The IBM 7090 was a second-generation transistorized version of the earlier IBM 709 vacuum tube mainframe computers and was designed for "large-scale scientific and technological applications", was the third member of the IBM 700/7000 series scientific computers. The first 7090 installation was in November 1959.
The 7090 used a 36-bit word length, with an address-space of 32K (32,768) words. It operated with a basic memory cycle of 2.18 μs, using core memory technology from the IBM 7030 (Stretch) project.
IBM 7094
An upgraded version, the IBM 7094. was first installed in September 1962. In April 1964, the first 7094 II was installed, which had almost twice as much general speed as the 7090 due to a faster clock cycle and introduction of overlapped instruction execution. The 7094 had additional instructions, but was largely backward compatible with the 7090, though minor changes in instruction formats, particularly the additional index registers, sometimes caused problems.
Instruction Format
The basic instruction format was a 3-bit prefix, 15-bit decrement, 3-bit tag, and 15-bit address. The prefix field specified the class of instruction. The decrement field often contained an immediate operand to modify the results of the operation, or was used to further define the instruction type. The three bits of the tag specified three index registers (seven in the 7094), the contents of which were subtracted from the address to produce an effective address. The address field either contained an address or an immediate operand.
Notable applications
- The Compatible Time-Sharing System (CTSS), one of the first time-sharing operating systems, was developed at MIT's Project MAC using a modified 7094 with an extra bank of memory.
- NASA used 7090s, and, later, 7094s to control the Mercury and Gemini space flights. During the early Apollo Program, a 7094 was kept operational to run flight planning software that had not yet been ported to mission control's newer System/360 computers.
- The US Air Force retired its last 7094s in service from the Ballistic Missile Early Warning System ("BMEWS") in the 1980s after almost 30 years of use.
- The US Navy continued to use a 7094 at Pacific Missile Test Center, Point Mugu, California through much of the 1980s, although a "retirement" ceremony was held in July 1982. Not all of the applications had been ported to its successor, a dual-processor CDC Cyber 175.