IBM mainframe

IBM mainframes are large computer systems produced by

From 1952 into the late 1960s, IBM manufactured and marketed several large computer models, known as the

IBM initially sold its computers without any software, expecting customers to write their own; programs were manually initiated, one at a time. Later, IBM provided

Prior to System/360, IBM also sold computers smaller in scale that were not considered mainframes, though they were still bulky and expensive by modern standards. These included:

• decimal architecture, drum memory
  , business and scientific)
• 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 later Systems 360 and 370 could emulate the 1400 machines. A desk-size machine with a different instruction set, the IBM 1130, was released concurrently with the System/360 to address the niche occupied by the 1620. It used the same EBCDIC character encoding as the 360 and was mostly programmed in Fortran, which was relatively easy to adapt to larger machines when necessary.

IBM also introduced smaller machines after S/360. These included:

• IBM 1800
• IBM Series/1
• IBM 3790
• IBM 8100
• IBM System/3 (Introduced 96 column card)

IBM System/360

IBM announced the System/360 (S/360) line of mainframes in April 1964.^[4] 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 engineering and scientific line (such as floating-point arithmetic). 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. 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. Hardware memory protection was provided to protect the operating system from the user programs (tasks) and user tasks from each other. The new machine also had a larger address space than the older mainframes, 24 bits addressing 8-bit bytes vs. a typical 18 bits addressing 36-bit words.

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. To smooth the transition from the second generation to the new line, IBM used the 360's

Operating systems for the System/360 family included

The System/360 later evolved into the

The IBM Z family, introduced in 2000 with the z900, supports z/Architecture, which extends the architecture used by the System/390 mainframes to 64 bits.

Processor units

The different processors on current IBM mainframes are:

• CP,
  Central Processor
  : general-purpose processor
• IFL, Integrated Facility for Linux: dedicated to Linux OSes (optionally under z/VM)
• ICF, Integrated Coupling Facility: designed to support Parallel Sysplex operations
• SAP, System Assist Processor: designed to handle various system accounting, management, and
  I/O channel
  operations
• zAAP, System z Application Assist Processor: currently limited to run only Java and XML
  processing
• IPSec

These are essentially identical, but distinguished for software cost control: all but CP are slightly restricted[a] such they cannot be used to run arbitrary operating systems, and thus do not count in software licensing costs (which are typically based on the number of CPs).^[5] There are other supporting processors typically installed inside mainframes such as

Software to allow users to run "traditional" workloads on zIIPs and zAAPs was briefly marketed by Neon Enterprise Software as "zPrime" but was withdrawn from the market in 2011 after a lawsuit by IBM.[6]

Operating systems

The primary

Middleware

Current IBM mainframes run all the major enterprise

See also

• List of IBM products
• Amdahl Corporation
• IBM midrange computer
• IBM LinuxONE
• IBM Secure Service Container
• Input/Output Configuration Program

Notes

References

Further reading

• Bashe, Charles J.; et al. (1986). IBM's Early Computers. MIT.
  ISBN 0-262-02225-7
  .
• Prasad, Nallur and Savit, Jeffrey (1994). IBM Mainframes: Architecture and Design, 2nd ed. McGraw-Hill Osborne Media.
  ISBN 0-07-050691-4
  .
• Pugh, Emerson W.; et al. (1991). IBM's 360 and Early 370 Systems. MIT.
  ISBN 0-262-16123-0
  .

Wikimedia Commons has media related to IBM mainframe computers.

• Official IBM mainframe page (IBM Z)
• IBM Mainframe Resources & Forum
• IBM Archives: IBM Mainframes
• IBM Archives: IBM Mainframe Family tree & chronology
• IBM Archives: IBM Mainframe album