ES EVM

The ES EVM (Russian: Единая система электронных вычислительных машин (ЕС ЭВМ), romanized: Yedinaya sistema electronnykh vytchislitel'nykh mashin (ES EVM), "Unified System of Electronic Computing Machines"), or YeS EVM, also known in English literature as the Unified System or Ryad (Russian: Ряд, "Series"), is a series of mainframe computers generally compatible with IBM's System/360 and System/370 mainframes, built in the Comecon countries under the initiative of the Soviet Union between 1968 and 1998.

With the exception of only a few hardware pieces, the ES EVM machines were recognized in the Western countries as independently designed, based on legitimate Soviet patents.

[1] 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.

The former German chancellor Angela Merkel, used one of East Germany's ES EVM computers in 1986 for her PhD dissertation.