The System 1 (originally known simply as the Acorn Microcomputer) was a very small machine built on two cards, one with an LED display and hexpad , and the other with the rest of the computer (including the CPU). Although the machine was based on the eurocard standard, it did not include connectors to allow it to be attached to other eurocard devices. This made it useful for hobby purposes only.
This was addressed in the System 2, which put the CPU card from the System 1 in a 19" eurocard rack which included a number of optional additions. The System 2 typically shipped with keyboard controller, and external keyboard, and a text display interface. The System 3 added floppy support and built-in BASIC, the and System 4 added 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.
In 1980 they took the internals of the System 3 and placed them inside the case of the external keyboard, creating the much more successful Acorn Atom. Work started almost immediately on a newer version of the Atom known as the Proton with better graphics, expansion abilities, and the 2MHz 6502 as in the System 5.
The success of Atom prompted the British Broadcasting Corporation to include Acorn to the list of computer manufacturers with whom they discussed a contract for a microcomputer suitable to back their TV series The Computer Programme. The BBC awarded Acorn the contract after seeing the prototype Proton, and the machine was renamed as the BBC Microcomputer in November 1981. During the next five years, a number of improved versions of the same design was launched, including the Acorn Electron, BBC Model B+ and BBC Master in several variants.
In 1983 Acorn asked Intel for a sample 80286 processor, and Intel refused. As a result of this refusal, and dissatisfaction with other cpu options such as the Motorola 68000, a team was set up within Acorn, led by Roger Wilson and Steve Furbur, to try and develop a RISC (Reduced Instruction Set Chip) processor. Such was the secrecy surrounding this project that when Olivetti[?] took a controlling share of Acorn in 1985 they were not told about the development team until after the negotiations had been finalised. This effort led to the ARM (Acorn RISC Machine) chip.
The first ARM-based product was the ARM Development System, a second processor for the BBC Master which allowed one to write programs for the new system. It cost around £4,000 to buy, and included the ARM processor and three support chips, 4 Mb 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 the Risc PC where the top specification included a 200MHz+ StrongARM processor. These were sold mainly into education, specialist and enthusiast markets until Acorn finally abandoned producing desktop-computers in late 1998 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). The operating system developed for Phoebe (codename Ursula or RISC OS 4) was made available to Risc PC users by RISC OS Ltd.[?], which licenced the operating system, and continues to develop, support and sell RISC OS today.