VAX
History
The first VAX with the type designation 11/780 came in October 1977 on the market. In February 1978, a special operating system for the VAX called VMS (Virtual Memory System) was completed, its development was started at the same time. VAX computers were sold until 2000. Today, the computer architecture is still in the military area in front, for example, in the fighter aircraft F -15 and F/A-18 manufacturer McDonnell Douglas (now Boeing ) or in the Minuteman intercontinental ballistic missile system.
Main architect was William D. Strecker, a former graduate student of Gordon Bell.
Features
One of the main goals in the specification of the VAX architecture was to expand the 16- bit address space of its predecessor, the PDP -11 to 32 bits, so an extension of directly addressable from 64 kB to - future proof for that time - 4 GB. Originally, the VAX architecture should only be a modified PDP -11 architecture with hardware to support virtual memory management, hence the name VAX (extension to virtual addresses). During the initial development was, however, decided to create a new architecture that provides incompatible, but also additional instructions, data types and addressing modes compared to other PDP -11.
In the design of VMS was taken on source code compatibility with older operating systems in order to implement existing programs and data with little effort on the new system. Optional possessed some VAX a binary compatibility mode, could be carried out directly in the PDP -11 programs. Because VMS is a particularly stable and mature operating system, it has been found mainly in the financial sector and in the air traffic control ( civil and military) a very wide spread and is still further developed as OpenVMS (also for other hardware platforms). The current license holder HP told on June 10, 2013, that he will support OpenVMS until the end of 2020. The future is uncertain after that.
19 "cabinets with VAX11/751 and Megatek graphic (left), tape and disk drives ( right), before Konsoldrucker (University of Kassel)
Processor
The 32 -bit VAX CPUs were based on a CISC instruction set of the instruction set of the m68k processors from Motorola is similar due to the common PDP-11 prototype, but additional commands to the operating system support, such as queue management, bot. The processor family has been replaced by the also developed by DEC Alpha processor, a 64 -bit RISC processor.
VAX computers were on the PDP computers the first computer on the Unix operating system was ported. Digital Equipment offered its own UNIX derivative called ULTRIX next to the proprietary VMS operating system. Meanwhile, the open- source operating systems NetBSD, OpenBSD and Linux have been ported to the VAX computer.
Originally the computer from standard components, such as bit-slices and TTL logic circuits were built. Later developed their own digital VAX microprocessors, called MicroVAX processors such as the MicroVAX 78032 or CVAX that were not sold on the open market. They were available only with computers of the MicroVAX family.
The software SIMH can emulate a complete MicroVAX 3900 system.