The BBC Microcomputer System, also called the BBC Micro, is a group of small computers made by Acorn Computers in the early 1980s. These computers were part of the BBC's Computer Literacy Project, which aimed to teach people about computers. The BBC Micro was first released in December 1981 and appeared in several educational BBC TV shows, such as The Computer Programme (1982), Making the Most of the Micro and Computers in Control (both 1983), and Micro Live (1985). Acorn won the contract to create the computer after the BBC asked for proposals. Their early design, called the "Proton" system, was later renamed the BBC Micro.
Although the BBC Micro was announced in late 1981, delays in production caused some orders to be delivered in 1982. It became known as the "Beeb" and was widely used in British schools, helping the BBC achieve its goal of improving computer skills. The BBC Micro was known for its strong build and many connection options, such as ports for extra devices, support for a network called Econet, and the ability to add extra processors. It came in two main versions: the 16 KB Model A (originally priced at £299) and the more popular 32 KB Model B (priced at £399). Even though it was more expensive than many other home computers at the time, it sold over 1.5 million units, partly because of the BBC's reputation and the computer's flexibility.
The BBC Micro had a major influence on education in the United Kingdom. Most schools in Britain purchased at least one unit, introducing many students to basic computer skills. A key feature was its built-in BBC BASIC programming language, which was easy to use and had many useful tools. As a home computer, it also helped create a group of fans who enjoyed its adaptable design, which allowed for features like disk drives and speech synthesis. Its wide range of software and hardware options helped grow the UK's home-made software industry. Acorn's engineers used the BBC Micro to test and design their early ARM computer chips, which are now used in many devices worldwide. This work helped speed up the development of efficient computer technology used in mobile phones, devices with limited space, and other systems.
The BBC Micro had different display settings, including a simple Mode 7 based on Teletext technology. It had a full-sized keyboard with ten keys that users could customize. It included standard inputs, a serial and parallel port, and a cassette interface that used the CUTS version of the Kansas City standard. In total, nine BBC-branded computers were made, but the term "BBC Micro" usually refers to the first six models: Model A, B, B+64, B+128, Master 128, and Master Compact. Later models were part of Acorn's Archimedes series.
History
During the early 1980s, the BBC launched a program called the BBC Computer Literacy Project. This program was partly started because of an ITV documentary series called The Mighty Micro, in which Christopher Evans from the UK's National Physical Laboratory talked about how microcomputers would change the economy, industry, and daily life in the United Kingdom.
The BBC Computer Literacy Project was planned by the BBC's Continuing Education Television department. With help from the Manpower Services Commission, the department studied microcomputers and created a report called Microelectronics in 1979. This report was sent to all UK Members of Parliament. The report said people should learn to use and control computers, not feel controlled by them.
The BBC wanted to use a microcomputer that could perform many tasks for a TV series called The Computer Programme. Topics covered included programming, graphics, sound and music, teletext, controlling outside devices, and artificial intelligence. The BBC created detailed requirements for a computer and discussed the project with companies like Acorn Computers, Sinclair Research, Newbury Laboratories, Tangerine Computer Systems, and Dragon Data.
Some people disagreed with the BBC's decision to focus on a specific microcomputer for the project. Critics said the BBC was promoting a commercial product instead of supporting existing education and training networks. Others claimed the BBC was acting like a government tool, using the Computer Literacy Project to support industry indirectly without clear public funding.
At the same time, the Acorn team was working on a new computer called the Proton, which would replace their older Atom model. The Proton had better graphics and a faster 2 MHz MOS Technology 6502 central processing unit. The design was still being planned, and the team, including Steve Furber and Sophie Wilson, had only one week to build a working model from sketches. They worked late into the night to complete the prototype for the BBC. Although the BBC expected a computer with the Zilog Z80 CPU and CP/M operating system, the Proton met all the BBC's requirements and even exceeded them in most areas.
Based on the Proton prototype, the BBC signed a contract with Acorn in February 1981. By June, the BBC Micro's specifications and prices were finalized. To meet the BBC's request for compatibility with CP/M, a Tube interface was added to the design, allowing a Z80 second processor to be used. In 1984, Acorn and BBC Enterprises agreed to a new four-year contract, with other companies also bidding for the deal. An Acorn representative noted that the BBC Model B would not remain competitive during the contract period and that a newer version would eventually be developed.
The OS ROM v1.0 includes an ASCII credits string (code here). Also, the last bytes of the BASIC read-only memory (ROM; versions 2 and 4) contain the word "Roger," which refers to Sophie Wilson, whose name at the time was Roger Wilson.
