manage this larger address space. Early versions of the VAX processor implemented a "compatibility mode" that emulated many of the PDP-11's instructions, and were in fact called VAX-11 to highlight this compatibility and the fact that VAX-11 was an outgrowth of the PDP-11 family. Later versions offloaded the compatibility mode and some of the less used CISC instructions to emulation in the operating system software.

VAX is also a brand of wet-dry vacuum cleaners, invented in the 1970s by Mick Atkinson. There are varied accounts of the legal interactions between DEC and the VAX corporation over the use of this trademark. The terms of the settlement involved a non-competition agreement between the companies—DEC would not move into household appliances and the VAX corporation would stay out of computing. In the historical context, when many industrial electronics firms were involved in development of large computer systems, this seemed much less ridiculous than today.

The advertising slogan of a rival vacuum cleaner manufacturer, Electrolux, was humorously punned on by users of VAX computers to the slogan "Nothing sucks like a Vax".

Among users of the system, VAXen is usually used as the plural of VAX computer system.

[edit] Operating systems

The "native" VAX operating system is DEC's VAX/VMS (later renamed OpenVMS, See "OpenVMS User's Guide", by Patrick J. Holmay). The VAX architecture and VMS operating system were "engineered concurrently" to take maximum advantage of each other, as was the initial implementation of the VAXcluster facility. Other VAX operating systems have included various releases of BSD UNIX up to 4.3BSD, Ultrix-32 and VAXeln. More recently, NetBSD and OpenBSD support various VAX models and some work has been done on porting Linux to the VAX architecture.

VAX-11/780
VAX-11/780

[edit] History

The first VAX model sold was the VAX-11/780, which was introduced on October 25, 1977 at the Digital Equipment Corporation's Annual Meeting of Shareholders[1]. The architect of this model was Bill Strecker. Many different models with different prices, performance levels, and capacities were subsequently created. VAX superminis were very popular in the early 1980s.

For a while the VAX-11/780 was used as a baseline in CPU benchmarks because its speed was about one MIPS. Ironically enough, though, the actual number of instructions executed in 1 second was about 500,000. One VAX MIPS was the speed of a VAX-11/780; a computer performing at 27 VAX MIPS would run the same program roughly 27 times faster than the VAX-11/780. Within the Digital community the term VUP (VAX Unit of Performance) was the more common term, because MIPS do not compare well across different architectures. The related term cluster VUPs was informally used to describe the aggregate performance of a VAXcluster. The performance of the VAX-11/780 still serves as the baseline metric in the BRL-CAD Benchmark, a performance analysis suite included in the BRL-CAD solid modeling software distribution.

The VAX went through many different implementations. The original VAX was implemented in TTL and filled more than one rack for a single CPU. CPU implementations that consisted of multiple ECL gate array or macrocell array chips included the 8600, 8800 superminis and finally the 9000 mainframe class machines. CPU implementations that consisted of multiple MOSFET custom chips included the 8100 and 8200 class machines.

The MicroVAX-I represented a major transition within the VAX family. At the time of its design, it was not yet possible to implement the full VAX architecture as a single VLSI chip (or even a few VLSI chips as was later done with the VAX 8200/8300). Instead, the MicroVAX-I was the first VAX implementation to move most of the complexity of the VAX instruction set into emulation software, preserving just the core instructons in hardware. This new partitioning substantially reduced the amount of microcode required and was referred to as the "MicroVAX" architecture. In the MicroVAX-I, the ALU and registers were implemented as a single gate-array chip while the rest of the machine control was conventional logic.

A full VLSI (microprocessor) implementation of the MicroVAX architecture then arrived with the MicroVAX-II's 78032 chip. This was followed by CVAX, SOC ("System On Chip", a single-chip CVAX), Rigel, Mariah and NVAX chips. The VAX microprocessors extended the architecture to inexpensive workstations and later also supplanted the high-end VAX models. This wide range of platforms (mainframe to workstation) using one architecture was unique in the computer industry at that time.

The VAX architecture was finally superseded by RISC technology. In 1989 DEC introduced a range of workstations based on processors from MIPS Technologies and running Ultrix. In 1992 DEC introduced their own RISC processor, the Alpha (originally named Alpha AXP), a high performance 64-bit RISC architecture capable of running OpenVMS.

In August 2000, Compaq announced that the remaining VAX models would be discontinued by the end of the year[2]. By 2005 all manufacturing of VAX computers had ceased, but old systems remained in widespread use.

The SRI CHARON-VAX and SIMH software-based VAX emulators remain available.

[edit] Trivia

The phrase, "CVAX — when you care enough to steal the very best" ("СВАКС... Когда вы забатите довольно воровать настоящий лучший", a play on the well-known Hallmark Cards slogan[3]) was written in poor Russian on the Digital CVAX microprocessor used in the MicroVAX 3000 and 6200 [4]. It was intended to send a special message to Soviet engineers attempting to reverse engineer DEC's chip design.

