Econet
Encyclopedia
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".
and Acorn System 2
/3/4 computers in 1981. It became popular as a networking system for the BBC Micro
and Archimedes
computers. The Econet system was eventually supported on all post-Atom Acorn machines except the Electron
, the A3010 and the eventually-cancelled Phoebe 2100. The system was supported by Acorn MOS
, RISC OS
and RISC iX
.
An "Ecolink" interface card for IBM PCs
was available. It used Microsoft
's MS-NET Redirector for MS-DOS
to provide file and printer sharing with the NET USE command.
Acorn Universal Networking (AUN) was an early 1990s implementation of Econet protocols and addressing over TCP/IP, to provide legacy support for Econet on Ethernet-connected machines.
The Econet protocol is also supported by the Linux
kernel, though it is doubtful if anyone has tried using the hardware drivers under Linux 2.6.
Econet is a 5-wire bus network
.
One pair of wires are used for the clock, one pair for data transmission and one wire is a common ground.
Signalling was to the RS-422 5-volt differential standard, with one bit transfer per clock cycle.
Unshielded cable was used for short lengths, and shielded cable for longer networks.
The cable was terminated at each end to prevent reflections and to guarantee high logic levels when the bus was undriven.
The original connectors were five-pin circular 180° DIN types, although on later 32-bit machines (notably the A3020 and A4000) the Econet connection was available via five of the pins on the 15-pin D-type Network port, which could also accept MAUs (Media Attachment Units) to allow other network connections to be used with the same socket. This port looks similar to an AUI port, but is not compatible.
Each Econet interface was controlled by a Motorola MC68B54 Advanced Data Link Controller (ADLC) chip.
Each network segment had a maximum length of 500 meters, and could have up to 254 devices ("stations").
Machines and appliances such as filestores and bridges were configured with unique station numbers using jumpers or CMOS RAM settings.
Network bridges, housed in a standard "BBC Cheese Wedge
" box, were available for building larger networks; up to 127 segments could be bridged together.
The clock signal was generated either by a stand-alone clock box, by a BBC Microcomputer with a modified Issue 4 mainboard or by a Filestore fileserver.
Only one clock generator could be used on each network.
While the network was originally specified to run at 210 kHz, practical clock frequencies could range from about 40 kHz to around 800 kHz; the presence of older machines on the network or the capacitance of a long network cable would reduce the maximum data rate reliably available.
Connections were established using a four-way handshake.
The sender would broadcast.
As Econet was intended as a low-cost local area network, there were only two services that could be expected of a standard Econet network. Acorn provided software for BBC Micro computers to primarily implement a file server, with an optional extra of a printer server. Acorn's tradition of providing full access to the operating system meant that numerous additional services could be added. Computing magazines of the time often carried short utilities such as network chat programs that made use of the Econet protocols without interfering with the basic file and print services.
The original file server was very basic, and essentially implemented network access to a floppy disk. Acorn developed their server software over many years, ending with the Level 4 File Server being the final release. Server software was also provided in the dedicated FileStore units Acorn produced.
Other manufacturers (in particular SJ Research) also produced Econet server hardware which implemented its own versions of the server software. These were compatible with the Acorn implementation, but with additional enhancements.
machines. Previous machines had the capability to accept Econet modules as add ons via an adaptation of the connector used in BBC Master
computers. The Risc PC range used a new network slot connector that would not accept the modules, though a later Econet module was in fact manufactured for this new connector.
The Econet software had mainly moved onto the AUN system by this time, though some suppliers were still offering bridging kits to join old and new together. Econet/AUN was largely superseded by the Acorn Access+ software that operated using native Ethernet
and TCP/IP rather than simulating Econet traffic over a UDP
system. This is turn was superseded by native support for more standard protocols such as Sun NFS and SMB/CIFS.
Econets are now mainly operated by retro-computing enthusiasts. Original hardware is becoming harder and harder to find, with auction sites such as eBay being popular for acquiring Econet hardware such as bridges and FileStores. The 68B54 chip used for communicating with the network is no longer manufactured, though kits for the Model B and Master series are available online.
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
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".