Market impact
The BBC Microcomputer was released on December 1, 1981. However, production problems caused most of the first batch to be delivered in 1982. It was nicknamed "the Beeb" and became popular in the UK, especially in schools. By 1985, about 80% of British schools had a BBC Microcomputer.
Byte magazine called the BBC Micro Model B "a no-compromise computer with many uses beyond learning about computers." It praised the Tube interface as the most innovative feature and said no other British computer offered the same level of versatility or expansion capability. Like the Sinclair ZX Spectrum and Commodore 64, which were released in 1982, the BBC Micro faced high demand, leading to long delays in delivering orders.
Acorn tried to market the BBC Micro in the United States and West Germany. In the US, they focused on the education market, which was worth about $700 million. They sold an upgraded version of the Model B with added features, such as speech synthesis and a built-in network interface, for $995. They also provided software and teaching materials to help schools adopt the computer.
By October 1983, American schools had ordered $21 million worth of BBC Micros. In Lowell, Massachusetts, 138 BBC Micros were installed in eight schools, with the computer’s networking features, educational value, and available software being key reasons for its selection over competitors like IBM, Apple, and Commodore. In Phoenix, Arizona, 175 BBC Micros were installed, with a local dealer predicting $2 million in sales within two years, mostly for education. By early 1984, Acorn claimed over 1,000 US dealers and reported "over $50 million worth of education orders" for the BBC Micro system.
In October 1984, Acorn claimed to have sold 85% of the computers in British schools and was delivering 40,000 units per month. That December, Acorn aimed to become the top seller of educational computers in the US. The New York Times highlighted the importance of local area networking for teachers. Although some ads were placed, the US expansion eventually failed.
The BBC Micro’s success in the UK was due to its use in teaching computer skills and information technology. Acorn became well-known for the BBC Model B. Some Commonwealth countries, like India, started their own computer literacy programs around 1984 and used the BBC Micro to avoid repeating work already done in the UK. Clones of the BBC Micro, such as the SCL Unicorn and Dolphin, were made in India and other countries.
Acorn partnered with companies in India and Mexico to produce the BBC Micro from kits. In India, several thousand units were made monthly, while in Mexico, plans called for 2,000 units monthly by 1985. These machines were intended for markets in the Americas. After Acorn left the US in 1986, Mexican manufacturer Datum continued producing 7,000 to 8,000 Spanish-language units yearly.
The BBC’s computer literacy project aimed to sell the BBC Micro for less than £200. Initially, the Model A and Model B cost £235 and £335, but prices rose quickly. By 2011, the Model B’s price of nearly £400 would be about £1,200 in today’s money. Acorn expected to sell 12,000 units but eventually sold over 1.5 million. To compete with cheaper models like the ZX Spectrum and Commodore 64, Acorn later released a simplified version called the 32K Acorn Electron.
The BBC’s involvement in microcomputing led ITV network companies to consider creating their own computer system. A CP/M-based system by Transam Computers was proposed but rejected due to concerns about conflicts of interest and broadcasting rules. A related product, the Wren, was later developed but not widely adopted. Not all ITV companies supported plans to promote microcomputing or sell computers.
Description
The BBC Micro computer was designed with a special type of memory called random-access memory (RAM), which helped it work quickly. Many computers from that time used a method where the RAM ran twice as fast as the central processing unit (CPU). This allowed the computer's video system to use the memory while the CPU was working on other tasks. This sharing of memory was used in other computers like the Apple II Plus and early Commodore models.
However, the BBC Micro was different. It had a faster CPU, running at 2 million cycles per second, which was twice as fast as some earlier computers. This speed made it harder for the CPU and video system to share memory without causing problems, known as bus contention. Some computers, like the Amstrad CPC and Atari 8-bit systems, dealt with this issue by accepting slower performance. Others, like the MSX systems, used separate memory sections for the CPU and video.
Acorn, the company that made the BBC Micro, wanted the CPU and video system to share memory without interference. To do this, the RAM needed to handle 4 million memory accesses each second. A special type of memory called DRAM, the HM4816 from Hitachi, was the only one fast enough. Hitachi sent the few available chips directly to Acorn.
A component called the National Semiconductor 81LS95 multiplexer was needed for the high-speed memory. When other companies tried to replace it, their parts didn’t work, but the original one continued to function correctly even after millions of computers were made. Another issue was the 6502 CPU’s data bus, which caused the prototype to fail. Engineers found that placing a finger on a specific spot on the motherboard fixed the problem. They added a resistor pack to the data bus, a solution that remained unexplained but worked.