[edit] VAX models

Listed in roughly chronological order. The codenames used during development within Digital Equipment Corporation are shown in italic. VAX systems can be broadly classified into those with non-VLSI processors and those with VLSI processors with the MicroVAX-I being a transitional design:

[edit] Non-VLSI VAXen

  • VAX 11/780 (Star, TTL CPU, October 1977[1])
  • VAX 11/750 (Comet, More-compact, lower-performance TTL gate array-based implementation, October 1980)
  • VAX 11/751 (ruggedized rack-mount 11/750)
  • VAX 11/730 (Nebula, Still-more-compact, still-lower-performance bit slice implementation, April 1982)
  • VAX 11/782 (Atlas, Dual-processor 11/780)
  • VAX 11/784 (VAXimus, Four 11/780 CPUs sharing a single MA780 memory unit. Very rare)
  • VAX 11/785 (Superstar, Faster 11/780, April 1984)
  • VAX 11/787 (dual processor 11/785)
  • VAX 11/788 (VISQ)
  • VAX 11/725 (LCN, Low-Cost Nebula)
  • VAX 8600    (Venus, aka 11/790 during development, ECL gate array CPU, October 1984)
  • VAX 8650    (Morningstar, aka 11/795 during development, a faster 8600, last model to use SBI backplane also used by VAX 11/78x models, last model to have PDP-11 compatibility mode. All subsequent 8000 series models use VAXBI instead of SBI)
  • VAX 8x00    (Gemini, Fall-back in case the LSI-based Scorpio failed; Never shipped)
  • VAX 8500    (Flounder, Single-processor, deliberately-slowed VAX 8700)
  • VAX 8530    (Skipjack, Single-processor, less-slowed VAX 8700)
  • VAX 8550    (Skipjack, Single-processor 8800, unexpandable)
  • VAX 8700    (Nautilus, Single-processor Nautilus, expandable to full 8800)
  • VAX 8800    (Nautilus, Dual-processor ECL Macrocell array-based implementation, January 1986; Later variously known as VAX 8820N)
  • VAX 8810/8820/8830/8840 (Polarstar, a Nautilus variant with one to four processors and an updated console processor)
  • VAX 8974/8978 (cluster comprising four or eight VAX 8810s respectively, January 1987)
  • VAX 9000    (Aridus, Air-cooled. Originally designed to be water-cooled, named Aquarius, ECL macrocell array CPU, VAXBI, October 1989[2])
    • VAX 9000 Model 110
    • VAX 9000 Model 210
    • VAX 9000 Model 310
    • VAX 9000 Model 4x0 (x = number of processors, 1–4)

[edit] A transitional VAX

  • MicroVAX/VAXstation I (Seahorse, October 1984)

