IBM mainframe
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An IBM mainframe is a large, high performance computer made by International Business Machines (IBM). Mainframe computers traditionally are "expensive,"Template:Ref individually physically largeTemplate:Ref, and have high transaction processing and I/O performance, but are not as expensive and high performanceTemplate:Ref as supercomputers.
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History
From 1952 into the late 1960s, IBM manufactured and marketed several large computer models, known as the IBM 700/7000 series. The 700s were based on vacuum tubes, while the later 7000s used transistors. These machines established IBM's dominance in electronic data processing. IBM had two model categories: one (701, 704, 709, 7090, 7040) for engineering and scientific use, and one (702, 705, 7080, 7070, 7010) for commercial or data processing use. IBM initially sold its computers without any software, expecting customers to write their own; and programs were manually initiated, one at a time. This followed the model IBM had earlier established with their unit record equipment. Later IBM provided compilers for the newly developed higher-level programming languages Fortran and Cobol. The need to make the most efficient use of these multi-million dollar machines led to the introduction of simple operating systems, or job monitors. The two categories, scientific and commercial, generally used common peripherals but had completely different instruction sets, and there were incompatibilities even within each category. As software became more complex and important, the cost of supporting it on so many different designs became burdensome.
All that changed with the announcement of the System/360 (S/360) in April, 1964. The System/360 was a single series of compatible models for both commercial and scientific use. The number "360" suggested a "360 degree," or "all-around" computer system. System/360 incorporated features which had previously been present on only either the commercial line (such as decimal arithmetic and byte addressing) or the technical line (such as floating point arithmetic).Template:Ref The System/360 was also the first computer in wide use to include dedicated hardware provisions for the use of operating systems. Among these were supervisor and application mode programs and instructions, as well as built-in memory protection facilities.Template:Ref The new machine also had a larger address space than the older mainframes, 24 bits vs. a typical 18 bits. The System/360 later evolved into the System/370, the System/390, the zSeries, and the System z9.
Prior to System/360, IBM also sold computers smaller in scale, though still large and expensive by modern standards. These included:
- IBM 650 (vacuum tube era, decimal architecture, business and scientific)
- IBM RAMAC 305 (vacuum tube era, first computer with disk storage; see: Early IBM disk storage)
- IBM 1400 series (business data processing; very successful and many 1400 peripherals were used with the 360s)
- IBM 1620 (decimal architecture, engineering, scientific, and education)
IBM had difficulty getting customers to upgrade from the smaller machines to the mainframes because so much software had to be rewritten. The 7010 was introduced in 1962 as a mainframe-sized 1410. The smaller models in the System/360 line (e.g. the 360/30) were intended to replace the 1400 series while providing an easier upgrade path to the larger 360s. A desk size machine with a different instruction set, the IBM 1130, was released to address the 1620's niche. It was mostly programmed in Fortran, which was relatively easy to adapt to larger machines when necessary.
The second generation products were a mainstay of IBM's business and IBM continued to make them for several years after the introduction of the System/360. (Some IBM 7094s remained in service into the 1980s.) To smooth the transition from second generation to the new line, IBM used the 360's microprogramming capability to emulate the more popular older models. Thus 360/30s with this added cost feature could run 1401 programs and the larger 360/65s could run 7094 programs. To run old programs, the 360 had to be halted and restarted in emulation mode. Many customers kept using their old software and one of the features of the later System/370 was the ability to switch to emulation mode and back under operating system control.
Software
Operating systems
The primary operating systems in use on IBM mainframes include z/OS (which followed MVS and OS/390), z/VM (previously VM/CMS), z/VSE, z/TPF, and Linux on zSeries. A few systems still run MUSIC/SP, another operating system. Previous operating systems for the System/360 family and its successors included OS/360 (with PCP, MFT, and MVT), BOS, TOS, DOS, and SVS. There are software-based emulators for the System/370, System/390, zSeries, and System z9 hardware, including FLEX-ES and the freely available Hercules emulator which runs under Linux and Microsoft Windows. The original OS/360 and early MVS and VM/CMS versions have been released for free use.
Middleware
IBM mainframes run all the major enterprise transaction processing environments and databases, including CICS, IMS, WebSphere Application Server, DB2, and Oracle. In many cases these software subsystems can run on more than one mainframe operating system.
See also
References
- Prasad, Nallur (1994). IBM Mainframes: Architecture and Design, 2nd ed. McGraw-Hill Osborne Media. ISBN 0070506914.Template:Ref
External links
Notes
- Template:Note The acquisition price of one mainframe is higher than, say, one PC. However, that's a bit like saying the acquisition price of a train freight car is higher than the price of a bicycle basket. Both can move goods, but there the similarity ends, and the costs depend almost entirely on the tasks required of them. Mainframes reduce labor costs, software costs, and costs of outage, among other costs, because they are systems designed to achieve significant economies of scale.
- Template:Note Nowadays, because mainframes consolidate scores or even hundreds of otherwise individual servers, they consume less electricity and occupy less space than equivalent workloads executing on individual servers. Most 21st century data centers require much more space for distributed servers than for mainframes.
- Template:Note In single computational task terms. Weather modeling, protein folding analysis, nuclear explosion simulation, digital cinematography, and structural engineering analysis are examples of computational problems better suited to supercomputers. Mainframes are optimized for business transaction processing and large online database management, among other tasks.
- Template:Note Some of the arithmetic units and addressing features were optional on some models of the System/360. However, models were upward compatible and most were also downward compatible.
- Template:Note Hardware memory protection was provided to protect the operating system from the user programs (tasks) and the user tasks from each other.
- Template:Note Now dated. For details on the significant 64-bit architectural changes, refer to IBM technical publications (see z/Architecture).