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 announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...

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 ...

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." *

CPU cache A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, whi ...

, 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 In computing, an emulator is Computer hardware, 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 sof ...

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 range of IBM mainframe computers announced as the successors to the IBM System/360, System/360 family on June 30, 1970. The series mostly maintains backward compatibility with the S/360, allowing an easy migrati ...

product line, particularly the

IBM System/370 Model 165 The IBM System/370 Model 165 (and the Model 155) were jointly announced June 30, 1970 as "designed for ... the Seventies." That same day IBM announced the 370/195. They were the first three models of the IBM System/370 line of computers. Since ...

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 In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. It consists of a set of hardware-level instructions ...

to control instruction execution, unlike the completely- hardwired 360/75 and 360/91; the high-end models of

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

References

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