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 IBM System/360 Model 50 console and CPU with front panel | |
| Manufacturer | International Business Machines Corporation (IBM) |
|---|---|
| Product family | System/360 |
| Release date | April 7, 1964 |
| Discontinued | March 15, 1977 [1] |
| Memory | 64–512 KB Core |
The IBM System/360 Model 50 is a member of the IBM System/360 family of computers. The Model 50 was announced in April 1964 with the other initial models of the family, and first shipped in August 1965 to the Bank of America. [2]
There are four models of the 360/50. [3] : page 5 They vary by the amount of core memory with which the system is offered. The F50, or 2050F is equipped with 65,536 bytes, the G50 has 131,072 bytes, the H50 262,144 bytes, and the I50 524,288 bytes. [3] The system can also attach IBM 2361 Large Capacity Storage (LCS) modules which provide up to 8,388,608 bytes of additional storage, however with a considerably slower memory cycle time of 8 microseconds compared to the 2 microseconds of processor storage. [3]
The system has a CPU cycle time of 500 nanoseconds, 25% faster than the Model 40 and 40% slower than the Model 65. Processor storage is magnetic core memory that transfers four bytes per 2 microsecond cycle. It has "protected" and "local" core storage for registers and internal buffers with cycle times of 200 and 500 nanoseconds respectively.
The Model 50 implements the complete System/360 "universal instruction set" architecture, including floating-point, decimal, and character operations as standard features. The "direct control" instructions are an optional feature. Optional logic, microcode and software providing compatibility with either the IBM 1410/7010 or 7070/7074 systems is available.
An IBM 1052 printer/keyboard for use as an operator's console is optional. The I/O options include one channel-to-channel adapter (CTCA) and up to three selector channels. A multiplexer channel for attachment of slow-speed devices is standard on all models. The F50 has 64 subchannels, so it can attach up to 64 slow-speed devices on its multiplexer channel. The other models have 128 subchannels. This can optionally increase to 256 subchannels on the H50 and I50. [3]
The Model 50 uses a 90 bit (or 85 bit, depending on definition) "horizontal microcode" instruction format, with each word containing 15 (or 25) separate fields. [4] There are 2816 words of microcode storage. [5]
Read-only control storage for microcode employs "balanced capacitor technology" (BCROS) with a cycle time of 500 nanoseconds, designed by Anthony Proudman in IBM's Hursley laboratory and implemented by Fernando "Fred" Neves. This technology uses two capacitors to represent each bit.
It was possible to choose DOS/360, OS/360 MFT (Multi-programming with a Fixed number of Tasks), or OS/360 MVT (Multi-programming with a Variable number of Tasks) as the operating system of an IBM System/360 Model 50. Few chose MVT. [6]
The choice of operating system for the System/360 Model 50 was based primarily on the amount of main storage. The F50, with 65,536 bytes of main storage, can not run OS/MFT, which requires a minimum of 131,072 bytes of main storage. [7] DOS/360 has a minimum of 16,384 bytes of main storage. [8]
Systems with 131,072 or more bytes of main storage could run OS/360. Although 360/50 systems equipped with 1 MB or more [9] could and did run MVT [10] [11] one IBMer described this as "[getting] blood out of the turnip", and noted that "most didn't run MVT". [6]
Reasons for a 360/50 site to run MFT [12] rather than MVT were:
IBM advertised time-sharing capability [17] by featuring what originally was known as CALL/360 [18] (note the 'SLASH' - which was retained in the name of its successor) and later [19] was named CALL/OS. CALL/OS featured its own versions of BASIC [20] as well as FORTRAN IV [21] and PL/I, [22] [23] rather than the versions implemented by the MFT/MVT compilers known as FORTRAN G, FORTRAN H and PL/I F. CALL/OS is sometimes referred to as "CALL-OS". [24]
Installations with a larger model of the System/360 family sometimes ran/retained the combination of MFT and CALL/OS, [21] rather than switch to MVT, a pre-requisite for TSO, [25] after an upgrade.
IBM mainframes are large computer systems produced by IBM since 1952. During the 1960s and 1970s, IBM dominated the computer market with the 7000 series and the later System/360, followed by the System/370. Current mainframe computers in IBM's line of business computers are developments of the basic design of the System/360.
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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 applications and a complete range of applications from small to large. The design distinguished between architecture and implementation, allowing IBM to release a suite of compatible designs at different prices. All but the only partially compatible Model 44 and the most expensive systems use microcode to implement the instruction set, featuring 8-bit byte addressing and binary, decimal and hexadecimal floating-point calculations.
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 for customers; this, plus improved performance, were the dominant themes of the product announcement. In September 1990, the System/370 line was replaced with the System/390.
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Operating System/Virtual Storage 1, or OS/VS1, is a discontinued IBM mainframe computer operating system designed to be run on IBM System/370 hardware. It was the successor to the Multiprogramming with a Fixed number of Tasks (MFT) option of System/360's operating system OS/360. OS/VS1, in comparison to its predecessor, supported virtual memory. OS/VS1 was generally available during the 1970s and 1980s, and it is no longer supported by IBM.
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System Generation (SysGen) is a two-stage process for installing or updating OS/360, OS/VS1, OS/VS2 (SVS), OS/VS2 (MVS) and chargeable systems derived from them. There are similar processes for, e.g., DOS/360, which this article does not cover. Also, some of the details have changed between releases of OS/360 and many details do not carry over to later systems.
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Your point is well taken. But most didn't run MVT, and many that did had LCS (Large Capacity Storage). MVT was not very popular. Nonetheless, I ran a system that ran MVT just fine with only 256MB; maximum REGION size was 114MB, which was perfectly fine for the workload. I suspect that if MVT was being used on a /65 or /75, then 512KB was installed. But, there were a lot of folks that ran MVT on a /50 with 384KB. We got blood out of the turnip back in those days.
Disk and Tape Operating Systems are comprehensive sets of language translators and service programs operating under the supervisory coordination of an integrated control program. They require an IBM System/360 with at least 16K bytes of main storage.
We had to revert to MFT to get a 98K partition, plus a reader and writer.
The minimum main storage is 262,144 (256K) bytes
... a happy timeshare user .. 'This man is sharing a $2 million computer.'
The program (Dissim) is written in Call-os Fortran IV and is now in use on an IBM 360/75 with teletypewriter remote facilities.
Can you or any of your readers direct me to a version of Adventure written in standard Basic, Fortran, or IBM Call-OS PL/I?
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