<company> (ARM) A company formed in 1990 by Acorn Computers Ltd., Apple Computer, Inc. and VLSI Technology to market and develop the Advanced RISC Machine microprocessor family, originally designed by Acorn. ARM Ltd. also designs and licenses peripheral chips and supplies supporting software and hardware tools. In April 1993, Nippon Investment and Finance, a Daiwa Securities company, became ARM's fourth investor. In May 1994 Samsung became the sixth large company to have a licence to use the ARM processor core. The success of ARM Ltd. and the strategy to widen the availability of RISC technology has resulted in its chips now being used in a range of products including the {Apple Newton}. As measured by an independent authority, more ARM processors were shipped than SPARC chips in 1993. ARM has also sold three times more chips than the PowerPC consortium. http://systemv.com/armltd/index.html. E-mail: armltd.co.uk. Address: Advanced RISC Machines Ltd. Fulbourn Road, Cherry Hinton, Cambridge CB1 4JN, UK. Telephone: +44 (1223) 400 400. Fax: +44 (1223) 400 410. (1994-11-03)

Advanced RISC Machines Ltd.

<processor> (ARM, Originally Acorn RISC Machine). A series of low-cost, power-efficient 32-bit RISC microprocessors for embedded control, computing, digital signal processing, games, consumer multimedia and portable applications. It was the first commercial RISC microprocessor (or was the {MIPS R2000}?) and was licensed for production by {Asahi Kasei Microsystems}, Cirrus Logic, GEC Plessey Semiconductors, Samsung, Sharp, Texas Instruments and VLSI Technology. The ARM has a small and highly orthogonal instruction set, as do most RISC processors. Every instruction includes a four-bit code which specifies a condition (of the {processor status register}) which must be satisfied for the instruction to be executed. Unconditional execution is specified with a condition "true". Instructions are split into load and store which access memory and arithmetic and logic instructions which work on registers (two source and one destination). The ARM has 27 registers of which 16 are accessible in any particular processor mode. R15 combines the program counter and processor status byte, the other registers are general purpose except that R14 holds the return address after a subroutine call and R13 is conventionally used as a {stack pointer}. There are four processor modes: user, interrupt (with a private copy of R13 and R14), fast interrupt (private copies of R8 to R14) and supervisor (private copies of R13 and R14). The ALU includes a 32-bit barrel-shifter allowing, e.g., a single-cycle shift and add. The first ARM processor, the ARM1 was a prototype which was never released. The ARM2 was originally called the Acorn RISC Machine. It was designed by Acorn Computers Ltd. and used in the original Archimedes, their successor to the {BBC Micro} and BBC Master series which were based on the eight-bit 6502 microprocessor. It was clocked at 8 MHz giving an average performance of 4 - 4.7 MIPS. Development of the ARM family was then continued by a new company, Advanced RISC Machines Ltd. The ARM3 added a fully-associative on-chip cache and some support for multiprocessing. This was followed by the ARM600 chip which was an ARM6 processor core with a 4-kilobyte 64-way set-associative cache, an MMU based on the MEMC2 chip, a write buffer (8 words?) and a coprocessor interface. The ARM7 processor core uses half the power of the ARM6 and takes around half the die size. In a full processor design (ARM700 chip) it should provide 50% to 100% more performance. In July 1994 VLSI Technology, Inc. released the ARM710 processor chip. Thumb is an implementation with reduced code size requirements, intended for embedded applications. An ARM800 chip is also planned. AT&T, IBM, Panasonic, Apple Coputer, Matsushita and Sanyo either rely on, or manufacture, ARM 32-bit processor chips. Usenet newsgroup: news:comp.sys.arm. (1997-08-05)