1/26/20151 ECE 5465 Advanced Microcomputers Acorn RISC History

Outline  History of Acorn Computers prior to RISC (James)  Adoption of RISC & Development of ARM1 (Steve)  Improvements on ARM1 (Pengzhi) 1/26/20152

Pre Acorn RISC (mid 1970’s)  Industry dominated by CISC machines  CISCs were believed to be the most powerful  Many companies with different developments competing for market share. IBM- System/360/370 Motorola DEC- PDP-11 1/26/2015 3

Early History  Acorn Computers Ltd. Established 1978 in Cambridge  Began developing microcomputers  Worked their way into producing systems for engineering and lab users. 1/26/ Herman Hauser and Chris Curry

The Acorn Atom ( )  Conceived by Chris Curry to target the consumer market.  Companies first attempt to enter the consumer market  Progression of MOS Technology 6502 (8 bit microprocessor. Least expensive full-featured microprocessor on the market) Cost 170 pounds 2KB 2MHz RAM (expandable to 12KB) Cassette interface 8KB OS in ROM 1 MHz Video output to tv 1/26/2015 5

Acorn Proton (1981)  In late 1980, Acorn had a prototype computer called the Proton in the design stages of becoming the Atom’s replacement.  Offered far greater expansion capabilities compared to the proton.  Still based on the MOS KB 4MHz RAM 16KB of OS in ROM  Introduced the TUBE Allowed a second processor to be added Proton could be expanded with more sophisticated processors later on. Processing could be farmed out to the second processor leaving the 6502 to perform data input/output. Instrumental in the development of Acorn’s very own processor. 1/26/2015 6

BBC Micro (1981)  In early 1980, the BBC Further Education department wanted a new home computer model with an emphasis on education.  Proton was only at the design stage at the time and the acorn team had one week to build a prototype to show the BBC.  The Proton exceeded BBC’s specifications in every parameter.  Acorn won the contract and the proton was promptly renamed to the BBC micro.  Still based on the 8bit 6502 processor 1/26/2015 7

BBC Micro Success  The release of the Micro caught the crest of the home computer wave in Britain  Success gave Acorn’s design the added credibility of competing machines in the market  Allowed Acorn to advance their design scope. 1/26/2015 8

After the BBC Micro (1983)  The need for a more powerful computer Available microprocessor options were not sufficient for Acorn’s goals. Decided to develop their own  High cost of processor design!!!  Limited company resources and knowledge  But then…..the Berkeley papers were published 1/26/20159

Berkeley Papers  Introduced modern RISC (Reduced Instruction Set Computer) architecture  RISC aims to reduce individual instruction complexity Reduce clock cycles per instruction Easier & Cheaper to design 1/26/201510

Perfect Timing  The release of the Berkeley papers showed that a RISC architecture could be cost effective. Exactly what Acorn Computers was looking for  Inspired Acorn Computers to begin development on their own RISC-based machine 1/26/201511

ARM1  Began development on ARM1 (1983) Fabricated by VLSI Technology Steve Furber and Sophie Wilson  Simulated in BBC BASIC on BBC Micro First commercial RISC processor Less than transistors 3μm process 1/26/201512

ARM1 Continued…  Various key features from the Berkeley design were retained. Load-store architecture Fixed-length 32-bit instructions 3-address instruction formats (2 operand addresses + 1 destination address) 1/26/

Improvements on ARM1  ARM2  From the experience of designing ARM1 the instruction set could be improved in order to maximize the performance of, then the Multiply and Multiply and Accumulate instructions were added.  The addition facilitated real-time digital signal processing, which was to be used to generate sounds, an important feature of home and educational computers  A coprocessor interface was also added to the ARM at this stage, which would enable a floating point accelerator and other coprocessors to be used with the ARM 1/26/201514

Implementation of ARM2  In 1987, a home computer, the Archimedes, was launched as the first commercial using the ARM, featuring an 8MHz version of the ARM2  However, no base of software to provide users with the applications they needed. 1/26/201515

ARM3  ARM3 was launched at the significantly increased clock rate of 25MHz  First integrated memory cache 1/26/201516

ARM LTD  ARM's design was seen to match a definite need for high-performance, low power consumption, low-cost RISC processors.  The Acorn RISC Machine became the Advance RISC Machin Ltd. 1/26/201517

Following ARM Generations 1/26/201518

Current ARM Processors 1/26/201519

Current ARM Processors 1/26/201520

References  ARM System-On-Chip Architecture (Second Edition) Steve Furber  roj01/arm/history.html    2  1/26/201521

Questions? 1/26/201522