ARM Architecture - History

History

Originally conceived by Acorn Computers for use in its personal computers, the first ARM-based products were the co-processor modules for the BBC Micro series of computers. After achieving success with the BBC Micro computer, Acorn Computers Ltd considered how to move on from the relatively simple MOS Technology 6502 processor to address business markets like the one that would soon be dominated by the IBM PC, launched in 1981. The Acorn Business Computer (ABC) plan required a number of second processors to be made to work with the BBC Micro platform, but processors such as the Motorola 68000 and National Semiconductor 32016 were unsuitable, and the 6502 was not powerful enough for a graphics based user interface.

Acorn would need a new architecture, having tested all of the available processors and found them lacking. After reading white papers on the Berkeley RISC project, Acorn seriously considered designing its own processor. They reasoned if a class of graduate students could create a competitive 32-bit processor, then Acorn would have no problem. A visit to the Western Design Center in Phoenix, where the 6502 was being updated by what was effectively a single-person company, showed Acorn engineers Steve Furber and Sophie Wilson they did not need massive resources and state-of-the-art R&D facilities.

Wilson set about developing the instruction set, writing a simulation of the processor in BBC Basic that ran on a BBC Micro with a second 6502 processor. It convinced the Acorn engineers that they were on the right track. Before they could go any further, however, they would need more resources. Wilson approached Acorn's CEO, Hermann Hauser, and explained his request. Once the go ahead was given, a small team was assembled to implement Wilson's model in hardware.