The Acorn Archimedes is a family of personal computers designed by Acorn Computers of Cambridge, England. The systems in this family use Acorn's own ARM architecture processors and initially ran the Arthur operating system, with later models introducing RISC OS and, in a separate workstation range, RISC iX. The first Archimedes models were introduced in 1987, and systems in the Archimedes family were sold until the mid-1990s alongside Acorn's newer Risc PC and A7000 models.
The first Archimedes models, featuring a 32-bit ARM2 RISC CPU running at 8 MHz, provided a significant upgrade from Acorn's previous machines and 8-bit home computers in general. Acorn's publicity claimed a performance rating of 4 MIPS.These being equivalent to VAX-11/750 instructions. Later models featured the ARM3 CPU, delivering a substantial performance improvement, and the first ARM system-on-a-chip, the ARM250.
The Archimedes preserves a degree of compatibility with Acorn's earlier machines, offering BBC BASIC, support for running 8-bit applications, and display modes compatible with those earlier machines. Following on from Acorn's involvement with the BBC Micro, two of the first models—the A305 and A310—were given BBC branding.
The name "Acorn Archimedes" is commonly used to describe any of Acorn's contemporary designs based on the same architecture. This architecture can be broadly characterised as involving the ARM CPU and the first generation chipset consisting of MEMC (MEMory Controller), VIDC (VIDeo and sound Controller) and IOC (Input Output Controller).
History Having introduced the BBC Micro in 1981, Acorn established itself as a major supplier to primary and secondary education in the United Kingdom. However, attempts to replicate this dominance in other sectors, such as home computing with the BBC Micro and Acorn Electron, and in other markets, including the United States and West Germany, were less successful.
As microprocessor and computing technology advanced in the early 1980s, microcomputer manufacturers had to consider evolving their product lines to offer increased capabilities and performance. Acorn's strategy for business computing and development of more capable machines involved a range of "second processor" expansions, including a Z80 second processor running the CP/M operating system, a commitment made by Acorn when securing the BBC Micro contract.
Meanwhile, established platforms like CP/M running on Z80 processors faced competition from the IBM PC running PC DOS and computers with a variety of operating systems on Intel processors such as the 8088 and 8086. Systems using the Motorola 68000 and other processors running the Unix operating system also became available. Apple launched the Lisa and Macintosh computers, and Digital Research introduced its own GEM graphical user interface software, building on previous work by Xerox.
Acorn's strategy seemingly evolved to align with Torch Computers—a company that Acorn considered acquiring—which had already combined BBC Micro hardware with second processors (and modems) to produce their Communicator product line and derivatives. In 1984, Acorn introduced the Acorn Business Computer (ABC) range, based on the BBC Micro architecture, offering models with different second processors and capabilities to respond to computing trends at the time. These models received generally favourable reviews from the computing press. However, with Acorn facing financial strain, the company was rescued by Olivetti in 1985, leaving the ABC's future uncertain in the expected restructuring process. Ultimately, only one of the variants—the Acorn Cambridge Workstation—would reach the market, in a somewhat different form than originally planned.
The demise of the Acorn Business Computer left Acorn purely with a range of 8-bit microcomputer products, leaving the company vulnerable to competitors introducing 16-bit and 32-bit machines. The increasing dominance of MS-DOS in the business market and advocacy for the use of such software in the education sector left Acorn at risk of potential exclusion from its core market. Meanwhile, competing machines attempted to offer a degree of compatibility with the BBC Micro, enticing schools to upgrade to newer, more powerful non-Acorn machines while retaining access to software developed and purchased for Acorn's "aging machine". Acorn's ability to respond convincingly to these competitive threats was evidently constrained: the BBC Model B+ was merely a redesigned BBC Model B (with some heritage in the ABC endeavour) providing some extra memory but costing more than its predecessor, being labelled as a "stop gap" by Acorn User's technical editor, expressing frustration at opportunities not taken for cost reduction and at a general lack of technological innovation in that "Acorn has never shown interest in anything as exciting as the 68000". Disillusionment was sufficient for some software producers to signal a withdrawal from the Acorn market.
Other commentators who responded to the B+ suggested that Acorn pursue the second processor strategy more aggressively, leveraging the existing user base of the BBC Micro while those users were still using the machine. In 1986, Acorn introduced the BBC Master series, starting with the Master 128 which re-emphasised second processors in the form of internally fitted "co-processors". Although a modest evolution of the existing 6502-based platform, enthusiasm for the series was somewhat greater than that for the B+ models, with dealers and software developers citing the expansion capabilities and improved compatibility over the B+. However, the competitiveness of these co-processors proved to be constrained by hardware limitations, compatibility and pricing, with a Master 512 system featuring a Master 128 and 80186 co-processor comparing unfavourably to complete IBM PC-compatible systems. The planned Master Scientific product was never launched, leaving potential customers with the existing Cambridge Co-Processor expansion as their only available option.
