Acorn achieved much success in the educational market with the BBC Micro, though they struggled to achieve the same feat in other division in which systems like the Acorn Electron participated. Acorn then attempted to break into the business computer scene and they created a new subsidiary: Acorn Business Computers. Acorn Business Computers was founded upon the idea to facilitate their systems with multiple sets of processors and architecture types. They, for example, made plans to include a Z80 processor to support use of CP/M. Tragically for Acorn though, their business division was no success. Acorn only offered 8-bit computers at the time, when 16- and even 32-bit computers already existed and dominated the market. Due to their limited sales, part of Acorn was sold off in 1985 to Olivetti. Late 1985 did, however, bring some new developments for Acorn: the 'Reduced Instruction Set Computer', better known as the RISC processor. This was enough for Oliveti to start funding Acorn again. In June 1987, the first affordable computer with a RISC processor was released: the Archimedes.

The Archimedes had an ARM processor (originally an abbreviation for 'Acorn RISC Machine'), which would become a vital part of many systems and still is today. This computer also had a brand new operating system, RISC OS (originally known as 'Arthur'). BBC BASIC was also present on the system. One interesting thing to note is that the operating system is in ROM. Due to this, the computer starts very fast. Upgrades, however, can only be carried out when the ROM is changed out. The 32-bit system was fully capable of displaying 256 colors and 8-bit sounds.

There were 3 variants released: the A305, the A310 and the A440. Though all these models could be expandable, the A440 was the only one of the three which came with a standard expansion slot and a controller for the internal hard disk. The A305 had 512 KB memory standard, while the A310 had 1 MB. The A440 had 8 times the memory the A305 had with 4 MB. The Archimedes A300 series was succeeded by the Archimedes A3000 in 1989.