IBM System/360 Model 85
 | |
|
IBM System/360 Model 85. View of system console. The left side has a Microfiche Document Viewer | |
| Manufacturer | International Business Machines Corporation (IBM) |
|---|---|
| Product family | System/360 |
| Memory | 512 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, that was introduced in January, 1968. IBM only built 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 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 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
- 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."[4]:p.5
- enhanced floating point - IBM offered extended-precision 128-bit quadruple-precision floating point on the 360/85[5]
- 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, with the use of an emulator program and special instructions, permits running 709, 7040, 7044, 7094 and 7094 II programs.[4]:p.9
Gateway to the future
The 360/85 uses microcode to control instruction execution,[6] unlike the completely-hardwired 360/75 and 360/91; the high-end models of System/370 are also microcoded.
References
- ↑ 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.
- ↑ 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."
- ↑ 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 1960's through the mid-1980's, 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
- 1 2 3 4 5 "IBM System/360 Model 85 Functional Characteristics" (PDF). IBM. June 1968. A22-6916-1.
- ↑ and other high-end 360 models; IBM Floating Point Architecture
- ↑ Robert L. Asenhurst. Foundations of Microprogramming. p. 34. ISBN 1483215873.