VMEbus (VERSAmodule Eurocard bus bus) is a computer bus standard physically based on Eurocard sizes.
History In 1979, during development of the Motorola 68000 CPU, one of their engineers, Jack Kister, decided to set about creating a standardized bus system for 68000-based systems. The Motorola team brainstormed for days to select the name VERSAbus. VERSAbus cards were large, 370 by 230 mm (14+1⁄2 by 9+1⁄4 in), and used edge connectors. Only a few products adopted it, including the IBM System 9000 instrument controller and the Automatix robot and machine vision systems.
Kister was later joined by John Black, who refined the specifications and created the VERSAmodule product concept. A young engineer working for Black, Julie Keahey designed the first VERSAmodule card, the VERSAbus Adaptor Module, used to run existing cards on the new VERSAbus. Sven Rau and Max Loesel of Motorola-Europe added a mechanical specification to the system, basing it on the Eurocard standard that was then late in the standardization process. The result was first known as VERSAbus-E but was later renamed to VMEbus, for VERSAmodule Eurocard bus (although some refer to it as Versa Module Europe or Versa Module European). At this point, a number of other companies involved in the 68000's ecosystem agreed to use the standard, including Signetics, Philips, Thomson, and Mostek. Soon it was officially standardized by the IEC as the IEC 821 VMEbus and by ANSI and IEEE as ANSI/IEEE 1014-1987. The original standard described a bus with up to 16-bit width, designed to fit within the existing Eurocard DIN connectors and which has a maximum transfer bandwidth of 40 MB/s. However, there have been several updates to the system to allow wider bus widths. The current VME64 supports up to 64-bit bus width in 6U-sized cards and 32-bit in 3U cards. Doubling the bus width also doubles the maximum transfer bandwidth of VME64 to 80 MB/s. Other associated standards have added hot-swapping (plug-and-play) and doubling bandwidth in VME64x, smaller 'IP' cards that plug into a single VMEbus card, and various interconnect standards for linking VME systems together. In the late 1990s, synchronous protocols proved to be favourable. The research project was called VME320. The VITA Standards Organization called for a new standard for unmodified VME32/64 backplanes. The new 2eSST protocol was approved in ANSI/VITA 1.5 in 1999. Over the years, many extensions have been added to the VME interface, providing 'sideband' channels of communication in parallel to VME itself. Some examples are IP Module, RACEway Interlink, SCSA, Gigabit Ethernet on VME64x Backplanes, PCI Express, RapidIO, StarFabric and InfiniBand. VMEbus was also used to develop closely related standards, VXIbus and VPX. The VMEbus had a strong influence on many later computer buses such as STEbus.
VME early years The architectural concepts of the VMEbus are based on VERSAbus, developed in the late 1970s by Motorola. This was later renamed "VME", short for VERSAmodule Eurocard, by Lyman (Lym) Hevle, then a VP with the Motorola Microsystems Operation. Lyman was later in 1982 the founder of the VMEbus Marketing Group, itself subsequently renamed to VMEbus International Trade Association in 1984/1985, since shortened to VITA in 2005. John Black of Motorola, Craig MacKenna of Mostek and Cecil Kaplinsky of Signetics developed the first draft of the VMEbus specification. In October 1981, at the System '81 trade show in Munich, West Germany, Motorola, Mostek, Signetics/Philips, and Thomson CSF announced their joint support of the VMEbus. They also placed Revision A of the specification in the public domain. In 1985, Aitech developed, under contract for US Army TACOM, the first conduction-cooled 6U VMEbus board. Although electrically providing a compliant VMEbus protocol interface, mechanically, this board was not interchangeable for use in air-cooled lab VMEbus development chassis. In late 1987, a technical committee was formed under VITA under the direction of IEEE to create the first military, conduction-cooled 6U × 160 mm, fully electrically and mechanically compatible, VMEbus board co-chaired by Dale Young (DY4 Systems) and Doug Patterson (Plessey Microsystems, then Radstone Technology). ANSI/IEEE-1101.2-1992 was later ratified and released in 1992 and remains in place as the conduction-cooled, international standard for all 6U VMEbus products. In 1989, John Peters of Performance Technologies Inc. developed the initial concept of VME64: multiplexing address and data lines (A64/D64) on the VMEbus. The concept was demonstrated the same year and placed in the VITA Technical Committee in 1990 as a performance enhancement to the VMEbus specification. In 1993, new activities began on the base-VME architecture, involving the implementation of high-speed serial and parallel sub-buses for use as I/O interconnections and data mover subsystems. These architectures can be used as message switches, routers and small multiprocessor parallel architectures. VITA's application for recognition as an accredited standards developer organization of ANSI was granted in June 1993. Numerous other documents ( including mezzanine, P2 and serial bus standards) have been placed with VITA as the Public Domain Administrator of these technologies.
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