Acorn System 2
Encyclopedia
The Acorn Eurocard systems were a series of modular microcomputer
systems based on rack-mounted Eurocards developed by Acorn Computers 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
, released in March 1980; and also much of the circuitry in its successor, the BBC Micro
, 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 1989.
made the system straightforward to expand in a modular way. The original I/O card, minus its keypad and LCD display, became the cassette interface card; while the original 6502 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 a BASIC interpreter on ROM; a 40×25 character VDU card, and a UHF adaptor for it; interface cards; a floppy disk controller
; Econet
network cards; an 80×25 character VDU card; and later also alternate processor cards, offering a 6809
or a faster 6502.
The Acorn System 2 was offered as a system by Acorn Computers from 1980. It was the successor to the Acorn Microcomputer (renamed the Acorn System 1
).
The system comprised four Eurocard-sized printed circuit boards mounted in a 19 inch subrack frame on an 8-slot backplane
, plus a (separately supplied) additional external keyboard. The four PCB cards contained respectively
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.
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:
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.
Microcomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
systems based on rack-mounted Eurocards developed by Acorn Computers 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
Acorn Atom
The Acorn Atom was a home computer made by Acorn Computers Ltd from 1980 to 1982 when it was replaced by the BBC Micro and later the Acorn Electron....
, released in March 1980; and also much of the circuitry in its successor, the BBC Micro
BBC Micro
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
, 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 1989.
Eurocards
Placing the two Eurocards from the original Acorn Microcomputer onto a backplaneBackplane
A backplane is a group of connectors connected 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 as a backbone to connect several printed circuit boards together to make up a complete...
made the system straightforward to expand in a modular way. The original I/O card, minus its keypad and LCD display, became the cassette interface card; while the original 6502 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 a BASIC interpreter on ROM; a 40×25 character VDU card, and a UHF adaptor for it; interface cards; a floppy disk controller
Floppy disk controller
A floppy disk controller is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive . This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8072A or 82072A and their descendants,...
; Econet
Econet
Econet was Acorn's low-cost local area network system, intended for use by schools and small businesses. Econet is rumoured to be an abbreviation of Economy Network, but Acorn were always careful to stress the Greek root, oikos, meaning "house"....
network cards; an 80×25 character VDU card; and later also alternate processor cards, offering a 6809
Motorola 6809
The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
or a faster 6502.
System 2
Acorn System 1
The Acorn System 1, initially called the Acorn Microcomputer , was an early 8-bit microcomputer for hobbyists, based on the MOS 6502 CPU, and produced by British company Acorn Computers from 1979....
).
The system comprised four Eurocard-sized printed circuit boards mounted in a 19 inch subrack frame on an 8-slot backplane
Backplane
A backplane is a group of connectors connected 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 as a backbone to connect several printed circuit boards together to make up a complete...
, plus a (separately supplied) additional external keyboard. The four PCB cards contained respectively
- a CPU card, containing a 1 MHz 6502 microprocessor, the keyboard interface, and a 2k ROM with the cassette operating system
- a VDU card, providing a 40×25 character teletextTeletextTeletext is a television information retrieval service developed in the United Kingdom in the early 1970s. It offers a range of text-based information, typically including national, international and sporting news, weather and TV schedules...
-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 BASICBASICBASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
ROM. A further 4K of RAM could be added, and also an additional 4K ROM containing floating-point routines and scientific functions.
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.