It also enjoyed enthusiastic support in the hobbyist

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Unformatted text preview: standard memory parts. They also had instructions that took many clock cycles to complete (in some cases, many hundreds of clock cycles), giving them very long interrupt latencies. The BBC micro benefited greatly from the 6502's rapid interrupt response, so Acorn's designers were unwilling to accept a retrograde step in this aspect of the processor's performance. As a result of these frustrations with the commercial microprocessor offerings, the design of a proprietary microprocessor was considered. The major stumbling block was that the Acorn team knew that commercial microprocessor projects had absorbed hundreds of man-years of design effort. Acorn could not contemplate an investment on that scale since it was a company of only just over 400 employees in total. It had to produce a better design with a fraction of the design effort, and with no experience in custom chip design beyond a few small gate arrays designed for the BBC micro. Into this apparently impossible scenario, the papers on the Berkeley RISC I fell like a bolt from the blue. Here was a processor which had been designed by a few postgraduate students in under a year, yet was competitive with the leading commercial offerings. It was inherently simple, so there were no complex instructions to ruin the interrupt latency. It also came with supporting arguments that suggested it could point the way to the future, though technical merit, however well supported by academic argument, is no guarantee of commercial success. The ARM, then, was born through a serendipitous combination of factors, and became the core component in Acorn's product line. Later, after a judicious modification of the acronym expansion to Advanced RISC Machine, it lent its name to the company formed to broaden its market beyond Acorn's product range. Despite the change of name, the architecture still remains close to the original Acorn design. Architectural inheritance 37 2.2 Architectural inheritance At the time the first ARM chip was designed, the only examples of RISC ar...
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This document was uploaded on 10/30/2011 for the course CSE 378 380 at SUNY Buffalo.

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