The BBC Micro Model A had 16 kilobytes of user memory, while the Model B had 32 kilobytes. Extra memory could be added using special chips. The computer had three video ports: one for TV signals, one for computer monitors, and one for high-quality RGB signals used in TV programs. This RGB port allowed the BBC Micro to be used in television shows like The Computer Programme.
The BBC Micro included several input and output ports, such as serial and parallel printer ports, a digital input/output port, and a port for analog signals. It also had a special connector called the "1 MHz bus" for adding extra hardware. Options like a network interface (Econet) and a disk drive were available, though Econet was rarely used.
A unique feature was the "Tube" interface, which allowed a second processor to be added. These processors were based on the 6502, Z80, and 32016 CPUs. The Tube was used for upgrades like running CP/M software on the BBC Micro. Special memory pages, each with a name, controlled access to the computer’s input/output systems.
The Model A and Model B used the same printed circuit board. Upgrading a Model A to a Model B involved adding more memory and a specific chip. Some upgrades required soldering. Early versions of the BBC Micro ran on a software called "OS 0.1," with later updates released as integrated circuits.
The BBC Model A was replaced by the Acorn Electron. Early BBC Micros used power supplies that avoided electromagnetic interference, but these were later replaced with more reliable switched-mode units. Some Model Bs had a buzzing noise from the speaker, which could be fixed by adding a resistor.
There were five versions of the BBC Micro’s circuit board, labeled from "Issue 1" to "Issue 7." Export models included versions for the US and West Germany. The name "BBC Micro" was fully spelled out to avoid confusion with another company. US models had changes to fit American TV standards, but these were later sold in the UK. In 1985, Acorn released the Model B+ with 64 kilobytes of RAM, though it had limited success.
Successor machines
In 1985, Acorn created its own 32-bit Reduced Instruction Set Computing (RISC) CPU called the ARM1. Furber made a model of the processor on the BBC Micro using 808 lines of BASIC, and Arm Ltd. still keeps copies of this code for legal reasons. The first ARM prototype systems, the ARM Evaluation System and the A500 workstation, worked as extra processors connected to the BBC Micro's Tube interface. Acorn employees built the A500's operating system while it was linked to the BBC Micro through the Tube. Over time, the A500's built-in input and output ports were activated, allowing it to operate independently as a complete computer. In 1987, an improved version of the processor was used to introduce the first four models in the Archimedes series. Three of these models were eventually released, with the two models having less memory (512 KB and 1 MB) featuring the BBC Microcomputer logo and red function keys. Although the Archimedes was not very successful, the ARM processor family later became the most common type of processor used in mobile devices, especially mobile phones.
Acorn's final BBC-related model, the BBC A3000, was released in 1989. It was essentially a 1 MB Archimedes computer designed to fit into a single unit.
Retro computing scene
In 2015, Furber said he was surprised that the BBC Micro became known for being reliable, even though much of its design was based on guesswork. As of 2018, the BBC Micro is still used today because of its ability to expand easily and connect with other devices. A group of people who enjoy using old computers, called a retrocomputing community, continue to find new ways to use the BBC Micro. Some BBC Micros are still in museums across the United Kingdom, and in 2004, the Jodrell Bank observatory used one to control its 42 ft radio telescope. Furber noted that the BBC Micro had very small safety margins in its design, but at a retrocomputing meeting, users reported that after 30 years, only the capacitors in the power supply needed replacing, and all other parts still worked. The Archimedes computer included 65Arthur, a program that allows many BBC Micro programs to run. Other programs, like Beebdroid for Android and JS Beeb for the web, also let users run BBC Micro software on different systems.
In March 2008, the people who created the BBC Micro met at the Science Museum in London. An exhibition about the computer and its history was planned for 2009. The UK National Museum of Computing at Bletchley Park uses BBC Micros to teach school children about programming. In March 2012, the BBC and Acorn teams that worked on the BBC Micro and the Computer Literacy Project gathered for a 30th anniversary event called "Beeb@30." This event took place at Arm’s offices in Cambridge and was hosted by the Centre for Computing History.
Even after the BBC Micro was replaced by newer technology, additional hardware and software were created for it. Examples include Sprow’s 1999 zip compression tool and a ROM update to fix a Y2K issue in the BBC Master. Many websites today still support the development of hardware and software for BBC Micros and Acorn computers.
