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IBM System/360 Model 85

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This is an old revision of this page, as edited by Guy Harris (talk | contribs) at 03:17, 24 November 2016 ("It's possible" that Pugh etc. were mistaken, but if Pugh isn't a reliable source, we shouldn't use it. :-) The other reference just cites the same part of Pugh etc.'s book.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

IBM System/360 Model 85.
View of system console.
The left side has a
Microfiche Document Viewer

The IBM System/360 Model 85 was a high end system that was introduced in January, 1968, with many advanced features. IBM built only about 30 360/85 systems[1] because of "a recession in progress."

Models

The four offered models of the 360/85[2] were: I85 (512K), J85 (1M), K85 (2M) and L85 (4M), configured with 2 2365 Processor Storage units, 4 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 interleaving while the others provide four-way interleaving of memory access.

Advanced/special features

  • The system console was L-shaped: one leg was the "Main Control Panel, including a CRT, and the other leg included 2 screens: "Microfiche Document Viewer" and "Indicator Viewer."[2]: p.8 
  • Memory Cache - depending on the model and the situation, "the effective system storage cycle becomes one-third to one-fourth of the actual main storage cycle."[2]: p.5 
  • enhanced floating point - IBM offered extended-precision 128-bit quadruple-precision floating point on the 360/85[3]

Emulation

The 360/85, with the use of an emulator program and special instructions, permits running 709, 7040, 7044, 7094 and 7094 II programs.[2]: p.9 

Gateway to the future

The 360/85 used microcode to control instruction execution,[4] unlike the completely-hardwired 360/75 and 360/91; the high-end models of System/370 were also microcoded. Some describe the 360/85 as a bridge to the 370/165.[5]

See also

References

  1. ^ 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. ^ a b c d "IBM System/360 Model 85 Functional Characteristics" (PDF). IBM. June 1968. A22-6916-1.
  3. ^ and other high-end 360 models; IBM Floating Point Architecture
  4. ^ Robert L. Asenhurst. Foundations of Microprogramming. p. 34. ISBN 1483215873.
  5. ^ Jon Elson (December 5, 2014). "IBM 360/85 vs. 370/165". Newsgroup: alt.folklore.computers.
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