Attitudes towards Acorn and its technological position changed somewhat in late 1985 as news of its RISC microprocessor development effort emerged, potentially encouraging Olivetti to continue its support for the company at "a critical stage" in its refinancing of Acorn. Subsequent commentary suggested the availability of this microprocessor—the Acorn RISC Machine—in future computers as well as in an evaluation board for the BBC Micro, although such a board—the ARM Evaluation System—would only be announced in mid-1986 at a cost of £4500. Having also developed the additional support chips required to make up a complete microcomputer, Acorn was regarded as having leapt ahead of its nearest competitors.
On the eve of the announcement of Acorn's 32-bit ARM-based microcomputer products, prototypes designated A1 and A500 were demonstrated on the BBC television programme Micro Live exhibiting BASIC language performance ten times faster than a newly introduced 80386-based computer from perennial education sector rival Research Machines, with suggestions made that the machines would carry the BBC branding. Revealingly, Acorn's managing director noted, "Over the past two years we've paid the price of having no 16-bit micro."Acorn had, in fact, produced the 16-bit Acorn Communicator for specialised markets, the Master 512 variant of the BBC Master series, and had sold the Olivetti M19 under its own brand. The company had also sold the 32-bit Acorn Cambridge Workstation to academic and scientific markets.
Models
The first available models in the family were the A305, A310 and A440, introduced in 1987, followed by the A3000, A410/1, A420/1 and A440/1 in 1989, A540 in 1990, A5000 in 1991, A4 in 1992, with the A3010, A3020 and A4000 being the final models, also introduced in 1992.
A300 and A400 series
Powered by an ARM2 (Acorn RISC Machine) processor, the Acorn Archimedes was variously described as "the first RISC machine inexpensive enough for home use", and "the first commercially-available RISC-based microcomputer".Note that the IBM RT PC, and certain HP PA-RISC workstations were already available in 1986. The SGI IRIS 4D series was also introduced in March 1987. The first models were released in June 1987, as the 300 and 400 series. The 400 series included four expansion slots and an ST-506 controller for an internal hard drive, whereas the 300 series required the addition of a backplane to gain expansion slot capabilities. A two slot backplane could be added to the 300 series as an official upgrade, with the possibility of 4-slot backplane being available from third parties, but a hard drive expansion card was also required for these machines, occupying one slot.
Both series included the Arthur operating system (later replaced by RISC OS as a paid-for upgrade), BBC BASIC programming language, and an emulator for Acorn's earlier BBC Micro, and were mounted in two-part cases with a small central unit, monitor on top, and a separate keyboard and three-button mouse (the middle one used for pop-up context menus of the operating system). All models featured eight-channel 8-bit stereo sound and were capable of displaying 256 colours on screen.
Three models were initially released with different amounts of memory, the A305, A310 and A440. The 400 series models were replaced in 1989 by the A410/1, the A420/1 and A440/1, these featuring an upgraded MEMC1a and RISC OS. Earlier models which shipped with Arthur could be upgraded to by replacing the ROM chip containing the operating system. Because the ROM chips contained the operating system, the computer booted instantly into its GUI system, familiar from the Atari ST.
Despite the A310 being limited to 1 MB of RAM officially, several companies made upgrades to 2 MB and 4 MB, with the smaller upgrades augmenting the built-in RAM and the larger upgrades replacing it entirely. The 400 series were officially limited to 4 MB of RAM, but several companies released 8 MB upgrades that provided an extra MEMC chip plus 4 MB of RAM to complement an existing 4 MB of fitted RAM.
A3000
In early 1989, speculation about new machines in the Archimedes range envisaged a low-cost, cut-down model with 512 KB of RAM to replace the A305 in a fashion reminiscent of the Master Compact. This speculation evolved to more accurately predict a machine with 1 MB of RAM aimed at junior or primary schools. Other commentators correctly predicted the provision of an internal disc drive and a single "special" podule slot. However, any new, low-cost product providing support for up to 2 MB of RAM also raised questions about the future of the 300 series, given the limitation of the 300 series to a maximum of 1 MB at that time.
Concurrently with these rumoured product development efforts, work had commenced on a successor to the Arthur operating system, initially named Arthur 2 but renamed to RISC OS 2 for launch. In May 1989, a number of new machines were introduced along with RISC OS 2: the 300 series was phased out in favour of the new BBC A3000, and the 400 series were replaced by the improved 400/1 series models. Having been developed in a "remarkably short timescale of nine months", the machine was the "major learning vehicle" for an integrated CAD system introduced at Acorn employing products from Valid Logic Systems, and it was reported that the A3000 was the first home microcomputer to use surface mount technology in its construction, with the machine being built at Acorn's longstanding manufacturing partner, AB Electronics.