IBM System/360 Model 91

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IBM System/360 Model 91
IBM Logo 1967-1972.svg
360-91-panel.jpg
System/360 Model 91 Panel at the Goddard Space Flight Center
Developer IBM
Release dateJanuary 1966
Predecessor IBM 7090
Successor IBM S/360 Model 195

The IBM System/360 Model 91 was announced in 1964 as a competitor to the CDC 6600. [1] Functionally, the Model 91 ran like any other large-scale System/360, 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. [2] It ran OS/360 as its operating system. It was designed to handle high-speed data processing for scientific applications. This included space exploration, theoretical astronomy, sub-atomic physics and global weather forecasting. [3]

Contents

The first Model 91 was used at the NASA Goddard Space Flight Center 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, [3] 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 made heavy use of instruction pipelining [4] and was the first implementation of Tomasulo's algorithm.[ citation needed ] It was also one of the first computers to utilize multi-channel memory architecture.

Castells-Rufas et al. reported that the 360/91 used 74kW of power. [5]

Models

There were four models of the IBM System/360 Model 91. [6] 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. [7] 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." [8] [9]

Differences from standard System/360 behaviour

Because of the emphasis on speed, there were some minor differences in the system's behaviour: [10]

  1. Floating point divide results could differ in the least significant bit.
  2. Some exceptions were imprecise.
  3. The handling of floating point underflow and overflow was different, although arguably better.
  4. Memory stores could occur out of sequence. A memory barrier instruction was added to allow control of this where necessary.

IBM and NASA

Front Panel of the Model 91. Currently on display at the Living Computer Museum in Seattle, Washington. IBM Model 91 Front Panel.jpg
Front Panel of the Model 91. Currently on display at the Living Computer Museum in Seattle, Washington.

IBM had a long history with NASA including the use of IBM components on crewed space flights such as the IBM ASC-15 on Saturn 1, the IBM ASC-15B on the Titan Family, IBM GDC on Gemini, IBM LVDC on Saturn 1B/5, IBM System/4 Pi-EP on the MOL, and the IBM System/4 Pi-TC 1 on the Apollo Telescope Mount and Skylab. [11]

The Model 91 was shipped 9 months late to the Goddard Space Flight Center in October 1967 and did not begin regular operations until January 1968 after it passed the federal government operations testing. [7]

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. [12] [7] NASA acquired the only two 360/95s ever built. [12] [13] [7]

The console of the Model 95, for which no Functional Characteristics manuals exist, was identical to that of the 360/91. [9]

First internet connected server

In 1971, UCLA used an IBM 360/91 to provide "production computing services" to ARPANET. The services it provided included job submittal, a "mailbox" system and FTP. [14]

There is a Model 91 Panel that is currently on display at the Living Computer Museum in Seattle, Washington that was borrowed and featured in the movie Tomorrowland (2015).

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<span class="mw-page-title-main">IBM System/360 Model 50</span> Midrange IBM computer from 1960s

The IBM System/360 Model 50 is a member of the IBM System/360 family of computers. The Model 50 was announced in April 1964 with the other initial models of the family, and first shipped in August 1965 to the Bank of America.

<span class="mw-page-title-main">IBM System/360 Model 65</span> IBM computer model from 1960s

The IBM System/360 Model 65 is a member of the IBM System/360 family of computers. It was announced April 1965, and replaced two models, the Model 60 and Model 62, announced one year prior but never shipped. It was discontinued in March 1974.

<span class="mw-page-title-main">IBM System/360 Model 85</span> High-end IBM computer model from late 1960s

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The IBM 2395 Processor Storage is a memory storage unit that was a component of the IBM System/360 Model 91 and Model 95.

<span class="mw-page-title-main">IBM System/390</span> Line of mainframe computers

The IBM System/390 is a discontinued mainframe product family implementing ESA/390, the fifth generation of the System/360 instruction set architecture. The first computers to use the ESA/390 were the Enterprise System/9000 (ES/9000) family, which were introduced in 1990. These were followed by the 9672, Multiprise, and Integrated Server families of System/390 in 1994–1999, using CMOS microprocessors. The ESA/390 succeeded ESA/370, used in the Enhanced 3090 and 4381 "E" models, and the System/370 architecture last used in the IBM 9370 low-end mainframe. ESA/390 was succeeded by the 64-bit z/Architecture in 2000.

<span class="mw-page-title-main">IBM System/360 Model 195</span> High-end IBM computer model from 1970s

The IBM System/360 Model 195 is a discontinued IBM computer introduced on August 20, 1969. The Model 195 was a reimplementation of the IBM System/360 Model 91 design using monolithic integrated circuits. It offers "an internal processing speed about twice as fast as the Model 85, the next most powerful System/360". The Model 195 was discontinued on February 9, 1977, the same date as the System/370 Model 195.

References

  1. ↑ "IBM Advanced Computing Systems -- Timeline". people.cs.clemson.edu.
  2. ↑ "Out of Order Execution of Computer Instructions".
  3. 1 2 "IBM Archives: System/360 Model 91". IBM. 23 January 2003. Archived from the original on 2023-09-23. Retrieved 28 June 2016.
  4. ↑ "IBM System/360, Model 91 (console)". ed-thelen.org. Retrieved 29 June 2016.
  5. ↑ Castells-Rufas, David; Saa-Garriga, Albert; Carrabina, Jordi (January 2016). Energy Efficiency of Many-Soft-Core Processors. International Workshop on High Performance Energy Efficient Embedded Systems (HIP3ES 2016). Prague, Czech Republic. arXiv: 1601.07133 . doi:10.13140/RG.2.1.1276.5042. S2CID   14349505.
  6. ↑ William H. Blair. "The 360/91 and associated machines". hercules-390 (Mailing list).
  7. 1 2 3 4 Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and early 370 systems. Cambridge, Mass.: MIT Press. p. 394. ISBN   0262161230.
  8. ↑ gah. "The 360/91 and associated machines". hercules-390 (Mailing list).
  9. 1 2 William H. Blair. "The 360/91 and associated machines". hercules-390 (Mailing list).
  10. ↑ IBM, Systems Reference Library. "IBM System/360 Model 91 Functional Characteristics" (PDF). Bitsavers.org. IBM. Retrieved 31 May 2024.
  11. ↑ "Spaceborne Digital Computer Systems" (PDF). NASA Government Archive. National Aeronautics and Space Administration. March 1971. Retrieved 29 June 2016.
  12. 1 2 "IBM Archives: System/360 Model 95". IBM. 23 January 2003. Archived from the original on 2023-07-20.
  13. ↑ Chuck Boyer (April 2004). The 360 Revolution (PDF). IBM. One model of the System/360, the 95, was built especially for NASA, and only two units were made. One went to Goddard Space Flight Center in Maryland; the other to the Goddard Institute for Space Studies on upper Broadway in Manhattan.
  14. ↑ Braden, Robert T. (1977). "A server host system on the ARPANET". Proceedings of the fifth symposium on Data communications - SIGCOMM '77. Snowbird, Utah, United States: ACM Press. pp. 4.1–4.9. doi: 10.1145/800103.803337 .

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