Acorn Computers Ltd

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Acorn Computers Ltd. was a British computer company established in Cambridge, England in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro and the Acorn Archimedes.

Acorn's BBC Micro computer dominated the UK educational computer market during the 1980s and early 1990s, drawing many comparisons with Apple in the U.S.

Though the company was closed down in 2000, it leaves an impressive legacy, particularly in the development of RISC personal computers. A number of Acorn's former subsidiaries, notably ARM Holdings, live on today.


Prehistory: Chris Curry and Sinclair Radionics

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The BBC Micro, released by Acorn in 1982.

On 25 July 1961, Clive Sinclair founded Sinclair Radionics to develop and sell electronic devices such as calculators. The failure of the Black Watch wrist watch and the calculator market's move from LEDs to LCDs led to financial problems and Sinclair approached the National Enterprise Board (NEB) for help. After losing control of the company to the NEB, Sinclair encouraged Chris Curry to leave Radionics and get Science of Cambridge (SoC) up and running. In June 1978, SoC launched a microcomputer kit that Curry wanted to develop further but Sinclair could not be persuaded. During the development of the MK14, Hermann Hauser, a friend of Curry's, had been visiting SoC's offices and had grown interested in the product.

CPU Ltd (1978–1983)

Curry and Hauser decided to pursue their joint interest in microcomputers and, on 5 December 1978, they set up Cambridge Processor Unit Ltd (CPU) as the vehicle with which to do this.CPU soon obtained a consultancy contract to develop a microprocessor-based controller for a fruit machine for Ace Coin Equipment (ACE) of Wales. The ACE project was started at office space obtained at 4a Market Hill in Cambridge. Initially, the ACE controller was SC/MP based but soon the switch to a 6502 was made.

The microcomputer systems

CPU had financed the development of a 6502-based microcomputer system using the income from its design-and-build consultancy. This system was launched in January 1979 as the first product of Acorn Computer Ltd, a trading name used by CPU to keep the risks of the two different lines of business separate. Acorn was chosen because the microcomputer system was to be expandable and growth-oriented... and it had the attraction of appearing before "Apple" in a telephone directory. Around this time, CPU and Andy Hopper set up Orbis Ltd to commercialise the Cambridge Ring networking system Hopper had worked on for his PhD but it was soon decided to bring him into CPU as a director because he could promote CPU's interests at the University of Cambridge Computer Laboratory. CPU purchased Orbis and Hopper's Orbis shares were exchanged for shares in CPU Ltd. CPU's role gradually changed as its Acorn brand grew and soon CPU was simply the holding company and Acorn was responsible for development work. At some point Curry had a disagreement with Sinclair and formally left Science of Cambridge but did not join the other Acorn employees at Market Hill until a little while later.

The , upper board; this one shipped on  .
The Acorn System 1, upper board; this one shipped on 9 April 1979.

The Acorn Microcomputer, later renamed the Acorn System 1, was designed by Sophie Wilson. It was a semi-professional system aimed at engineering and laboratory users but its price was low enough, at around £80, to appeal to the more serious enthusiast as well. It was a very small machine built on two cards, one (shown right) with an LED display, keypad, and cassette interface (the circuitry to the left of the keypad), and the other with the rest of the computer (including the CPU). Almost all CPU signals were accessible via a Eurocard connector.

The System 2 made it easier to expand the system by putting the CPU card from the System 1 in a 19" Eurocard rack that allowed a number of optional additions. The System 2 typically shipped with keyboard controller, external keyboard, a text display interface, and a cassette operating system with built-in BASIC interpreter.

The System 3 moved on by adding floppy disk support and the System 4 by including a larger case with a second drive. The System 5 was largely similar to the System 4, but included a newer 2MHz version of the 6502.

The Atom

Development of the ZX80 started at Science of Cambridge in May 1979. Learning of this probably prompted Curry to conceive the Atom project to target the consumer market. Curry and another designer, Nick Toop, worked from Curry's home in the Fens on the development of this machine. It was at this time that Acorn Computers Ltd was incorporated and Curry moved to Acorn full-time.

It was Curry who wanted to target the consumer market – other factions within Acorn (including the engineers) were happy to be out of that market, considering a home computer to be a rather frivolous product for a company operating in the laboratory equipment market. To keep costs down and not give the doubters reason to object to the Atom, Curry asked industrial designer Allen Boothroyd to design a case that could also function as an external keyboard for the microcomputer systems. The internals of the System 3 were placed inside the keyboard, creating a quite typical setup for an inexpensive home computer of the early 80s – the relatively successful Acorn Atom.

