The IBM System/360 Model 91 was announced in 1964 as a competitor to the

CDC 6600 The CDC 6600 was the flagship of the 6000 series of mainframe computer systems manufactured by Control Data Corporation. Generally considered to be the first successful supercomputer, it outperformed the industry's prior recordholder, the IBM ...

. Functionally, the Model 91 ran like any other large-scale

System/360 The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...

, but the internal organization was the most advanced of the System/360 line, and it was the first IBM computer to support out-of-order instruction execution. It ran OS/360 as its operating system. It was designed to handle high-speed data processing for scientific applications. This included

space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by uncrewed robo ...

, theoretical astronomy, sub-atomic physics and global weather forecasting. The first Model 91 was used at the

NASA Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

in 1968 and at the time was the most powerful computer in user operation. It was capable of executing up to 16.6 million instructions per second, making it roughly equivalent to an intel 80486SX-20 MHz CPU or AMD 80386DX-40 MHz CPU in MIPS performance. The CPU consisted of five autonomous units: instruction, floating-point, fixed-point, and two storage controllers for the overlapping memory units and the I/O data channels. The

floating-point unit In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

made heavy use of instruction pipelining and was the first implementation of Tomasulo's algorithm. It was also one of the first computers to utilize multi-channel memory architecture.

Models

There were four models of the IBM System/360 Model 91. They differed by their main memory configuration, all using IBM's 2395 Processor Storage. The 91K had 2 MB, using one 2395 Model 1. Both the 91KK and the 91L came with 4 MB of main memory: the former used a pair of 2395 Model 1s, the latter a single 2395 Model 2. The 6 MB KL was equipped with one Model 1 and one Model 2 IBM 2395s.

Models built

There were only 15 Model 91s ever produced, four of which were for IBM's internal use. After quoting from Pugh et al, William H. Blair says "Many disagree on the number of 360/91s that IBM built or sold. I have read and heard it authoritatively stated that the number was 10, 11, 12, 14, 15, or 20." As for those delivered to customers, "a 360/85 was delivered from when a 91 was ordered until it was ready."

IBM and NASA

IBM had a long history with

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

including the use of IBM components on manned space flights such as the IBM ASC-15 on

Saturn 1 The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to low Earth orbit payloads.Terminology has changed since the 1960s; back then, 20,000 pounds was considered "heavy lift". The rocket's first sta ...

, the IBM ASC-15B on the Titan Family, IBM GDC on Gemini, IBM LVDC on Saturn 1B/5,

IBM System/4 Pi The IBM System/4 Pi is a family of avionics computers used, in various versions, on the F-15 Eagle fighter, E-3 Sentry AWACS, Harpoon Missile, NASA's Skylab, MOL, and the Space Shuttle, as well as other aircraft. Development began in 1965, del ...

-EP on the MOL, and the IBM System/4 Pi-TC 1 on the

Apollo Telescope Mount The Apollo Telescope Mount, or ATM, was a crewed solar observatory that was a part of Skylab, the first American space station. It could observe the Sun in wavelengths ranging from soft X-rays, ultra-violet, and visible light. The ATM was man ...

and

Skylab Skylab was the first United States space station, launched by NASA, occupied for about 24 weeks between May 1973 and February 1974. It was operated by three separate three-astronaut crews: Skylab 2, Skylab 3, and Skylab 4. Major operations ...

. The Model 91 was shipped 9 months late to the

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

in October 1967 and did not begin regular operations until January 1968 after it passed the federal government operations testing.

IBM System/360 Model 95

The Model 95 was a variant of the Model 91 with 1 megabyte of thin-film memory and 4 megabytes of core memory. NASA acquired the only two 360/95s ever built. The console of the Model 95, for which no Functional Characteristics manuals exist, was identical to that of the 360/91.

First internet connected server

In 1971

UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California ...

used an IBM 360/91 to provide 'production computing services' to

ARPANET The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...

described in the Paper 'A SERVER HOST SYSTEM ON THE ARPANET' by Robert T. Braden. The services described include job submittal, a "mailbox" system and FTP (file transfer protocol).

In popular culture

There is a Model 91 Panel that is currently on display at the Living Computer Museum in

Seattle, Washington Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest region ...

that was borrowed and featured in the movie ''Tomorrowland'' (2015).

References

External links

IBM System/360 Model 91 Functional Characteristics

{{DEFAULTSORT:IBM System 360 Model 91 Computing platforms System/360 Model 91