Jump to content

IBM System/360 Model 85

From Wikipedia, the free encyclopedia
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.
IBM System/360 Model 85
IBM System/360 Model 85.
View of system console.
The left side has a
Microfiche Document Viewer
ManufacturerInternational Business Machines Corporation (IBM)
Product familySystem/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]

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

  • The system console is L-shaped: one leg is the Main Control Panel, including a CRT, and the other leg includes 2 screens: "Microfiche Document Viewer" and "Indicator Viewer."[4]: p.8 
  • CPU cache, which IBM termed "high-speed buffer storage" - depending on the model and the situation, "the effective system storage cycle becomes one-third to one-fourth of the actual main storage cycle."[4]: p.5  The cache is high-speed, static buffer memory situated between the CPU and main system memory ("Level 1" cache), available in 16 KB and 32 KB size options. The System/360 Model 85 is the first commercially available computer with cache memory.
  • Monolithic integrated circuits[5]
  • Enhanced floating point - The Model 85 comes with extended-precision 128-bit quadruple-precision floating point
  • The Model 85 has both Read-only and Writeable Control Storage[4]: p.14  (it is the second System/360 to have writeable control storage; the IBM System/360 Model 25 is the first to have rewriteable control storage; the 360/85 was introduced Jan. 30, 1968).

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. ^ a b 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. ^ a b c d e "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.
Retrieved from "https://en.wikipedia.org/w/index.php?title=IBM_System/360_Model_85&oldid=1285024478"