The VAX-11 is a discontinued family of

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...

superminicomputers, running the Virtual Address eXtension (VAX)

instruction set architecture In computer science, an instruction set architecture (ISA), also called computer architecture, is an abstract model of a computer. A device that executes instructions described by that ISA, such as a central processing unit (CPU), is called an ' ...

(ISA), developed and manufactured by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

(DEC). Development began in 1976. In addition to being powerful machines in their own right, they also offer the additional ability to run user mode

PDP-11 The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold, ...

code (thus the -11 in VAX-11), offering an upward compatible path for existing customers. The first machine in the series, the VAX-11/780, was announced in October 1977. Its former competitors in the minicomputer space, like Data General and

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

, were unable to successfully respond to the introduction and rapid update of the VAX design. DEC followed the VAX-11/780 with the lower-cost 11/750, and the even lower cost 11/730 and 11/725 models in 1982. More powerful models, initially known as the VAX-11/790 and VAX-11/795, were instead rebranded as the VAX 8600 series. The VAX-11 line was discontinued in 1988, having been supplanted by the MicroVAX family on the low end, and the

VAX 8000 The VAX 8000 is a discontinued family of superminicomputers developed and manufactured by Digital Equipment Corporation (DEC) using processors implementing the VAX instruction set architecture (ISA). The 8000 series was introduced in October 1984 ...

family on the high end. The VAX-11/780 is historically one of the most successful and studied computers in history.

VAX-11/780

The VAX-11/780, code-named "Star", was introduced on 25 October 1977 at DEC's Annual Meeting of Shareholders. It is the first computer to implement the VAX architecture. The KA780

central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

(CPU) is built from Schottky transistor-transistor logic (TTL) devices and has a 200 ns cycle time (5 MHz) and a 2 KB cache. Memory and I/O are accessed via the

Synchronous Backplane Interconnect The Synchronous Backplane Interconnect (SBI) was the internal processor-memory bus used by early VAX computers manufactured by the Digital Equipment Corporation of Maynard, Massachusetts. The bus was implemented using Schottky TTL logic levels a ...

(SBI). The VAX-11/780 originally supported up to 8MB of memory through one or two MS780-C memory controllers, with each controller supporting between 128KB-4MB of memory. The later MS780-E memory controller supports 4MB-64MB of memory, allowing the VAX-11/780 to support up to a total of 128MB of memory. The KA780 has a 29-bit physical address space, allowing it to address a theoretical maximum of 512MB of memory. The memory is constructed from 4 or 16 kbit

metal oxide semiconductor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

(MOS) RAM chips mounted on memory array cards. Each memory controller controls up to 16 array cards. The memory is protected by error correcting code (ECC). The VAX-11/780 uses the Unibus and Massbus for I/O. Unibus is used for attaching lower-speed peripherals such as terminals and printers and Massbus for higher-speed disk and tape drives. Both buses are provided by adapters that interface the bus to the SBI. All systems come with one Unibus as standard, with up to four supported. Massbus is optional, with up to four supported. The VAX-11/780 also supports Computer Interconnect (CI), a proprietary network to attach disk drives and potentially share them with other VAX computers. This feature can connect VAX computers in a

VMScluster A VMScluster, originally known as a VAXcluster, is a computer cluster involving a group of computers running the OpenVMS operating system. Whereas tightly coupled multiprocessor systems run a single copy of the operating system, a VMScluster is l ...

. Digital used the performance of the VAX-11/780 as a reference point for describing the performance of subsequent VAX models. The performance of the VAX-11/780 became known as 1

VAX Unit of Performance The VAX Unit of Performance, or VUP for short, is an obsolete measurement of computer performance used by Digital Equipment Corporation (DEC). 1 VUP was equivalent to the performance of a VAX 11/780 completing a given task. Other VAX machines an ...

(or 1.0 VUPs). Other VAX models are rated as a multiple of the VAX-11/780's performance, for example, a 2.0 VUPs VAX is twice as fast as the VAX-11/780.