Specifications
The BBC Micro, like the IBM PC with its Color Graphics Adapter, had video settings that could be changed using software. These settings included options for 20- to 40-column text, which worked well with a home television, and 80-column text, which required a high-quality RGB-connected monitor. The 80-column mode was often too blurry when viewed on a home TV through the UHF output. These different settings allowed users to balance color depth, screen clarity, and memory use. In the earliest models, the operating system and programs used the leftover memory after the display settings were set.
Mode 7 was a special Teletext mode, which used very little memory. It was created because the BBC used broadcast teletext (Ceefax) and made the computer useful as a Prestel terminal. This mode used a chip called the SAA5050 to display teletext characters on monitors and TVs without a Teletext receiver. Mode 7 stored text as ASCII codes in only 1 KB of video memory, unlike other modes that stored images as bitmaps.
Modes 0 to 6 could display colors from a set of 16 options: eight basic colors from the RGB color cube and eight flashing colors made by alternating basic colors with their opposites. These colors could be changed without altering the display memory. Modes 3 and 6 were text-only settings that used less memory by reducing the number of text rows and adding blank lines between them. Mode 6 used the least memory, requiring only 8 KB for video storage. These modes could also display special characters like diacritics. All modes except Mode 7 supported bitmapped graphics, but commands for drawing or plotting had no effect in text-only settings.
The BBC B+ and later Master models included "shadow modes," which stored the 1–20 KB frame buffer in a separate RAM bank. This freed up main memory for user programs. Shadow modes were activated by setting bit 7 of the mode variable, which allowed users to select modes 128–135.
A speech upgrade based on the Texas Instruments TMS5220 chip played sampled words spoken by BBC newscaster Kenneth Kendall. This feature was standard on the US model, which used an American vocabulary. The Computer Concepts Speech ROM also used the TMS5220 chip but did not include speech ROMs, instead controlling the chip directly. The speech upgrade was not widely sold and was later replaced by software-based synthesizers from Superior Software that used standard sound hardware.
The speech upgrade added two empty sockets next to the keyboard, intended for 16 KB serial ROM cartridges containing extra speech data or general software. However, few games or software were developed for these sockets due to low sales of the speech upgrade and other economic concerns. The space next to the keyboard, nicknamed the "ashtray," was more commonly used for other upgrades, such as a ZIF socket for standard paged ROMs.
Use in the entertainment industry
The BBC Domesday Project was an important project that used new technology. It was based on a changed version of the BBC Micro's next model, the BBC Master.
Musician Vince Clarke, who was part of the British synth pop bands Depeche Mode, Yazoo, and Erasure, used a BBC Micro and later a BBC Master with the UMI music sequencer to create many songs. In music videos from the 1980s that feature Vince Clarke, a BBC Micro is often shown or used to create text and graphics, such as in a clip for Erasure's song "Oh l'amour." The band Queen used the UMI Music Sequencer on their album A Kind of Magic. The UMI is also listed in the CD booklet. Other bands that used the BBC Micro for music creation include A-ha and the reggae band Steel Pulse. Paul Ridout was listed as "UMI programmer" on the 1986 solo album The Lace by Benjamin Orr, the bassist and vocalist of the band Cars. Other people who used the UMI included Blancmange, Alan Parsons, and Mutt Lange. The band Black Uhuru used the Envelope Generator from SYSTEM software (Sheffield) running on a BBC Micro to create some of the electro-dub sounds on their 1983 album Try It.
The BBC Micro was widely used to create graphics and sound effects for many early 1980s BBC TV shows. These included series 3 and 4 of The Adventure Game; the children's quiz show "First Class" (where the onscreen scoreboard was made by a BBC Micro nicknamed "Eugene"); and many 1980s episodes of Doctor Who, such as "Castrovalva," "The Five Doctors," and "The Twin Dilemma."
Legacy
In 2013, NESTA published a report about the history and effects of the BBC Micro, including its role in the BBC Computer Literacy project. In June 2018, the BBC shared its archives from the Computer Literacy Project.
The BBC Micro had a long-term influence on education by creating a common way of teaching about the hardware and software used in the system, especially the programming language BBC BASIC. It also encouraged schools to invest heavily in software for the machine. Because of this, companies that made competing systems, such as IBM PC compatibles, Apple Macintosh, Commodore Amiga, and Acorn (which later made the Archimedes, a successor to the BBC Micro), had to make their systems work with the many BBC Micro computers already in use in schools.