Implementations
Econet was first introduced for use with the Acorn AtomAcorn 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....
and Acorn System 2
Acorn System 2
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....
/3/4 computers in 1981. It became popular as a networking system for 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...
and Archimedes
Acorn Archimedes
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
computers. The Econet system was eventually supported on all post-Atom Acorn machines except the Electron
Acorn Electron
The Acorn Electron is a budget version of the BBC Micro educational/home computer made by Acorn Computers Ltd. It has 32 kilobytes of RAM, and its ROM includes BBC BASIC along with its operating system....
, the A3010 and the eventually-cancelled Phoebe 2100. The system was supported by Acorn MOS
Acorn MOS
Acorn's Machine Operating System or OS was a computer operating system used in the Acorn BBC computer range. It included support for four-channel sound and graphics, file system abstraction, and digital and analogue I/O including a daisy-chained fast expansion bus...
, RISC OS
RISC OS
RISC OS is a computer operating system originally developed by Acorn Computers Ltd in Cambridge, England for their range of desktop computers, based on their own ARM architecture. First released in 1987, under the name Arthur, the subsequent iteration was renamed as in 1988...
and RISC iX
RISC iX
RISC iX was a Unix operating system designed to run on the Acorn Archimedes. Heavily based on 4.3BSD, it was initially completed in 1988 — a year after Arthur but prior to RISC OS.- Features :...
.
An "Ecolink" interface card for IBM PCs
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
was available. It used Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's MS-NET Redirector for MS-DOS
MS-DOS
MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...
to provide file and printer sharing with the NET USE command.
Acorn Universal Networking (AUN) was an early 1990s implementation of Econet protocols and addressing over TCP/IP, to provide legacy support for Econet on Ethernet-connected machines.
The Econet protocol is also supported by the Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
kernel, though it is doubtful if anyone has tried using the hardware drivers under Linux 2.6.
Physical layer
 |
|
| 1 | Data (+ve) |
| 2 | Ground |
| 3 | Clock (+ve) |
| 4 | Data (-ve) |
| 5 | Clock (-ve) |
Econet is a 5-wire bus network
Bus network
A bus network topology is a network architecture in which a set of clients are connected via a shared communications line, called a bus. There are several common instances of the bus architecture, including one in the motherboard of most computers, and those in some versions of Ethernet...
.
One pair of wires are used for the clock, one pair for data transmission and one wire is a common ground.
Signalling was to the RS-422 5-volt differential standard, with one bit transfer per clock cycle.
Unshielded cable was used for short lengths, and shielded cable for longer networks.
The cable was terminated at each end to prevent reflections and to guarantee high logic levels when the bus was undriven.
The original connectors were five-pin circular 180° DIN types, although on later 32-bit machines (notably the A3020 and A4000) the Econet connection was available via five of the pins on the 15-pin D-type Network port, which could also accept MAUs (Media Attachment Units) to allow other network connections to be used with the same socket. This port looks similar to an AUI port, but is not compatible.
Each Econet interface was controlled by a Motorola MC68B54 Advanced Data Link Controller (ADLC) chip.
Each network segment had a maximum length of 500 meters, and could have up to 254 devices ("stations").
Machines and appliances such as filestores and bridges were configured with unique station numbers using jumpers or CMOS RAM settings.
Network bridges, housed in a standard "BBC Cheese Wedge
BBC Cheese Wedge
BBC Micro expansion units, for the BBC Microcomputer were peripherals in a box with the same profile and styling as the main computer.-Second processors:...
" box, were available for building larger networks; up to 127 segments could be bridged together.
The clock signal was generated either by a stand-alone clock box, by a BBC Microcomputer with a modified Issue 4 mainboard or by a Filestore fileserver.
Only one clock generator could be used on each network.
While the network was originally specified to run at 210 kHz, practical clock frequencies could range from about 40 kHz to around 800 kHz; the presence of older machines on the network or the capacitance of a long network cable would reduce the maximum data rate reliably available.
Connections were established using a four-way handshake.
The sender would broadcast.
