Advanced RISC Machine


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Advanced RISC Machine

(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.

ARM

The most widely used microprocessors worldwide. Designed by ARM Holdings plc, Cambridge, England (www.arm.com), the company was founded in 1990 by Acorn Computers, Apple and VLSI Technology. In 2016, ARM was acquired by Japan-based Softbank. The ARM brand originally stood for Acorn RISC Machine and later Advanced RISC Machine.

ARM chips are 32-bit and 64-bit RISC-based CPUs that are known for their low cost and low power requirements (see RISC). Manufactured under license from ARM by more than a dozen semiconductor companies, billions of ARM-based devices are made every year, including smartphones, tablets, game consoles, e-book readers, netbooks, TVs and myriad other consumer and industrial products.

Very often, an ARM CPU is the processor in a system-on-chip (see SoC). For example, Qualcomm's Snapdragon and NVIDIA's Tegra are ARM-based smartphone and tablet SoCs.

Cortex, SecurCore and StrongARM
ARM processor families are designated by the prefix "ARM" and a digit, such as ARM7, ARM9 and ARM11 or with names such as Cortex and SecurCore, the latter used for secure identification products such as smart cards.

The StrongARM was a high-speed version of the ARM chip that was jointly developed with Digital Equipment Corporation. The SA-100, the first StrongARM chip, was delivered in 1995, and Intel acquired the technology from Digital in 1997. See StrongARM, Thumb and big.LITTLE.
References in periodicals archive ?
Today, Huawei announced the industry's highest-performance Advanced RISC Machine (ARM)-based CPU.
This will be the first time Microsoft will be producing a Windows OS that will work with ARM (Advanced RISC Machine)'s technology which is set to increase the number of chip suppliers, a Bloomberg report said.
Later, in a joint venture with Apple Computer and VLSI Technology, Acorn spun off Advanced RISC Machines, or ARM, as a separate company.

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