Minicomputer
Minicomputer (colloquially,
mini) is a largely obsolete term for a class of multi-user
computers which make up the middle range of the computing spectrum, in between the largest multi-user systems (traditionally,
mainframe computers) and the smallest single-user systems (
microcomputers or
personal computers). More modern terms for such machines include
midrange systems (common in
IBM parlance),
workstations (common in
Sun Microsystems and general
UNIX/
Linux parlance), and
servers.
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
mainframes that would usually fill a room. The first successful minicomputer was
Digital Equipment Corporation's 12-bit
PDP-8, which cost from
US$16,000 upwards when launched in
1964.
The
7400 series of
TTL integrated circuits started appearing in minicomputers in the late
1960s. The 74181
arithmetic-logic unit (ALU) was commonly used in the
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,
multiplexers, three-state buffers, memories, etc. in
dual in-line packages with one-tenth inch spacing, making major system components and architecture evident to the naked eye. (Starting in the
1980s, many minicomputers used
VLSI circuits (Very Large Scale Integration), often making the hardware organization much less apparent.)
As microcomputers developed in the
1970s and
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
CP/M or
MS-DOS, while minis were much more powerful systems that ran full multi-user, multitasking operating systems like
VMS and
Unix. The classical mini was a
16-bit computer, while the emerging higher performance
32-bit minis were often referred to as
superminis.
Mid-1980s, 1990s: The minis give way to the micros
The decline of the minis happened due to the lower cost of microprocessor based
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 terminals were replaced by networked
workstations and
PCs 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
architecture, including
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
microprocessors have become more powerful,
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 computers.
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,
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 (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 first microcomputer operating system,
CP/M was an implementation of a DEC PDP-11 operating system for the 8080 and Z80 processors. DOS, which gives its command line to Windows, was an unauthorized port / redesign of CP/M for the 8086. The
Windows NT operating system was headed by a designer from
DEC responsible for the
VMS OS for the
VAX minicomputer range in the 1970s, and adopted features from UNIX which ran largely on minicomputers.
microprocessor technology that is used in personal computers. These are referred to as "
servers", taking the name from the server software that they run (typically file server and back-end database software, including
email and
web server software).
*
Control Data's
CDC 160A *
DEC PDP and
VAX series
*
Data General Nova*
Hewlett-Packard HP3000 series
*
Honeywell-
Bull Level 6/DPS 6/DPS 6000 series
*
IBM midrange computers
*
Norsk Data Nord-1, Nord-10, and Nord-100
*
Prime Computer Prime 50 series
*
SDS SDS-92
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
