IBM System/360 Model 40

History

On April 7, 1964, IBM announced the IBM System/360, to be available in six models. The 360/40 was first delivered in April 1965.

The 360/30 and the 360/40 were the two largest revenue producing System/360 models, accounting for over half of the units sold.

Models

Five models of the 360/40 were offered. The D40, E40, F40, G40 and H40 were configured with 16K, 32K, 64K, 128K and 256K of core memory and correspondingly 16, 32, 64, 128 and 128 not a typo: the physical limit seemed to be 224; see p. 17 of the Model 30 Functional Characteristics multiplexer subchannels.

The H40 occupied "more floor space than the other models."

Configuration

Microprogramming

Like most System/360 models the Model 40 is microprogrammed. The microcode is stored in transformer read-only storage (TROS), organized as up to 8192 words of 56 bits each. Standard microcode consists of up to 4096 words. The additional 4096 words are used for the 1401 or 1410 compatibility feature.

IBM 1400 series emulation

With the additional Compatibility Feature hardware and Compatibility Support software under DOS/360, the IBM 1401/1440/1460 object programs can be run in the emulation mode, with little or no reprogramming.

Other

Although the cover of IBM's MVT Guide indicates that even a 360/40 could run MVT, the IBM operating system used was usually the realistically sized DOS/360, because all but one model of the 360/40 had less than MVT's minimum memory requirements of 256KB.

The IBM System/360 Model 40 was developed at IBM Hursley and manufactured at IBM's facilities in Poughkeepsie, New York, Mainz, Germany; and Fujisawa, Japan.

A modified Model 40 ran CP-40, the ancestor of CP/CMS, which in turn was the progenitor of the VM line.

Notes

References

References

1. (23 January 2003). "IBM Archives: System/360 Model 40".
2. [https://www.flickr.com/photos/dabcanboulet/131523955/ IBM System/360 model 40] (Flickr from Yahoo!)
3. Emerson W. Pugh. (1995). "Building IBM: Shaping an Industry and Its Technology". MIT Press.
4. (2015). "From Mainframes to Smartphones". [[Harvard University Press]].
5. Fortune magazine, Sept. 1966, p.118
6. (23 January 2003). "IBM Archives: System/360 Dates and characteristics".
7. (1991). "IBM's 360 and early 370 systems". MIT Press.
8. (1969). "Computer Usage Essentials". McGraw-Hill.
9. (August 1971). "IBM System/360 Model 40 Functional Characteristics".
10. "IBM System/360 Model 40 Operating Techniques". IBM.
11. (1970). "IBM Field Engineering Manual of Instruction: System/360 model 40 Functional Units".
12. (February 1969). "IBM System/360 Disk Operating System 1401/1440/1460 Emulator Programs: Compatibility Support/30 & /40". IBM.
13. (August 1974). "IBM System/360 Operating System: MVT Guide OS Release 21.7". IBM.
14. (April 1973). "IBM System/360 Operating System: Storage Estimates OS Release 21.7". IBM.
15. Ray Saunders. "MVS... And Before OS/360 ?".
16. Nicholas Enticknap. "Editorial". Resurrection: The Bulletin of the Computer Conservation Society.
17. (23 January 2003). "IBM Archives: Fujisawa plant".