To facilitate software development, a proprietary local area network had been installed at Market Hill. It was decided to include this (the Econet) in the Atom and, at its launch at a computer show in March 1980, eight networked Atoms were demonstrated with functions that allowed files to be shared, screens to be remotely viewed and keyboards to be remotely slaved.

The BBC Micro

With the Atom on the market, Acorn could begin to think about its replacement. There were new 16-bit processors coming onto the market – should they move in that direction? After a great deal of discussion, Hauser suggested a compromise – an improved 6502-based machine with far greater expansion capabilities: the Proton. Acorn's technical staff had not wanted to do the Atom and they now saw the Proton as their opportunity to "do it right".1

One of the developments proposed for the Proton was the Tube®: a proprietary interface allowing a second processor to be added. The idea was that processing would be farmed out to the second processor leaving the host to perform I/O. In later years the Tube would play an important role in the development of Acorn's own processor.

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The owl logo of the BBC Series.

In early 1980, the BBC Further Education department conceived the idea of a computer literacy programme, mostly as a follow-up to a BBC documentary, The Mighty Micro, in which Dr. Christopher Evans from the UK National Physical Laboratory predicted the coming (micro)computer revolution. It was a very influential documentary – so much so that questions were asked in parliament. As a result of these questions, the Department of Industry (DoI) became interested in the programme, as did BBC Enterprises, who saw an opportunity to sell a machine to go with the series. BBC Engineering was instructed to draw up an objective specification for a computer to accompany the series.

Eventually, under some pressure from the DoI to choose a British system, the BBC chose the NewBrain from Newbury Laboratories. This selection revealed the extent of the pressure brought to bear on the supposedly independent BBC's computer literacy project – Newbury was owned by the National Enterprise Board, a government agency operating in close collaboration with the DoI. The choice was also somewhat ironic given that the NewBrain started life as a Sinclair Radionics project and it was Sinclair's preference for developing it over Science of Cambridge's MK14 that led to Curry leaving SoC to found CPU with Hauser. The NEB moved the NewBrain to Newbury after Sinclair left Radionics and went to SoC.

Although the NewBrain was under heavy development by Newbury, it soon became clear that they were not going to be able to produce it – certainly not in time for the literacy programme, nor to the BBC's specification. The BBC's programmes, initially scheduled for Autumn 1981, were moved back to Spring 1982. After Curry and Sinclair found out about the BBC's plans, the BBC allowed other manufacturers to submit their proposals. The BBC visited Acorn and were given a demonstration of the Proton. Shortly afterwards, the literacy programme computer contract was awarded to Acorn and the Proton was launched early in 1982 as the BBC Micro.

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Acorn received the Queen's Award for the BBC Micro.

In April 1984 Acorn won the Queen's Award for Technology for the BBC Micro. The award paid special tribute to the BBC Micro's advanced design and it commended Acorn "for the development of a microcomputer system with many innovative features".

The Electron

In April 1982 Sinclair launched the Spectrum. Curry conceived of the Electron as Acorn's sub-200 pound competitor. In many ways a cut-down BBC Micro, it used one Acorn-designed ULA to reproduce most of the functionality. But problems in producing the ULAs led to short supply and the Electron, although launched in August 1983, was not on the market in sufficient numbers to capitalise on the 1983 Christmas sales period. Acorn resolved to avoid this problem in 1984 and negotiated new production contracts.

Acorn Computer Group plc (1983–1985)

The BBC Micro sold spectacularly well - so much so that Acorn's profits rose from a mere £3000 in 1979 to £8.6m in July 1983. In September 1983, CPU shares were liquidated and Acorn was floated on the Unlisted Securities Market as Acorn Computer Group plc, with Acorn Computers Ltd as the microcomputer division. With a minimum tender price of 120p, the group came into existence with a market capitalisation of about £135 million. CPU founders Herman Hauser and Chris Curry leapt instantly into the paper millionaire bracket: Hauser's 53.25 million shares made him worth £64m; Curry's 43 million shares translated into £51m.

A new RISC architecture

Even from the time of the Atom Acorn were considering how to move on from the 6502 - for example, the 16-bit Acorn Communicator developed in 1982 using the 65816.

The IBM PC was launched on August 12 1981. Although a version of that machine was aimed at the enthusiast market much like the BBC Micro, its real area of success was business. The successor to the PC, the XT (EXtended Technology) was introduced in early 1983. The success of these machines, and the variety of Z80-based CP/M machines, in the business sector (and that sector's ability to cope with premium prices) demonstrated that it was a viable market - the development of a business machine looked like a good idea to Acorn. A development programme was started to create a business computer using Acorn's existing technology - the BBC Micro mainboard, the Tube and second processors to give CP/M, MS-DOS and Unix (Xenix) workstations.

