ES EVM

ES EVM (ЕС ЭВМ, Единая система электронных вычислительных машин, Edinaya Sistema Electronnykh Vytchislitel'nykh Mashin, meaning "Unified System of Electronic Computers") was a series of clones of IBM's System/360 and System/370 mainframes, released in the Comecon countries under the initiative of the Soviet Union since the 1960s. Production continued until 1998. The total number of ES EVM mainframes produced was more than 15,000.

In the period from 1986 to 1997, there were also produced a series of PC-compatible desktop computers, called ЕС ПЭВМ (Unified System of Personal Computers); the newer versions of these computers are still produced under a different name on a very limited scale in Minsk.

In 1966, the Soviet economists suggested creating a unified series of mutually compatible computers. Due to the success of the IBM System/360 in the USA, the economic planners decided to use the IBM design, although some prominent Soviet computer scientists had criticized the idea and suggested instead choosing one of the Soviet indigenous designs, such as БЭСМ or Minsk. The first works on the cloning began in 1968; production started in 1972. In addition, after 1968, other Comecon countries joined the project.

During the 1960s–1970s, several other companies, such as Amdahl, Siemens and Hitachi, had also cloned the IBM architecture without IBM's approval. With the exception of only a few hardware pieces, the ES machines were recognized in the Western countries as independently designed, based on legitimate Soviet patents. Unlike the hardware, which was quite original, mostly created by reverse-engineering, much of the software was based on slightly modified and localized IBM code. In 1974–1976, IBM had contacted the Soviet authorities and expressed interest in ES EVM development; however, after the Soviet Army entered Afghanistan, in 1979, all contacts between IBM and ES developers were interrupted, due to the U.S. embargo on technological cooperation with the USSR.

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