IBM 7074

IBM 7070 was a decimal architecture intermediate data processing system that was introduced by IBM in 1958. It was part of the IBM 700/7000 series, and was based on discrete transistors rather than the vacuum tubes of the 1950s. It was the company's first transistorized stored-program computer.

The 7070 was expected to be a "common successor to at least the 650 and the 705". The 7070 was not designed to be instruction set compatible with the 650, as the latter had a second, jump address in every instruction to allow optimal use of the drum, something unnecessary and wasteful in a computer with random access core memory. As a result, a simulator was needed to run old programs. The 7070 was also marketed as an IBM 705 upgrade, but failed miserably due to its incompatibilities, including an inability to fully represent the 705 character set; forcing IBM to quickly introduce the IBM 7080 as a "transistorized IBM 705" that was fully compatible.

The 7070 series stored data in a 10 decimal digit plus sign word. Digits were encoded using a two-out-of-five code. Characters were represented by a two-digit code. The machine shipped with 5,000 to 9,990 words of core and the CPU speed was about 27KIPS. A typical system was leased for $17,400 per month or could be purchased for $813,000.

Later systems in this series were the faster IBM 7074 introduced in July 1960 and the IBM 7072 (1961). They were eventually replaced by the System/360, announced in 1964.

The 7070 was implemented using both CTDL (in the logic and control sections) and current mode logic (in the timing storage and core storage sections) on Standard Modular System (SMS) cards. A total of about 30,000 alloy-junction germanium transistors and 22,000 germanium diodes are used, on approx 14,000 SMS cards.

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