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'''Minicomputer''' (colloquially, '''mini''') is a largely obsolete term for a class of multi-user [[computer]]s which make up the middle range of the computing spectrum, in between the largest [[multi-user systems]] (traditionally, [[mainframe computer]]s) and the smallest single-user systems ([[microcomputer]]s or [[personal computers]]). More modern terms for such machines include [[IBM midrange computer|midrange systems]] (common in [[IBM]] parlance), [[computer workstation|workstation]]s (common in [[Sun Microsystems]] and general [[Unix|UNIX]]/[[Linux]] parlance), and [[Server (computing)|server]]s.
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===1960s: Origin; 1970s: Market entrenchment===
The term “minicomputer” evolved in the [[1960s]] to describe the “small” third generation computers that became possible with the use of [[transistor]] and [[core memory]] technologies. The term came in fashion about the same time as the [[miniskirt]] and [[mini]] cars. They usually took up one or a few cabinets the size of a large refrigerator or two, compared with [[mainframe computer|mainframes]] that would usually fill a room. The first successful minicomputer was [[Digital Equipment Corporation]]’s 12-bit [[PDP-8]], which cost from [[United States dollar|US$]]16,000 upwards when launched in [[1964]]. The important precursors of the PDP-8 include the PDP-5, [[LINC]], the [[TX-0]], the [[TX-2]], and the [[PDP-1]].
The [[7400 series]] of [[transistor-transistor logic|TTL]] [[integrated circuit]]s started appearing in minicomputers in the late [[1960]]s. The 74181 [[arithmetic-logic unit]] (ALU) was commonly used in the [[central processing unit|CPU]] data paths. Each 74181 had a bus width of four bits, hence the popularity of ''bit-slice'' architecture. The 7400 series offered data-selectors, [[multiplexer]]s, three-state buffers, memories, etc. in [[dual in-line package]]s with one-tenth inch spacing, making major system components and architecture evident to the naked eye. (Starting in the [[1980]]s, many minicomputers used [[VLSI]] circuits (Very Large Scale Integration), often making the hardware organization much less apparent.)
As microcomputers developed in the [[1970s]] and [[1980s|80s]], minicomputers filled the mid-range area between low powered microcomputers and high capacity mainframes. At the time microcomputers were single-user, relatively simple machines running simple program-launcher operating systems like [[CPM operating system|CP/M]] or [[MS-DOS]], while minis were much more powerful systems that ran full multi-user, multitasking operating systems like [[OpenVMS|VMS]] and [[Unix]], often with [[time-sharing|timesharing]] versions of [[BASIC]] for application development ([[MAI Basic 4]] systems being very popular in that regard). The classical mini was a [[16-bit]] computer, while the emerging higher performance [[32-bit]] minis were often referred to as [[supermini]]s.
===Mid-1980s, 1990s: The minis give way to the micros===
The decline of the minis happened due to the lower cost of microprocessor based [[computer hardware|hardware]], the emergence of inexpensive and easily deployable [[local area network]] systems, and the desire of end-users to be less reliant on inflexible minicomputer manufacturers and IT departments/“data centers”—with the result that minicomputers and [[dumb terminal]]s were replaced by networked [[workstation]]s and [[IBM PC compatible|PC]]s in the latter half of the [[1980s]].
During the [[1990s]] the change from minicomputers to inexpensive PC networks was cemented by the development of several versions of [[Unix]] to run on the [[Intel]] [[x86]] microprocessor [[computer architecture|architecture]], including [[Solaris Operating Environment|Solaris]], [[Linux]], [[FreeBSD]], [[NetBSD]] and [[OpenBSD]]. Also, the Microsoft Windows series of operating systems now includes server versions that support preemptive multitasking and other features required for servers, beginning with [[Windows NT]].
As [[microprocessor]]s have become more powerful, [[central processing unit|CPUs]] built up from multiple components—once the distinguishing feature differentiating mainframes and midrange systems from microcomputers—have become increasingly obsolete, even in the largest [[mainframe computer]]s.
[[Digital Equipment Corporation]] was the leading minicomputer manufacturer, at one time the 2nd largest computer company after [[IBM]]. But as the minicomputer declined in the face of generic UNIX servers and Intel based PCs, not only DEC, but almost every other minicomputer company including [[Data General]], [[Prime Computer|Prime]], [[Computervision]], [[Honeywell]] and [[Wang Computer]], many based in [[New England]] also collapsed. DEC was sold to Compaq in 1998.
===The minicomputer’s industrial impact and heritage===
Several pioneering computer companies first built minicomputers, such as DEC, [[Data General]], and [[Hewlett-Packard|Hewlett-Packard (HP)]] (who now refers to its HP3000 minicomputers as “servers” rather than “minicomputers”). And although today’s PCs and servers are clearly microcomputers physically, architecturally their CPUs and operating systems have evolved largely by integrating features from minicomputers.
In the software context, the relatively simple OSs for early minicomputers were usually inspired by minicomputer OSs (such as CP/M by RSTS) and multiuser OSs of today are often either inspired by or directly descended from minicomputer OSs (UNIX was originally a minicomputer OS)
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Today at the turn of the millennium few minicomputers are still in use, having been overtaken by Fourth Generation computers built using a more robust version of the [[microprocessor]] technology that is used in personal computers. These are referred to as “[[Server (computing)|server]]s,” taking the name from the server software that they run (typically file server and back-end database software, including [[email]] and [[web server]] software).
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==List of some notable minicomputers==
*[[Control Data]]’s [[CDC 160A]] and [[CDC 1700]]
*[[Digital Equipment Corporation|DEC]] [[Programmed Data Processor|PDP]] and [[VAX]] series
*[[Data General]] [[Data General Nova|Nova]]
*[[Hewlett-Packard]] [[HP3000]] series
*[[Honeywell]]-[[Groupe Bull|Bull]] [[Level 6/DPS 6/DPS 6000]] series
*[[IBM]] [[IBM midrange computer|midrange computer]]s
*[[Norsk Data]] Nord-1, Nord-10, and Nord-100
*[[Prime Computer]] Prime 50 series
*[[Scientific Data Systems|SDS]] SDS-92
*[[Wang Laboratories]] 2200 and VS series
==See also==
*''[[The Soul of a New Machine]]'' - about the development of Data General’s Eclipse/MV minicomputers in the early 1980s
*[[Charles Babbage Institute]]
*[[History of computing hardware (1960s-present)]]
*[[Supermini]]
[[Category:Minicomputers|*Minicomputer]]
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