The rise and fall of plug-compatible mainframes

The rise and fall of plug-compatible mainframes spanned more than 20 years. RCA, whose 1964 Spectra 70 system was compatible with the IBM System/360, chose another path altogether, so Amdahl in 1970 became the first true PCM manufacturer. Other companies notably Fujitsu and Hitachi-soon followed, seeking to compete with IBM in the mainframe arena. This article traces the history of PCMs, which includes an intriguing incident of industrial espionage.