The IBM System/360 Model 85 is a high-end member of the

System/360 The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applica ...

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 systems because of "a recession in progress".

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 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 In computing, interleaved memory is a design which compensates for the relatively slow speed of dynamic random-access memory (DRAM) or core memory, by spreading memory addresses evenly across memory banks. That way, contiguous memory reads and w ...

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." * 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." The memory 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 In computing, an emulator is hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run software or use pe ...

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 The IBM System/370 (S/370) is a model range of IBM mainframe computers announced on June 30, 1970, as the successors to the System/360 family. The series mostly maintains backward compatibility with the S/360, allowing an easy migration path ...

product line (particularly the

370 Model 165 37 may refer to: * 37 (number), the natural number following 36 and preceding 38 Years * 37 BC * AD 37 * 1937 * 2037 Other uses * ''37'' (album), by King Never, 2013 * ''37'' (film), a 2016 film about the murder of Kitty Genovese * 37 (MBTA b ...

) - 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 uses

microcode In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a la ...

to control instruction execution, unlike the completely-

hardwired Hardwire or hardwired may refer to: * Electrical wiring *Hardwired control unit, a part of a computer's central processing unit *In computer programming, a kludge to temporarily or quickly fix a problem * Wired communication In arts and entertai ...

360/75 and 360/91; the high-end models of

also use horizontal microcode, except the IBM System/370 model 195.

References

{{DEFAULTSORT:IBM System 360 Model 85 System/360 Model 85