VAX-11/782

The VAX-11/782, code-named "Atlas", is a dual-processor VAX-11/780 introduced in 1982. Both processors share the same MA780 multiport memory bus and the system operates asymmetrically, with the primary CPU performing all I/O operations and process scheduling with the second, attached processor only used for additional computationally-intensive work. For multistream computation-intensive tasks the system delivers up to 1.8 times the performance of a VAX 11/780.

VAX-11/784

The VAX-11/784, code-named "VAXimus", is a rare quad-processor variant of the VAX-11/780. Similar to the VAX-11/782, it is an asymmetric multiprocessing system, with all four KA780 processors sharing the same MA780 multiport memory bus. Its performance is rated as 3.5 VUPs.

VAX-11/785

The VAX-11/785, code-named "Superstar", was introduced in April 1984. Its KA785 CPU is essentially a faster KA780, with a CPU cycle time of 133 ns (7.52 MHz) versus the 200 ns (5 MHz) CPU cycle time of the KA780, giving a performance of 1.5 VUPs. The decrease in CPU cycle time is accomplished through use of Fairchild Advanced Schottky TTL (FAST) logic.

VAX-11/787

The VAX-11/787 is a possible dual-processor variant of the VAX-11/785. It is unclear whether any were produced.

VAX-11/750

The VAX-11/750, code-named "Comet", is a more compact, lower-performance

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gate array–based implementation of the VAX architecture introduced in October 1980. The use of gate arrays decreases power consumption, and increases reliability compared with the VAX-11/780. The KA750 CPU has a 320 ns cycle time (3.125 MHz), and a VUPs rating of 0.6. The system can support up to 2MB with an L0011 memory controller, up to 8MB with an L0016 memory controller, or up to 14MB with an L0022 memory controller.

VAX-11/751

A ruggedized rack-mount VAX-11/750.

VAX-11/730

Introduced in April 1982, the VAX-11/730, code-named "Nebula", is a still-more-compact, still-lower-performance

bit slice Bit slicing is a technique for constructing a Processor (computing), processor from modules of processors of smaller bit width, for the purpose of increasing the word length; in theory to make an arbitrary ''n''-bit central processing unit ( ...

implementation of the VAX architecture using AMD Am2900 chips for the CPU. The KA730 CPU has a 270 ns cycle time (3.70 MHz), and a VUPs rating of 0.3. It supports up to 5MB of memory.

VAX-11/725

Code-named "LCN" ("Low-Cost Nebula"), it is a cost-reduced model of the VAX-11/730. It uses the same KA730 CPU as the VAX-11/730, but is housed in a more compact enclosure designed to reduce noise and heat ("55 dB" and "575 W (max.)"), making it more suitable for use in an office environment. It supports up to 3MB of memory.

VAX-11/790 and VAX-11/795

The VAX-11/790 and VAX-11/795 are the original names for the VAX 8600 and VAX 8650 respectively.

Remaining machines

* The Living Computer Museum of Seattle, Washington maintains a VAX-11/780-5 (field-upgraded VAX-11/780) running

OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...

7.3. * The

Computer History Museum The Computer History Museum (CHM) is a museum of computer history, located in Mountain View, California. The museum presents stories and artifacts of Silicon Valley and the information age, and explores the computing revolution and its impact on ...

of Mountain View, California has three VAX-11/780 systems, one VAX-11/725, one VAX-11/730, and one VAX-11/750 within its permanent collection. * The RECHENWERK Computer & Technikmuseum Halle in Halle, Germany holds a VAX-11/730 and a very rare East German clone of a VAX-11/780 named Robotron K 1840 in its permanent exhibition. * Th
Verde Binario
retrocomputing association has a VAX-11/780 to which they dedicated a calendar. * Th
Large Scale Systems Museum
in New Kensington, PA has a VAX-11/780. * The Luddy School of Informatics, Computing, and Engineering at IU Bloomington in Indiana has on display a VAX-11/780, as well as various other computers from the time.

References

{{Authority control DEC minicomputers Computer-related introductions in 1977 Computers using bit-slice designs