The IBM 7080 was a variable word length BCD

transistor computer A transistor computer, now often called a second-generation computer, is a computer which uses discrete transistors instead of vacuum tubes. The first generation of electronic computers used vacuum tubes, which generated large amounts of heat, ...

in the

IBM 700/7000 series The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube lo ...

commercial architecture line, introduced in August 1961, that provided an upgrade path from the

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

IBM 705 The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube lo ...

computer. The 7080 weighed about . After the introduction of the

IBM 7070 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 compa ...

, in June 1960, as an upgrade path for both the IBM 650 and IBM 705 computers, IBM realized that it was so incompatible with the 705 that few users of that system wanted to upgrade to the 7070. That prompted the development of the 7080, which was fully compatible with all models of the 705 and added many improvements.

IBM 705 compatibility modes

For

backward compatibility Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especiall ...

with the IBM 705 the machine had two switches on the operator's control panel, ''705 I-II'' and ''40K memory'', that selected the mode the machine started in. *705 I mode — 20,000 characters (''705 I-II'' On, ''40K memory'' Off) **Indirect addressing is disabled **Communication channels are disabled *705 II mode — 40,000 characters (''705 I-II'' On, ''40K memory'' On) **Indirect addressing is disabled **Communication channels are disabled *705 III mode — 40,000 characters (''705 I-II'' Off, ''40K memory'' On) **Indirect addressing is enabled **Communication channels are enabled *705 III mode — 80,000 characters (''705 I-II'' Off, ''40K memory'' Off) **Indirect addressing is enabled **Communication channels are enabled Software can then command the 7080 to enter full 7080 mode from any 705 startup mode. *7080 mode — 160,000 characters **Indirect addressing is disabled **Communication channels are enabled Regardless of mode, the 7080 operates at full 7080 speed. The 7080 system included the IBM 7622 Signal Control, which converted transistor signal levels to levels usable with first generation equipment, allowing all 705 peripherals, including

punched card input/output A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards. A computer card punch is a computer output device that punches ...

, line printers and the

IBM 727 The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum-tube era computer systems. Later vacuum-tube machines and first-generation transistor c ...

magnetic tape drives, to be used on the 7080. Second generation

IBM 729 The IBM 729 Magnetic Tape Unit was IBM's iconic tape mass storage system from the late 1950s through the mid-1960s. Part of the IBM 7 track family of tape units, it was used on late 700, most 7000 and many 1400 series computers. Like its prede ...

tape drives connected to the CPU via the IBM 7621 Tape Control.

References

External links

IBM 7080 documents on Bitsavers.org
– Includes a cross assembler for the IBM 705/7080
BIRTH OF AN UNWANTED IBM COMPUTER Computer History Vignettes By Bob Bemer
IBM 7070 connection to IBM 7080 7080 7 7080 Variable word length computers Computer-related introductions in 1961 {{mainframe-compu-stub