Editing VMEbus (section)

== 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.<ref>{{cite book|last=Black|first=John Arthur|title=The System engineer's handbook: a guide to building VMEbus and VXIbus systems|year=1992|publisher=[[Morgan Kaufmann Publishers|Morgan Kaufmann]]|isbn=978-0-12-102820-6|page=563|quote=A team of engineers at Motorola Microsystems led by Jack Kister, designed a 68000 development system called the EXORmacs. The backplane of the EXORmacs was called VERSAbus. While coordinating the efforts of his team, Jack wrote a 41-page bus description of VERSAbus which was published in November of 1979. The first EXORmacs was shipped in January 1980.}}</ref> The Motorola team brainstormed for days to select the name VERSAbus. VERSAbus cards were large, {{convert|14+1/2|by|9+1/4|in|mm|order=flip|abbr=on}}, and used [[edge connector]]s.<ref name="vitavme">{{cite web |date=3 January 1999 |title=VME Technology FAQ |url=http://www.vita.com/page-1855175 |access-date=1 August 2013 |publisher=Vita.com}}</ref> Only a few products adopted it, including the [[IBM System 9000]] instrument controller and the [[Automatix]] robot and machine vision systems.

[[File:VERSAbus memory card.agr.jpg|thumb|left|VERSAbus memory card]]
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 (printed circuit board)|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 Europa'').<ref name="vitavme" />

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 [[International Electrotechnical Commission|IEC]] as the IEC 821 VMEbus and by ANSI and IEEE as ANSI/IEEE 1014-1987.

The original standard was a [[16-bit]] bus, designed to fit within the existing Eurocard [[DIN]] connectors. However, there have been several updates to the system to allow wider bus widths. The current ''VME64'' includes a full [[64-bit]] bus in 6U-sized cards and [[32-bit]] in 3U cards. The VME64 protocol has a typical performance of 40 [[megabyte|MB]]/s.<ref name="vitavme" /> Other associated standards have added hot-swapping ([[plug-and-play]]) 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.<ref name="vitavme" /> 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,<ref name="vitavme" /> developed in the late 1970s by Motorola. This was later renamed "VME", short for Versa Module European, by Lyman (Lym) Hevle, then a VP with the Motorola Microsystems Operation. (He was later the founder of the VME Marketing Group, itself subsequently renamed to VME International Trade Association, or VITA). 

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{{nbsp}}× 160{{nbsp}}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 bus|serial]] and [[parallel bus|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.

{| class="wikitable"
|+ Evolution of VME
|-
! Topology
! Year
! Bus cycle
! Maximum speed (MB/s)
|-
| VMEbus32 Parallel Bus Rev. A
| 1981
| {{abbr|2=BLock Transfer|BLT}}
| 40
|-
| VMEbus IEEE-1014
| 1987
| {{abbr|2=BLock Transfer|BLT}}
| 40
|-
| [[VME64]]
| 1994
| {{abbr|2=Multiplexed BLock Transfer (data over address lines, too)|MBLT}}
| 80
|-
| [[VME64x]]
| 1997 
| [[2eVME]]
| 160
|-
| [[VME320]]
| 1997 
| [[2eSST]]
| 320
|}