IBM System/360 Model 40
| Company type | Computer model |
|---|---|
| Industry | Computer hardware |
| Predecessor | IBM System/360 Model 30 |
| Founded | April 7, 1964 |
| Defunct | October 7, 1977 |
| Headquarters | Poughkeepsie, New York; Mainz, Germany; Fujisawa, Japan , United States; Germany; Japan |
| Products | Mid-tier mainframe computer in IBM System/360 series |
The IBM System/360 Model 40 represented a mid-tier option within the IBM System/360 series. It was announced on April 7, 1964, began shipping in 1965, and remained available until its discontinuation on October 7, 1977.
History
On April 7, 1964, IBM launched the System/360 family, which initially included six distinct models. The delivery of the Model 40 started in April 1965.
Within the System/360 range, the Model 30 and Model 40 were the most commercially successful, together accounting for more than half of total sales. The Model 30 alone made up roughly 36% of units sold, while the Model 40 contributed about 22.6%, combining to nearly 59% of the series' market share.
Models
The System/360 Model 40 was available in five variants: D40, E40, F40, G40, and H40. These differed by core memory capacity—16K, 32K, 64K, 128K, and 256K respectively—and were equipped with multiplexer subchannels numbering 16, 32, 64, 128, and again 128.[NB 1] Notably, the H40 model demanded a larger physical footprint compared to its counterparts.[1]
Configuration
| Standard early configuration for a Model 40 system:[2] | |
|---|---|
| Model 40 processor | IBM 2040 CPU *128 KB memory *storage protection feature *full universal instruction set *one multiplexor channel *two selector channels *interval timer |
| Operator console | IBM 1052 Typewriter-Keyboard (commonly assigned to address hexadecimal 009) |
| Unit record device | IBM 1442 Card Reader-Punch (address 00A) or IBM 2540 Reader-Punch (addresses 00C & 00D) |
| Line printer | IBM 1443 Printer (address 00B) or IBM 1403 Printer (address 00E) |
| Disk storage | IBM 2311 Magnetic Disk Drives (units numbered 190 & 191) or IBM 2314 Direct Access Storage Facility |
| Tape storage | IBM 2401 Magnetic Tape Drives (180 & 181 for seven-track; units 182 &183 for nine-track) |
| Telecommunications controller | IBM 2701 Communication Controller (utilized in telecommunication setups) |
Microprogramming
As with most models in the System/360 line, the Model 40 employed microprogramming. Its microcode resided in transformer read-only storage (TROS), capable of holding up to 8192 words of 56 bits each. The standard microcode required up to 4096 words; an additional block of equal size was reserved for IBM 1401/1410 compatibility functionality.[3]
IBM 1400 series emulation
Equipped with supplementary Compatibility Feature hardware and software under DOS/360, the Model 40 could execute IBM 1401/1440/1460 object code through emulation with minimal modifications necessary.Cite error: The opening <ref> tag is malformed or has a bad name
Other
Although IBM's MVT Guide suggested that even a System/360 Model 40 could operate MVT, in practice the more commonly used operating system was DOS/360, since all but one variant of the Model 40 fell short of MVT's minimum memory requirement of 256KB.
Development of the IBM System/360 Model 40 took place at IBM Hursley, while manufacturing occurred at IBM plants located in Poughkeepsie, New York; Mainz, Germany; and Fujisawa, Japan.
A customized version of the Model 40 also ran CP-40, which served as the predecessor to CP/CMS and laid the groundwork for the VM series.
References
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