|
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.
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. 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. 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*. 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*. By 2005 all manufacturing of VAX computers had ceased, but old systems remained in widespread use. Trivia The phrase, "CVAX — when you care enough to steal the very best" ("", a play on the well-known Hallmark Cards slogan*) was written in poor Russian on the Digital CVAX microprocessor used in the MicroVAX 3000 and 6200 *. It was intended to send a special message to Soviet engineers attempting to reverse engineer DEC's chip design. 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: Non-VLSI VAXen A transitional VAX VLSI VAXen | ||||||||
|
| |||||||||
 |
|
| |