[edit] VLSI VAXen

  • MicroVAX series (some models also sold as VAXservers)
    • MicroVAX II (Mayflower, May 1985)
    • MicroVAX III (BA23- or BA123-enclosure MicroVAX upgraded with KA650 CVAX CPU)
    • MicroVAX III+ (BA23- or BA123-enclosure MicroVAX upgraded with KA655 CPU)
    • VAX 4 (BA23- or BA123-enclosure MicroVAX upgraded with KA660 CPU)
    • MicroVAX 2000 (TeamMate, desktop form factor, February 1987)
    • MicroVAX 3100 series (desktop form-factor, 1987 onwards)
      • MicroVAX 3100 Model 10 (TeamMate II, KA41-A CVAX processor)
      • MicroVAX 3100 Model 10e (TeamMate II, KA41-D CVAX+ processor)
      • MicroVAX 3100 Model 20 (Model 10 in larger enclosure)
      • MicroVAX 3100 Model 20e (Model 20 in larger enclosure)
      • MicroVAX 3100 Model 30 (Waverley/S, KA45 SOC CPU)
      • MicroVAX 3100 Model 40 (Model 30 in larger enclosure)
      • MicroVAX 3100 Model 80 (Waverley/M, KA47 Mariah CPU)
      • MicroVAX 3100 Model 85 (Waverley/M+, KA55 NVAX CPU)
      • MicroVAX 3100 Model 88 (Waverley/M+, KA58 NVAX CPU)
      • MicroVAX 3100 Model 90 (Cheetah, KA50 NVAX CPU)
      • MicroVAX 3100 Model 95 (Cheetah+, KA51 NVAX CPU)
      • MicroVAX 3100 Model 96 (Cheetah++, KA56 NVAX CPU)
      • MicroVAX 3100 Model 98 (Cheetah++, KA59 NVAX CPU)
    • MicroVAX 3300/3400 (Mayfair, used KA640 CPU card)
    • MicroVAX 3500/3600 (Mayfair-II, used KA650 CPU card, September 1987)
    • MicroVAX 3800/3900 (Mayfair-III, used KA655 CPU card)
  • VAXstation series
    • VAXstation II (MicroVAX II workstation configuration)
    • VAXstation II/GPX (Caylith, hardware-enhanced, high-performance color graphics, December 1985)
    • VAXstation 2000 (VAXstar MicroVAX 2000 workstation configuration)
    • VAXstation 3100 series
      • VAXstation 3100 Model 30 (PVAX, KA42-A CVAX CPU)
      • VAXstation 3100 Model 38 (PVAX rev#7, KA42-B CVAX CPU)
      • VAXstation 3100 Model 40 (Model 30 in larger enclosure)
      • VAXstation 3100 Model 48 (Model 38 in larger enclosure)
      • VAXstation 3100 Model 76 (RigelMAX, KA43-A Rigel CPU)
      • VT1300 (X terminal; essentially a diskless VAXstation 3100 Model 30)
    • VAXstation 3200/3500 (Mayfair/GPX, KA650 CVAX CPU)
    • VAXstation 3520/3540 (Firefox, two or four KA60 CVAX processors)
    • VAXstation 4000 (TURBOchannel bus)
      • VAXstation 4000/VLC aka Model 30 (PVAX2/VLC, KA48 SOC ("System On Chip") CPU, slim pizza box, accepting standard 72pin parity SIMM modules)
      • VAXstation 4000 Model 60 (PMariah, KA46 Mariah CPU)
      • VAXstation 4000 Model 90 (Cougar, KA49-A NVAX CPU)
      • VAXstation 4000 Model 90A (Cougar+, KA49-A NVAX CPU)
      • VAXstation 4000 Model 96 (Cougar++, KA49-C NVAX CPU)
    • VAXstation 8000 (Lynx, very rare high-end 3D workstation based on VAX 8200)
  • VAX 4000 series (MicroVAX name dropped):
    • VAX 4000 Model 50 (VAXbrick, KA600 NVAX processor, CPU upgrade for MicroVAX 3x00 or VAX 4000-200)
    • VAX 4000 Model 100/100A (Cheetah-Q, KA52 NVAX processor)
    • VAX 4000 Model 105A (Cheetah-Q+, faster KA53 NVAX processor)
    • VAX 4000 Model 106A/108 (Cheetah-Q++, faster KA54/KA57 NVAX processor)
    • VAX 4000 Model 200 (Spitfire, KA660 SOC processor)
    • VAX 4000 Model 300 (Pele, KA670 Rigel 1.5 μm CMOS processor chipset[3], mid-1989)
    • VAX 4000 Model 400 (Omega, KA675 NVAX processor)
    • VAX 4000 Model 500/500A (Omega/N, KA680/KA681 NVAX processor)
    • VAX 4000 Model 505A/600/600A (Omega/N+, KA690/KA691 NVAX processor)
    • VAX 4000 Model 700A (Legacy, KA692 NVAX processor)
    • VAX 4000 Model 705A (Legacy+, KA694 NVAX processor)
  • VAX 8200 and VAX 8300 (Single- and dual-processor Scorpio, VAXBI backplane, January 1986)
  • VAX 8250 and VAX 8350 (Faster Scorpios)
  • VAX 6000 series (x = number of processors, max 6 for 600 series):
    • VAX 6000 Model 2x0 aka VAX 62x0 series (Calypso, (used CVAX chipset, April 1988)
    • VAX 6000 Model 3x0 aka VAX 63x0 series (Hyperion, CVAX+ 1.5 μm CMOS processor chipset, January 1989)
    • VAX 6000 Model 4x0 aka VAX 64x0 series (Calypso/XRP, Rigel 1.5 μm CMOS chipset, mid-1989)
    • VAX 6000 Model 5x0 aka VAX 65x0 series (Calypso/XMP, Mariah 1.0 μm CMOS chipset, October 1990)
    • VAX 6000 Model 6x0 aka VAX 66x0 series (Neptune, NVAX 0.75 μm CMOS chipset, November 1991)
    • VAX 6333 (prepackaged cluster of VAX 6000 Model 300 series)
  • VAX 7000 series:
    • VAX 7000 Model 6x0 (Laser/Neon, Up to six NVAX+ processors, field-upgradable to Alpha AXP 64-bit processor(s) (ie. DEC 7000 AXP configuration), July 1992)
    • VAX 7000 Model 7x0 (Laser/Krypton, NVAX5 processors(s))
    • VAX 7000 Model 8x0 (Laser/Krypton+, faster NVAX5 processor(s))
  • VAX 10000 Model 6x0 (Blazer, similar to VAX 7000 Model 6x0)
  • VAXft fault-tolerant series:
    • VAXft 3000 Model 310 (Cirrus, CVAX+ CPUs, two-processor, lock-stepped fault tolerant system, February 1990)
    • VAXft Model 110 (slower, lower cost Cirrus)
    • VAXft Model 410/610/612 (Cirrus II, SOC CPUs)
    • VAXft Model 810 (Jetstream, NVAX+ CPUs)
  • VAX XXXX    (BVAX, High-end VAX; Never shipped)
This list is incomplete; you can help by expanding it.

[edit] References

  1. ^ VAX timeline, Hewlett Packard website
  2. ^ DIGITAL Computing Timeline
  3. ^ Trailing edge, The Computer History Simulation Project

[edit] External links

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