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. IBM built only about 30 360/85 systemsbut 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." because of "a recession in progress".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
Models The four models of the 360/85 are: I85 (512K), J85 (1M), K85 (2M) and L85 (4M), configured with two IBM 2365 Processor Storage units, four 2365 magnetic-core memory 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 two screens: "Microfiche Document Viewer" and "Indicator Viewer." 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." 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 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 (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, with the use of an emulator program permits running 709, 7040, 7044, 7094 and 7094 II programs.
Gateway to the future In some respects, the System/360 Model 85 provided a glimpse into the future System/370 product line, 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, 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.
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