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ARM Processors

June 24, 2010

In yesterday's article (Dye-Sensitized Solar Cells, June 23, 2010), I wrote about Michael Grätzel's winning of the the 2010 Millennium Technology Prize, a prize that's awarded every second year "...to highlight innovations that assist and enrich our everyday lives...." [1] There are not just winners for this prize, but also runners-up. One runner up and recipient of a 150,000-euro award was Stephen Furber, a professor of computer engineering at the University of Manchester and creator of the ARM family of microprocessors [2].

Photograph of Stephen_Furber

Stephen Furber. (Photo by Peter Howkins.)

The ARM (originally an acronym for the Acorn RISC Machine, and later for the Advanced RISC Machine) is a Reduced Instruction Set Computer. The appellation, "reduced," distinguishes these from their cousin processors, the Complex Instruction Set Computers. I wrote about both classes of processors in a previous article (CISC, RISC, GPU, October 13, 2008). The first stored program computers, such as the DEC PDP-8, which was the first commercial minicomputer, and the ubiquitous Intel X86 processors, are all CISC. What differentiates a RISC machine from a CISC machine is the way data are stored and moved in the CPU. An easy way to identify a RISC architecture is by counting the number of data registers. RISC chips have a lot of registers, and CISC chips have just a few. Other RISC systems are the MIPS and SPARC.

The RISC architecture has two important features. The hardware is simpler than CISC, so it can be added to existing chips without much problem, and the chips consume less power. For these reasons, the 32-bit version of the ARM is used in 98% of cellphones and most handheld electronic devices, such as PDAs, music players and calculators [3]. Furber was quoted by Reuters as saying, "Anywhere I go in the world I get on the train and there are more ARM processors than people, and people using ARM processors." [2]


  1. Website for the Millennium Technology Prize.                                   
  2. Tarmo Virki, "Solar-Cell Inventor Wins Millennium Prize," PCMag.com (June 9, 2010).
  3. ARM Architecture Page on Wikipedia.                                  

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