The IBM 7080 was a variable word length BCD transistor computer

Transistor computer

A transistor 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, were bulky, and were unreliable. A "second generation" of computers, through the late 1950s and...

 in the IBM 700/7000 series

IBM 700/7000 series

The IBM 700/7000 series was a series of large-scale computer systems made by IBM through the 1950s and early 1960s. The series included several different, incompatible processor architectures. The 700s used vacuum tube logic and were made obsolete by the introduction of the transistorized 7000s...

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

Vacuum tube

In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

 IBM 705 computer.

After the introduction of the IBM 7070

IBM 7070

IBM 7070 was a decimal architecture intermediate data processing system that was introduced by IBM in June 1960. 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...

, in June 1960, as an upgrade path for both the IBM 650

IBM 650

The IBM 650 was one of IBM’s early computers, and the world’s first mass-produced computer. It was announced in 1953, and over 2000 systems were produced between the first shipment in 1954 and its final manufacture in 1962...

 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 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

Punched card input/output

A punched card reader or just card reader is a computer input device used to read data from punched cards. A card punch is a output device that punches holes in cards under computer control...

, line printers and the IBM 727

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 computers used the IBM 729-series tape drive...

 magnetic tape drives, to be used on the 7080. Second generation IBM 729

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...

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