This Acorn Business Computer (ABC) plan required a number of second processors to be made to work with the BBC Micro platform. In developing these, Acorn had to implement the Tube protocols on each processor chosen - in the process finding out (during 1983) that there were no obvious candidates to replace the 6502; for example, because of many-cycle uninterruptible instructions, the interrupt response times of the 68000 were too slow to handle the communication protocol that the host 6502-based BBC Micro coped with easily. Development of the National Semiconductor 32016-based model of the ABC range (later sold as the Cambridge Workstation) had shown Sophie Wilson and Steve Furber the value of memory bandwidth. It also showed that an 8MHz 32016 was completely trounced in performance terms by a 4MHz 6502. Furthermore, the Apple Lisa had shown the Acorn engineers that they needed to develop a windowing system - and this was not going to be easy with a 2-4MHz 6502-based system doing the graphics! Acorn would need a new architecture.

Acorn had tested all of the available processors and found them wanting. Having ruled out existing CPUs, it was clear to the developers that that Acorn should seriously consider designing its own processor.

Acornís engineers came across papers on the Berkeley RISC project. They could now handle the truth - if a class of graduate students could create a competitive 32-bit processor, Acorn would have no problem! A trip to the Western Design Center in Phoenix showed Furber and Wilson that they didn't need massive resources and state-of-the-art R&D facilities.

Sophie Wilson set about developing the instruction set, writing a simulation of the processor in BBC Basic that ran on a BBC Micro with a 6502 second processor. It convinced the Acorn engineers that they were on the right track... but before they could go any further they would need more resources. It was time for Wilson to approach Hauser and explain what was afoot. Once the go-ahead had been given, a small team was put together to implement Wilson's model in hardware.

The official Acorn RISC Machine project started in October 1983. VLSI Technology, Inc were chosen as silicon partner since they already supplied Acorn with ROMs and some custom chips. VLSI produced the first ARM silicon on 26 April 1985 – it worked first time and came to be known as ARM1. Its first practical application was as a second processor to the BBC Micro, where it was used to develop the simulation software to finish work on the support chips (VIDC, IOC, MEMC) and to speed up the operation of the CAD software used in developing ARM2. Wilson subsequently coded BBC Basic in ARM assembly language and the in-depth knowledge obtained from designing the instruction set allowed the code to be very dense (a typical Wilson trait), making ARM BBC Basic an extremely good test for any ARM emulator.

Such was the secrecy surrounding the ARM CPU project that when Olivetti were negotiating to take a controlling share of Acorn in 1985 they were not told about the development team until after the negotiations had been finalised.

In 1992 Acorn once more won the Queen's Award for Technology for the ARM.

Financial problems

1984 was Acorn's watershed year – it had gone public just as the home computer market collapsed. It was the year when Atari was sold, Apple nearly went bust, and Acorn had solved the one problem it had had throughout its history: production volumes.

The Electron had been launched in 1983 but problems with the supply of its ULAs meant that Acorn was not able to capitalise on the 1983 Christmas selling period – a successful advertising campaign, including TV advertisements, had led to 300,000 orders but the Malaysian suppliers were only able to supply 30,000 machines. The apparently strong demand for Electrons proved to be illusory: rather than wait, parents bought Commodore 64s or Sinclair Spectrums for their children's presents. Ferranti solved the production problem and in 1984 production reached its anticipated volumes, but the contracts Acorn had negotiated with its suppliers were not flexible enough to allow volumes to be reduced quickly in this (unanticipated) situation – supplies of the Electron built up. Acorn was in real trouble: by the end of the year it had 250,000 unsold Electrons on its hands, which had all been paid for and needed to be stored – at additional expense.

Acorn was also spending a large portion of its reserves on development: the BBC Master was being developed; the ARM project was underway; the Acorn Business Computer entailed a lot of development work but ultimately proved to be something of a flop, with only the 32016-based version ever being sold (as the Cambridge Workstation); and obtaining Federal approval for the BBC Micro in order to expand into the United States proved to a drawn-out and expensive process that proved futile - all of the expansion devices that were intended to be sold with the BBC Micro had to be tested and radiation emissions had to be reduced. Around $20m was sunk into the US operation but the NTSC modified BBC Micros sold barely at all, although they did get an appearance at Supergirl's school!

