Two of Sinclair's earlier lines of products in the late 1970s had been their range of calculators and their Mk 14 development kit. The calculators became more sophisticated with time and also programmable. In 1979, IBM began to sell its Microprocessor CPU board to other manufacturers. Acorn and Sinclair bought it in the UK and Sinclair proceeded to use it to produce what at first appeared to be an upgrade of their calculator. It appears that the company already had plans in place for a computer since they were able to produce the Ambassador within a few weeks.