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The Acorn System was a series of modular
microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (P ...
systems based on rack-mounted Eurocards developed by
Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England in 1978 by Hermann Hauser, Christopher Curry (businessman), Chris Curry and Andy Hopper. The company produced a number of computers during the 1980s with asso ...
from 1979 to 1982, aimed primarily at industrial and laboratory use, but also home enthusiasts. The experience gained in developing this modular system strongly influenced the design of Acorn's first all-in-one home computer, the
Acorn Atom The Acorn Atom is a home computer made by Acorn Computers Ltd from 1980 to 1982, when it was replaced by the BBC Micro. The BBC Micro began life as an upgrade to the Atom, originally known as the Proton. The Atom was a progression of the MOS T ...
, released in March 1980; and also much of the circuitry in its successor, the
BBC Micro The BBC Microcomputer System, or BBC Micro, is a family of microcomputers developed and manufactured by Acorn Computers in the early 1980s as part of the BBC's Computer Literacy Project. Launched in December 1981, it was showcased across severa ...
, first shown in late 1981. Acorn's final rack-based machine was the System 5, released in late 1982. The Eurocard business was then sold on to one of its principal resellers, Control Universal Ltd, which continued to develop various cards for industrial use based on the Acorn-standard bus during the 1980s, but ultimately went into
receivership In law, receivership is a situation in which an institution or enterprise is held by a receiver – a person "placed in the custodial responsibility for the property of others, including tangible and intangible assets and rights" – especia ...
in 1989.


Eurocards

Placing the two Eurocards from the original Acorn Microcomputer onto a
backplane A backplane or backplane system is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used to connect s ...
made the system straightforward to expand in a modular way. The original I/O card, minus its keypad and LED display, became the cassette interface card; while the original
6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...
CPU card, slightly adapted with the addition of a keyboard interface, became the basic CPU card of the system. A series of interchangeable expansion cards were then developed: additional RAM cards; a card containing the Acorn System BASIC interpreter on ROM; a 40×25 character VDU card, and a UHF adaptor for it; interface cards; a
floppy disk controller A floppy-disk controller (FDC) is a hardware component that directs and controls reading from and writing to a computer's floppy disk drive (FDD). It has evolved from a discrete set of components on one or more circuit boards to a special-purpo ...
;
Econet Econet was Acorn Computers's low-cost local area network system, based on a Carrier-sense multiple access with collision detection, CSMA-CD serial protocol carried over a five-wire Bus (computing), data bus, intended for use by schools and sm ...
network cards; an 80×25 character VDU card; and later also alternate processor cards, offering a 6809 or a faster 6502.


System 1

The Acorn System 1, initially called the Acorn Microcomputer (Micro-Computer), was intended for hobbyists. It was based on the
MOS 6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...
CPU, and produced by
British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies. * British national identity, the characteristics of British people and culture ...
company
Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England in 1978 by Hermann Hauser, Christopher Curry (businessman), Chris Curry and Andy Hopper. The company produced a number of computers during the 1980s with asso ...
from 1979. It was a small machine built on two Eurocard-standard
circuit board A printed circuit board (PCB), also called printed wiring board (PWB), is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) ...
s and it could be purchased ready-built or in kit form.


System 2

The Acorn System 2 was offered as a system by
Acorn Computers Acorn Computers Ltd. was a British computer company established in Cambridge, England in 1978 by Hermann Hauser, Christopher Curry (businessman), Chris Curry and Andy Hopper. The company produced a number of computers during the 1980s with asso ...
from 1980. It was the successor to the Acorn Microcomputer (renamed the Acorn System 1). The system comprised four Eurocard-sized
printed circuit boards A printed circuit board (PCB), also called printed wiring board (PWB), is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) ...
mounted in a 19 inch sub-rack frame on an 8-slot
backplane A backplane or backplane system is a group of electrical connectors in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors, forming a computer bus. It is used to connect s ...
, plus a (separately supplied) additional external keyboard. The four PCB cards contained respectively: * a CPU card, containing a 1 MHz
6502 The MOS Technology 6502 (typically pronounced "sixty-five-oh-two" or "six-five-oh-two") William Mensch and the moderator both pronounce the 6502 microprocessor as ''"sixty-five-oh-two"''. is an 8-bit microprocessor that was designed by a small ...
microprocessor, the keyboard interface, and a 2K ROM with the cassette operating system (The 6502 card could be swapped for a 6809.) * a VDU card, providing a 40×25 character
teletext Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipped television sets. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the to ...
-standard display, based on an MC6845 CRT controller and an SAA5050 teletext character generator, * a cassette interface card, * a memory card with 4K of RAM and a 4K
BASIC Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...
ROM. A further 4K of RAM could be added, and also an additional 4K ROM containing floating-point routines and scientific functions. The CPU card and cassette interface card were the same cards as used the
System 1 The Macintosh "System 1" is the first major release of the classic Mac OS operating system. It was developed for the Motorola 68000 microprocessor. System 1 was released on January 24, 1984, along with the Macintosh 128K, the first in the Maci ...
, but with the keypad and LED display of the latter left unused. The system could be expanded with any of Acorn's standard Eurocards to add further functionality. In 1982 it was being offered for £320, or £480 with power supply, plus an additional £136 for the optional keyboard.


System 3

The Acorn System 3 added a floppy disk controller card, floppy disk drive, and disk operating system ROM, replacing the cassette interface card and cassette operating system of the System 2 machine. The System 3 became the standard workhorse for development in the Acorn lab: the Acorn Atom has been called a cut-down version of the System 3; and it was based on the System 3 that much of the development work for the BBC Micro was done. A minimum configuration contained: * A CPU card * A 40×25 Teletext-standard VDU card * 8K RAM with 4K BASIC ROM * A floppy disk controller * One 100K floppy disk drive In 1982 this was being offered for £775, or £1075 with power supply, casing, and two further 8K RAM cards; plus, again, an additional £136 for a keyboard.


System 4

The Acorn System 4 was similar to the System 3, but in a double height frame, containing fourteen slots in the lower frame, and two floppy disk drives in the upper half of the frame above them. With casing, power supply, and a basic 16K of RAM it was being offered for £1525 in 1982 (again, plus extra for the keyboard).


System 5

The Acorn System 5 was the final Acorn rack-mounted system, released in 1983. It was mounted in an extra-height single 19-inch frame, which could accommodate two vertically mounted 5 1/4-inch floppy drives, with either seven or tenAcorn System 5
Chris's Acorns
Eurocard slots. It came complete with a power supply, and was only available fully assembled. As standard it had a 1 MHz 6502, 32K DRAM, a disk controller, and either the 80×25 or the
Teletext Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipped television sets. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the to ...
40×25 VDU cards. Customers could choose which cards to install in the remaining slots, including interface cards, an additional 16K DRAM card, and/or an Econet network adapter; they could also choose to upgrade the processor board to a faster 2 MHz 6502 board.Acorn catalogue, including the System 5
1983 /ref>


References


External links


The Acorn Atom pre-history


{{Acorn_computers System 2 6502-based home computers Computers designed in the United Kingdom Computer-related introductions in 1979