Acorn Group as an Olivetti subsidiary (1985–1998)

The dire financial situation was brought to a head in February 1985, when one of Acorn's creditors issued a winding up petition. After a short period of negotiations, Curry and Hauser signed an agreement with Olivetti on 20 February. The Italian computer company took a 49.3% stake in Acorn for £12 million, which went some way to covering Acorn's £11 million losses in the previous six months. This valuation fell some £165m below Acorn's peak valuation of £190m. In September 1985, Olivetti took a controlling share of Acorn with 79% of shares.

BBC Master

The BBC Master was launched in February 1986 and met with great success. From 1986 to 1989, about 200,000 systems were sold, mainly to UK schools and universities. A number of enhanced versions were launched - for example, the Master 512, which had 512 KB of RAM and an internal 80186 processor for MS-DOS compatibility, and the Master Turbo, which had a 65C02 second processor.

Archimedes and Risc PC

The first commercial use of the ARM architecture was in the ARM Development System, a Tube-linked second processor for the BBC Master which allowed one to write programs for the new system. It sold for around £4,000, and included the ARM processor and three support chips, 4MB of RAM and a set of development tools with an enhanced version of BBC BASIC.

The second ARM-based product was the Acorn Archimedes desktop-computer, released in mid-1987. The Archimedes was popular in the United Kingdom, Australasia and Ireland, and was considerably more powerful and advanced than most offerings of the day, but the market was already stratifying into the PC dominated world. Acorn continued to produce updated models of the Archimedes including a laptop (the A4) and in 1994 launched the Risc PC where the top specification included a 200MHz+ StrongARM processor. These were sold mainly into education, specialist and enthusiast markets.


Acorn's silicon partner, VLSI, had been tasked with finding new applications for the ARM CPU and support chips. Hauser's Active Book company had been developing a handheld device and for this the ARM CPU developers had created a static version of their processor, the ARM2aS.

Apple was developing an entirely new computing platform, the Newton. Various requirements had been set for the processor in terms of power consumption, cost and performance and there was also a need for fully static operation in which the clock could be stopped at any time. Only the Acorn RISC Machine came close to meeting all these demands, but there were still deficiencies - the ARM did not, for example, have an integral memory management unit (this function being provided by the MEMC support chip) and Acorn did not have the resources to develop one.

Apple and Acorn began to collaborate on developing the ARM, and it was decided that this would be best achieved by a separate company. The bulk of the Advanced Research and Development section of Acorn that had developed the ARM CPU formed the basis of ARM Ltd when that company was spun off in November 1990. Acorn Group and Apple Computer Inc each had a 43% shareholding in ARM, while VLSI were an investor and first ARM licensee.

Set-Top boxes

Acorn Online Media was founded in 1994 to exploit the projected Video-On-Demand (VOD) boom.

In September 1994 the Cambridge Trial of video-on-demand services was set up by Acorn Online Media, Anglia Television, Cambridge Cable and Advanced Telecommunication Modules Ltd (ATML) – the trial involved creating a wide area ATM network linking TV-company to subscribers' homes and delivering services such as home shopping, online education, software downloaded on-demand and the World Wide Web. The wide area network used a combination of fibre and coaxial cable and the switches were housed in the roadside cabinets of Cambridge Cable's existing network. Olivetti Research Laboratory developed the technology used by the trial. An ICL video server provided the service via ATM switches manufactured by ATML, another company set up by Hauser and Hopper. The trial commenced at a speed of 2 Mbit/s to the home, subsequently increased to 25 Mbit/s.

Subscribers used Acorn Online Media set-top boxes. For the first six months the trial involved 10 VOD terminals; the second phase was expanded to cover 100 homes and 8 schools with a further 150 terminals in test labs. A number of other organisations gradually joined in, including NatWest Bank, the BBC, the Post Office, Tesco and the local education authority.

BBC Education tested delivery of radio-on-demand programmes to primary schools and a new educational service, Education Online, was established to deliver material such Open University television programmes and educational software. Netherhall secondary school was provided with an inexpensive video server and operated as a provider of Trial services, with Anglia Polytechnic University taking up a similar role some time later.

It was hoped that Online Media could be floated as a separate company, but the video-on-demand boom never really boomed.

Network Computers

When the BBC's The Money Programme screened an interview with Larry Ellison in October 1995, Acorn Online Media Managing Director Malcolm Bird realised that Ellison's network computer was, basically, an Acorn set-top-box. After initial discussions between Oracle and Olivetti, Hauser and Acorn a few weeks later, Bird was dispatched to San Francisco with Acorn's latest Set Top Box. Oracle had already talked seriously with computer manufacturers including Sun and Apple about the contract for putting together the NC blueprint machine; there were also rumours in the industry that said Oracle itself was working on the reference design. After Bird's visit to Oracle, Ellison visited Acorn and a deal was reached: Acorn would define the NC Reference Standard.

