After completing the ZX Spectrum, Steve and Richard decided to start their own company. Both men had enjoyed working with Sinclair's tough deadlines but wanted to be their own bosses. They initially traded as Rainbow, the name Richard Altwasser had originally suggested for Sinclair Research should have called the ZX Spectrum. When finding out that Rainbow was already in use they decided on the name Jupiter Cantab. Cantab is short for Cantabridgian (e.g. of Cambridge). It seemed appropriate as Richard and Steve both held University of Cambridge degrees and also worked with Sinclair there.

At the time nearly every machine came with BASIC as its built in programming language, Richard and Steve felt that the development of a BASIC ROM would take to much time to complete. So the FORTH programming language was chosen, which would also give the machine a unique selling point. FORTH was fast and compact, which would fit the machines specifications, also FORTH was in the press at the time, with a special edition of BYTE magazine in August 1980.

Now what should Jupiter Cantab's first machine be called? In 1950 the National Physical Laboratory made the Pilot ACE (Automatic Computing Engine), one of the earliest British computers. Internally it could store an amount of information measured as 11 Kilobytes, it took 32 microseconds to perform its simplest operation and, with its large number of wires, valves and tubes filled with mercury, occupied a space the size of a small kitchen. Most of its remains can now be seen in the Science Museum at South Kensington. Based on the Pilot ACE, English Electric developed their DEUCE (Digital Electronic Universal Computing Engine). Over six years they sold about forty of these, costing between £30,000 and £40,000 each. Steven and Richard decided to call their machine the Jupiter ACE which was to be sold for £89.95

To support the ACE, Cantab commissioned some software, reported here in Popular Computing Weekly without software the machine would not sell.

Jupiter Cantab went into liquidation in 1983, reported in Popular Computing Weekly and Personal Computer News. The machine, all stock and FORTH rights was then taken over by Boldfield Computing Ltd who commissioned some software for it, including games, database, and spreadsheet. Boldfield also introduced peripherals such as memory packs, and monitor adapters and a full size keyboard. All these and the ACE was sold by mail order, but Boldfield never built any more units, instead selling off the parts for a further two years until they ran out of stock