IBM System/360 Model 85

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IBM System/360 Model 85
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IBM System/360 Model 85.
View of system console.
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ManufacturerInternational Business Machines Corporation (IBM)
Product family System/360
Memory512 K - 4 M Core

The IBM System/360 Model 85 is a high-end member of the System/360 family of computers, with many advanced features, and was announced in January 1968 and first shipped in December 1969. [1] IBM built only about 30 360/85 systems [1] [2] because of "a recession in progress". [3]

Contents

Models

The four models of the 360/85 [4] are: I85 (512K), J85 (1M), K85 (2M) and L85 (4M), configured with two IBM 2365 Processor Storage units, four 2365 units, an IBM 2385 Processor Storage unit Model 1 (=2M), or an IBM 2385 Processor Storage unit Model 2 (=4M) respectively. The I85 includes two-way interleaved memory while the others provide four-way interleaving of memory access.

Advanced/special features

Emulation

The 360/85, when equipped with the 709/7090/7094 Compatibility Feature, [6] with the use of an emulator program permits running 709, 7040, 7044, 7094 and 7094 II programs. [4] :p.9 [7]

Gateway to the future

In some respects, the System/360 Model 85 provided a glimpse into the future System/370 product line, [8] particularly the IBM System/370 Model 165 which IBM announced two years later (1970). It used the MST circuitry that was later used in the initial System/370 models, and introduced features such as 128-bit floating point arithmetic and block multiplexor channels that are also part of the System/370 architecture.

The 360/85 has a hardwired I-unit to fetch and decode instructions, but the E-unit uses microcode to control instruction execution, [9] unlike the completely-hardwired 360/75 and 360/91; the high-end models of System/370 also use horizontal microcode, except for the IBM System/370 Model 195. [10]

References

  1. 1 2 Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and Early 370 Systems. Cambridge: MIT Press. p. 419. ISBN   0-262-16123-0.
  2. but it was noted in http://hercules-390.yahoogroups.narkive.com/ritmdhO6/the-360-91-and-associated-machines that "a 360/85 was delivered from when a 91 was ordered until it was ready." This same source, after quoting from Pugh et al adds "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."
  3. The recession's most important effect regarding the high-end mainframes was a matter of less available government money, as noted in https://history.nasa.gov/SP-4221/ch7.htm ("CHAPTER 7: AEROSPACE RECESSION"). By contrast, the Bureau of Labor Statistics says "From the early 1960s through the mid-1980s, the outlook for growth in the computer manufacturing industry was, for most of the period, unusually optimistic." http://www.bls.gov/opub/mlr/1986/09/art2full.pdf
  4. 1 2 3 4 5 "IBM System/360 Model 85 Functional Characteristics" (PDF). IBM. June 1968. A22-6916-1.
  5. Conti; et al. (1968). "Structural aspects of the System/360 Model 85, I: General organization". IBM Systems Journal. 7 (1): 2–14. doi:10.1147/sj.71.0002. Its basic design includes monolithic circuits, very wide data paths, an 80-nanosecond internal buffer of at least 16K bytes, and a high-speed multiply feature.
  6. IBM System/360 Special Feature Description 709/7090/7094 Compatibility Feature for IBM System/360 Model 85 (First ed.), IBM, March 1969, GA27-2733-0
  7. Emulating the IBM 7094 on the IBM Models 85 and 165 using OS/360 Program Number for M/85: 360C-EU-734 Program Number for M/165: 360C-EU-740 OS Release 20 (Third ed.), IBM, November 1971, GC27-6951-2
  8. Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and Early 370 Systems. Cambridge: MIT Press. p. 479. ISBN   0-262-16123-0. In May 1968, during the course of contention over Model 85 architecture, which was intended to represent a first step toward NS architecture...
  9. Robert L. Asenhurst (2014-06-25). Foundations of Microprogramming. p. 34. ISBN   978-1483215877.
  10. "IBM Archives: System/370 Model 195". IBM. 23 January 2003. Archived from the original on 2023-07-29. Retrieved March 24, 2018.