Ellison was expecting to announce the NC in February 1996. Sophie Wilson was put in charge of the NC project and by mid-November a draft NC specification was ready. By January 1996 the formal details of the contract between Acorn and Oracle had been worked out and the PCB was designed and ready to be put into production. In February 1996 Acorn Network Computing was founded. In August 1996 it launched the Acorn Network Computer.

It was hoped that the Network Computer would create a significant new sector in which Acorn Network Computing would be a major player, either selling its own products or earning money from licence fees paid by other manufacturers for the right to produce their own NCs.

Having incorporated its STB and NC business areas as separate companies, Acorn re-organised its PC manufacturing into a further wholly-owned subsidiary, Acorn RISC Technologies (ART). One of ART's major projects was the creation of a new 'consumer device' operating system, Galileo. Galileo's main feauture was a guarantee of a certain quality of service to each process in which the resources (CPU, memory, etc.) required to ensure reliable operation would be kept available regardless of the behaviour of other processes.

The last acorns fall (1998–2000)

Acorn's last real hopes of becoming a major player in the computer industry had fizzled out: set-top boxes were not taking off as expected, and the Network Computer, too, had been a bit of a flop – traditional PCs were reaching the types of prices thought to justify such a design, and increases in bandwidth to the home were slow to come about, making a web connection something of a luxury for the late 90s. Between 1996 and 1998 Olivetti disposed of its interest in Acorn Group through a series of structured transactions, raising £54m. Acorn re-structured its operations, bringing its subsidiary companies back together as divisions within Acorn. Acorn Risc Technologies became the Workstation Division, which was closed in late 1998 when Acorn finally stopped producing desktop-computers in favour of set-top boxes. The last machine (codenamed "Phoebe" or Risc PC 2) was nearly fully developed at the time of the project's abandonment, and therefore was never produced in volume nor sold to the public (notably, numbers of its distinctive yellow case were produced and sold off cheaply).

ARM, however, had gone from strength to strength. In 1998, the Company underwent an initial public offering (IPO) and re-registered as a public company under the name ARM Holdings plc when it completed its IPO and listed its shares for trading on the London Stock Exchange and for quotation on the Nasdaq National Market. Morgan Stanley Dean Witter acted as global co-ordinator and bookrunner for the Offering as well as sponsor and broker for the listing on the London exchange.

In January 1999, Acorn Group changed the name of Acorn Computers Ltd to Element 14 Ltd as it recast itself in the image of ARM – that is as a developer of intellectual property (IP), in this case in the digital signal processing (DSP) market.

By 1999 ARM's share value had increased to a point where the capital value of Acorn Group plc was worth less than the value of its 24% holding in ARM. This situation led shareholders to press Acorn to sell its stake in ARM to provide a return on their investment. The situation also led ARM to consider taking action itself since a financially weak shareholder such as Acorn was putting ARM in a vulnerable position.

Acorn Computers Group plc was purchased on 1 June 1999 by Morgan Stanley Dean Witter Investments Limited. The transaction involved the de-listing of Acorn Group plc, as a result of which its shareholding in ARM was distributed to Acorn's shareholders.

MSDW sold the set-top box division to Pace for £200,000, and Pace thereby acquired control of RISC OS. On 26 July 1999, an Acorn management team led by Stan Boland bought the DSP business, Element 14, from MSDW for £1.5 million Ė its net asset value.

Element 14 subsequently secured £8.25 ($13) million in first round funding from Bessemer Venture Partners, Atlas Ventures and Hauser's Amadeus Capital Partners. It had its headquarters in Cambridge and an engineering facility in Bristol, UK. It headhunted Alcatel's top digital subscriber line (DSL) engineers (including designers of analogue front-end and digital ICs, xDSL modem software and specialists in asymmetric DSL (ADSL) and very high rate DSL (VDSL) systems) and thereby acquired an engineering centre in Mechelen, Belgium.

Element 14 continued to develop its DSP products until it was purchased by Broadcom in November 2000 for £366 ($594) million.


The operating system developed for Phoebe (RISC OS 4, codename Ursula) was made available to Risc PC users by RISCOS Ltd, which licensed the operating system, and continues to develop, support and sell RISC OS today.

However, the market is still competitive with two strands of the OS currently being developed, the 26-bit RISC OS 4 which is currently sold for the Microdigital Omega, and the 32-bit RISC OS 5 for the Castle Iyonix. This competition recently caused a crisis in the community, one that threatened the platform's existence.

See also


  1. "do it right" - quotation from an email from Sophie Wilson.


External links


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