The first ARM chip, the Acorn RISC Machine (which was later changed and referred to Advanced RISC Machine), was developed by a advanced research and development team at Acorn Computers, a pioneering developer of microcomputers in the UK. At the time Acorn was one of the leading names in the British personal computer market.


Acorn's initial success was sealed when the British Broadcasting Corporation (BBC) commissioned a new home computer model from the company to be sold as the BBC Microcomputer.  The release of the BBC Micro in 1982 caught the crest of the home computer wave in Britain, and the BBC name gave Acorn's design the added credibility compared with competing machines from many other developers in this market.  The BBC Micro was based around the 8 bit 6502 processor from Rockwell, the same chip that powered the Apple II.  Initial models featured colour graphic and 32 kbytes of random access memory.  Data was stored on audiocassettes; hard and floppy disk drive interfaces were also available.





Work on the development of what was to become the ARM began in 1983.  Working samples were received in 1985.  Steve Furber, now ICL Professor of Computer Engineering at Manchester University, Roger Wilson, who had worked on the design of the BBC Micro, and Robert Heaton who led the VLSI design group within Acorn made up the team developing it.  The team worked to create a chip which met their requirements of a processor which retained the ethos of the 6502 but in a 32-bit RISC environment, and implemented this in a small device which it would be possible to design and test easily, and to fabricate cheaply. The important initial decisions were to use a fixed instruction length and a load/store model.  Other design decisions were made on an instruction by instruction basis. 


The first model of the ARM (ARM1) instruction set was written in BASIC. The subsequent model of the ARM hardware was written in BASIC as well.  The actual physical design of the chip was achieved using VLSI Technology's custom design tools.  In addition, an event-driven simulator was designed, also in BASIC, which allowed the support chips, the video controller VIDC and memory controller MEMC, and the I/O controller IOC, to be designed and tested. A development of the simulator, since rewritten in Modula-2 and then in C and known as ASIM, is still used by both Acorn and ARM LTD for design and testing today.


The world's first commercial RISC processor and first ARM processor, ARM1, yield working silicon the first time it was fabricated, in April 1985 at VLSI Technology.  It bettered the stated design goals while using fewer than 25,000 transistors. These samples were fabricated using 3μm process.






The experience of designing ARM1, and of programming the sample chips, showed that there were some areas where the instruction set could be improved in order to maximize the performance of systems based around it.  In particular, 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.  The later developed ARM2 still maintained its small die size and low transistor count with all these additions.





In 1985 a financial crisis enveloped Acorn and led to it being taken over by the Italian giant Olivetti Ing et Cie, one of Europe's leading computer and office equipment manufactures.  The company took over without knowing that Acorn's research labs housed the first sample of a new family of RISC processors.  Although the ARM processor had been with the clear intention that it was to power the next generation of Acorn personal computers, and it was equally clear that such a machine needed to be developed quickly, the design and production of ARM-based system by Acorn was to be more fraught than the design of the chip themselves.  It was to take more than two years from the arrival of working ARM silicon to the launch and shipment of a complete ARM-based system.


In 1987, a home computer, the Archimedes, was launched as the first commercial using the ARM, featuring an 8MHz version of the ARM2 and the three support chips MEMC, VIDC, and IOC, an input/output controller and a simple operating system. The Archimedes received a lukewarm response on its launch because personal computing appeared to be consolidating behind the IBM PC standard while Acorn had introduced a computer with a new processor, a new operating system, and no base of software to provide users with the applications they needed.  It took two to three years for a credible amount of applications software native to the ARM and Archimedes to be developed. Since then Acorn has refined and improved its computer models and confirmed its position as a leader in the British home and educational computing market.




 ARM 3 AND ARM2aS   


After the launch of the Archimedes, Acorn continued to support its research and development team in creating improved versions on the chip, offering greater performance. To expand the design so that it offered the kind of performance expected of a high-end personal computer and or workstation, a 4  kbyte on-chip data and instruction cache was added. And in 1989 the ARM3 was launched at the significantly increased clock rate of 25MHz. Acorn's desktop computers using this chip were launch in 1990


A static version of the processor the ARM2aS was developed soon after the ARM3.  This variant added low power consumption to the list of features which made the ARM attractive to developers interested in designing low-cost portable and hand-held devices and electronic personal organizers, and communication device, which although developed as far as working prototypes was never actually marketed.





Interest in the ARM family was growing as more designers became interested in RISC, and the ARM's design was seen to match a definite need for high-performance, low power consumption, low-cost RISC processors.  In conditions of greatest secrecy an agreement was reached between Acorn, VLSI Technology Inc. and a company which had expressed an interest in the for sometime, Apple.  The Acorn RISC Machine became the Advance RISC Machine and the company Advances RICS Machines Ltd was born.  ARM Ltd. was found with a clear mission to continue the development of the ARM processor and to facilitate its use by system developer, whether as a standalone processor. 


ARM Ltd's first development was the next step from the ARM3 processor, which was named ARM6 and included full 32-bit addressing and endedness support.  An improved video controller, VIDC20 was also developed and a floating point processor was also introduced.




As the market for low-cost low power consumption, high performance processors expands, ARM Ltd expanding it global presence by developing relationships with more companies around the world. Since the launch, ARM has developed relationships with more foundries who have licensed and still license its design and sell them in different markets.  From its earliest days with Acorn, ARM Ltd has worked closely with VLSI Technology, Inc., its first partner and the first manufacturer of ARM devices.  In the UK, GEC Plessy Semiconductors was signed as an ARM foundry and partner in January 1992. Plessy now produces a range of ARM standard parts.  It is also the foundry for the ARM250.  In March 1993 Sharp Corporation of Japan signed a deal to manufacture and market ARM processors and associated products. 


ARM Ltd now has offices in California and Japan in order to maintain a close relationship with licensees and their major customers, and to promote existing ARM devices and the company's ability to produce new ones to future customers.  Today ARM continues to establish relationships with new partners like, SUN microsystem and many others, around the world.




In conclusion, from being a single design aimed at a particular project the ARM is now a set of highly customized processors and supporting macrocells suitable for the use in a wide range of applications but targeted at systems requiring high performance from a compact device with low power consumption.