Services
Being a proprietary network system and protocol, the services available on an Econet while standard in function, were to an extent unique in implementation, particularly in early versions of the file server software.As Econet was intended as a low-cost local area network, there were only two services that could be expected of a standard Econet network. Acorn provided software for BBC Micro computers to primarily implement a file server, with an optional extra of a printer server. Acorn's tradition of providing full access to the operating system meant that numerous additional services could be added. Computing magazines of the time often carried short utilities such as network chat programs that made use of the Econet protocols without interfering with the basic file and print services.
The original file server was very basic, and essentially implemented network access to a floppy disk. Acorn developed their server software over many years, ending with the Level 4 File Server being the final release. Server software was also provided in the dedicated FileStore units Acorn produced.
Other manufacturers (in particular SJ Research) also produced Econet server hardware which implemented its own versions of the server software. These were compatible with the Acorn implementation, but with additional enhancements.
Comparison with modern systems
While Econet can be considered unique amongst network systems and specific to the Acorn range of computers, it does share many commonalities with modern network file systems and protocols:- Remote Procedure CallRemote procedure callIn computer science, a remote procedure call is an inter-process communication that allows a computer program to cause a subroutine or procedure to execute in another address space without the programmer explicitly coding the details for this remote interaction...
- Almost all network operations were performed via a primitive remote procedure call system, either by passing a command line direct to the file server, or by passing an operating system call parameter block. The logon command *I AM was processed by passing the whole command line and reading back the result code.
- Access Permissions - By the time of the Acorn Level 4 File Server and the SJ Research MDFS systems, Econet file servers had a full user name and password system with public and private attributes. These worked similar to Unix permissions without the group field. Files could be set to be readable and/or writable by everyone, just by the user, or both.
- Subnetting - A basic Econet would be a single network segment, which is usually assumed to be network 0. With the use of one or more bridges, it is possible to have up to 127 Econet segments with up to 254 hosts each, for a maximum of 32,258 possible machines.
- Broadcasting - By using host 255, an Econet host could send broadcast packets to all hosts on the network segment. Later implementations of the client software used this to automatically locate file and printer servers.
- Printer Spooling - Later versions of the Econet printer server software used printer spooling to locally cache print jobs before sending to the local printer. This ensured whole print jobs were sent to the printer in one go.
- PortsTCP and UDP portIn computer networking, a port is an application-specific or process-specific software construct serving as a communications endpoint in a computer's host operating system. A port is associated with an IP address of the host, as well as the type of protocol used for communication...
- Because the various protocols (file and printer servers, bridge discovery, and so forth) used clearly defined portshttp://www.heyrick.co.uk/econet/rosource/hdreconet.html, it was quite possible to create additional services, such as BroadcastLoader, AppFS, teletext server, and a range of home grown chat programs and multiplayer games to coexist within the Econet system.
End of Econet
The Econet hardware implementation started to disappear from new Acorn machines around 1993 with the Risc PCRisc PC
The RiscPC was Acorn Computers's next generation RISC OS/Acorn RISC Machine computer, launched on 15 April 1994, which superseded the Acorn Archimedes. The Acorn PC card and software allows PC compatible software to be run....
machines. Previous machines had the capability to accept Econet modules as add ons via an adaptation of the connector used in BBC Master
BBC Master
The BBC Master was a home computer released by Acorn Computers in early 1986. It was designed and built for the British Broadcasting Corporation and was the successor to the BBC Micro Model B. The Master 128 remained in production until 1993....
computers. The Risc PC range used a new network slot connector that would not accept the modules, though a later Econet module was in fact manufactured for this new connector.
The Econet software had mainly moved onto the AUN system by this time, though some suppliers were still offering bridging kits to join old and new together. Econet/AUN was largely superseded by the Acorn Access+ software that operated using native Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
and TCP/IP rather than simulating Econet traffic over a UDP
User Datagram Protocol
The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...
system. This is turn was superseded by native support for more standard protocols such as Sun NFS and SMB/CIFS.
Econets are now mainly operated by retro-computing enthusiasts. Original hardware is becoming harder and harder to find, with auction sites such as eBay being popular for acquiring Econet hardware such as bridges and FileStores. The 68B54 chip used for communicating with the network is no longer manufactured, though kits for the Model B and Master series are available online.