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ARM rises from Acorn to lead system-chip revolution

Posted: 28 Nov 2012 ?? ?Print Version ?Bookmark and Share

Keywords:microprocessors? CMOS? processor? Acorn System?

In October 1983 Acorn opted to design its own 32bit addressing processor. Wilson defined the instruction set and Furber worked on the micro-architecture supported by a small but talented team of engineers.

As had been the case in Acorn's previous designs, it was not low power per se so much as simplicity and elegance that drove the design of the Acorn RISC Machine. It was fabbed for Acorn in 3?m CMOS by VLSI Technology Inc. VLSI produced the first ARM silicon on 26 April 1985�and it worked the first time.

One design goal was to have low-latency input/output handling like the 6502. That low latency would stand ARM in good stead for embedded applications later on.

Wilson recalls: "We knew we wanted to put it in a cheap plastic package. We ended up with a design consuming 100-mW that could run off the power of the I/O diodes." That is the charge built up in the ESD-protection I/O diodes could continue to run the processor for some time even after Vcc power had been removed.

The ARM1 had about 25,000 transistors and the follow on ARM2 had about 27,000 transistors. The original aim of an ARM-based computer was achieved in 1987 with the launch of the Acorn Archimedes.

It would be easy to say that the rest is [more recent] history.

But Acorn was not destined to enjoy success in its own name. While its computers continued to enjoy support for a while in the U.K. education market the IBM personal computer revolution - powered initially by the 80286 processor and Microsoft's MSDOS operating system - was a global phenomenon driving almost all before it.

Acorn RISC Machine

Acorn RISC Machine. Fabricated for Acorn by VLSI Technology in 1985 and abbreviated to ARM.

In the late 1980s there were three attempts to spin the processor development business out from Acorn, Wilson said. Eventually in 1990 that was achieved with Apple Computer, and VLSI Technology Inc. backing Advanced Risc Machines Ltd. as a joint venture.

Wilson was not a founder of ARM preferring to stay with Acorn and eventually with DSL chip company Element 14 Ltd. which spun off from Acorn and was sold to Broadcom Corp. in October 2000 for about $600 million. "We did so much more than just the ARM at Acorn including the ARM250 which was the first [ARM-based] system-on-chip design and the ARM7000 and ARM7500FE."

Sophie Wilson did not join ARM but did provide consultancy back to the company. Wilson worked on the ARM7 and the ARM7TDMI and was a consultant on all the ARM processors up to ARM11, but not on the Cortex range.

The ARM processor was low complexity because it had to be easy to design with limited resources, and that made it low power. Its small size made it well suited to the system-chip revolution of the 1990s and it was no accident that it found early success in the mobile phone.

Wilson concludes: "Hermann Hauser says he gave us the things Intel could never give us, no resources, no time and no money."

- Peter Clarke
??EE Times

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