IBM System/360 Model 85

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

• IBM System/360 Model 20
• IBM System/360 Model 22
• IBM System/360 Model 25
• IBM System/360 Model 30
• IBM System/360 Model 40
• IBM System/360 Model 44
• IBM System/360 Model 50
• IBM System/360 Model 65
• IBM System/360 Model 67
• IBM System/360 Model 91

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. "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.