The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....
Reduced instruction set computing, or RISC , is a CPU design strategy based on the insight that simplified instructions can provide higher performance if this simplicity enables much faster execution of each instruction. A computer based on this strategy is a reduced instruction set computer...
(RISC) instruction set architecture (ISA) developed by ARM Holdings
ARM Holdings
ARM Holdings plc is a British multinational semiconductor and software company headquartered in Cambridge. Its largest business is in processors, although it also designs, licenses and sells software development tools under the RealView and KEIL brands, systems and platforms, system-on-a-chip...
. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit
32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....
ISA in numbers produced. Originally conceived by Acorn Computers
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes...
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
range introduced in 1987.
The relative simplicity of ARM processors makes them suitable for low power applications. As a result, they have become dominant in the mobile and embedded electronics market, as relatively low-cost, small microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s. In 2005, about 98% of the more than one billion mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s sold each year used at least one ARM processor. , ARM processors account for approximately 90% of all embedded 32-bit RISC processors and are used extensively in consumer electronics, including personal digital assistant
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s (PDAs), mobile phones, digital media and music players, hand-held game consoles, calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
s and computer peripherals such as hard drives and routers.
The ARM architecture is licensable. Companies that are current or former ARM licensees include Alcatel-Lucent
Alcatel-Lucent
Alcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...
Broadcom Corporation is a fabless semiconductor company in the wireless and broadband communication business. The company is headquartered in Irvine, California, USA. Broadcom was founded by a professor-student pair Henry Samueli and Henry T. Nicholas III from the University of California, Los...
Cirrus Logic is a fabless semiconductor supplier specializing in analog, mixed-signal, and audio DSP integrated circuits . They are presently headquartered in Austin, Texas. Their audio processors and audio converters are found in many professional audio and consumer entertainment products,...
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
Ember is an American company based in Boston, Massachusetts, USA. Ember has a radio development centre in Cambridge, England, and distributors worldwide. It develops ZigBee wireless networking technology that enables companies involved in energy technologies to help make buildings and homes...
Energy Micro AS is a fabless semiconductor company specializing in 32-bit Flash microcontrollers EFM32 and EFR4D Draco RF Trans-receivers. The semiconductor company focuses on 32-bit microcontrollers with ultra low energy consumption...
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
LG may refer to:*LG Corp., a South Korean electronics and petrochemicals conglomerate*LG Electronics, an affiliate of the South Korean LG Group which produces electronic products* Lawrence Graham, a London headquartered firm of business lawyers...
Marvell is an American producer of storage, communications and consumer semiconductor products.Founded in 1995, Marvell Technology Group Ltd. has operations worldwide and approximately 5,700 employees. Marvell’s U.S. operating subsidiary is based in Santa Clara, California and Marvell has...
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....
is a multinational corporation located in Kyoto, Japan. Founded on September 23, 1889 by Fusajiro Yamauchi, it produced handmade hanafuda cards. By 1963, the company had tried several small niche businesses, such as a cab company and a love hotel....
Nuvoton Technology Corporation is a Taiwan-based semiconductor company established in 2008. It spun off from Winbond Electronics Corp. as a wholly owned subsidiary.-Overview:...
Nvidia is an American global technology company based in Santa Clara, California. Nvidia is best known for its graphics processors . Nvidia and chief rival AMD Graphics Techonologies have dominated the high performance GPU market, pushing other manufacturers to smaller, niche roles...
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
, commonly referred to as OKI, OKI Electric or the OKI Group, is a Japanese company manufacturing and selling info-telecom and printer products. Headquartered in Tokyo, Japan, OKI operates in over 120 countries around the world....
ON Semiconductor , is a semiconductors supplier company. Products include power and signal management, logic, discrete and custom devices for automotive, communications, computing, consumer, industrial, LED lighting, medical, military/aerospace and power applications...
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
is a Japanese multinational corporation that designs and manufactures electronic products. Headquartered in Abeno-ku, Osaka, Japan, Sharp employs more than 55,580 people worldwide as of June 2011. The company was founded in September 1912 and takes its name from one of its founder's first...
STMicroelectronics is an Italian-French electronics and semiconductor manufacturer headquartered in Geneva, Switzerland.While STMicroelectronics corporate headquarters and the headquarters for EMEA region are based in Geneva, the holding company, STMicroelectronics N.V. is registered in Amsterdam,...
Symbios Logic was a manufacturer of SCSI host adapter chipsets and disk array storage subsystems. It was originally established as a division of NCR Corporation in 1972, before NCR's takeover by AT&T in 1991....
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
VLSI Technology, Inc was a company which designed and manufactured custom and semi-custom ICs. The company was based in Silicon Valley, with headquarters at 1109 McKay Drive in San Jose, California...
Yamaha may refer to:* Yamaha Corporation, a Japanese company with a wide range of products and services** Yamaha Motor Company, a Japanese motorized vehicle-producing company...
ZiiLABS is a global technology company, whose ZMS media-rich application processors, reference platforms and enabling software are designed to enable OEMs and ODMs to create products that target a range of low-power consumer electronics and embedded markets, including Android based tablets.-...
.
ARM processors are developed by ARM and by ARM licensees. Prominent ARM processor families developed by ARM Holdings include the ARM7, ARM9, ARM11
ARM11
ARM11 is an ARM architecture 32-bit RISC microprocessor family which introduced the ARMv6 architectural additions. These include SIMD media instructions, multiprocessor support and a new cache architecture...
The ARM Cortex-A8 is a processor core designed by ARM Holdings implementing the ARM v7 instruction set architecture. Compared to the ARM11 core, the Cortex-A8 is dual-issue superscalar, achieving roughly twice the instructions executed per clock cycle....
. Notable ARM processors developed by licensees include AppliedMicro X-Gene DEC
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
The StrongARM is a family of microprocessors that implemented the ARM V4 instruction set architecture . It was developed by Digital Equipment Corporation and later sold to Intel, who continued to manufacture it before replacing it with the XScale....
The i.MX range is a family of Freescale Semiconductor proprietary microprocessors for multimedia applications based on the ARM architecture and focused on low-power consumption. The i.MX application processors are SoCs , that integrate many processing units into one die, like the main CPU, a video...
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
ST-Ericsson is a global wireless platform and semiconductor supplier to four of the top five mobile handset manufacturers. ST-Ericsson is a 50/50 joint venture of Ericsson and STMicroelectronics established on February 3, 2009...
Snapdragon is a family of mobile system on chips by Qualcomm. Qualcomm considers Snapdragon a "platform" for use in smartphones, tablets, and smartbook devices.The Snapdragon application processor core, dubbed Scorpion, is Qualcomm's own design...
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
OMAP product line, the Samsung Hummingbird and the Apple A4
Apple A4
The Apple A4 is a package on package system-on-a-chip designed by Apple and manufactured by Samsung. It combines an ARM Cortex-A8 CPU with a PowerVR GPU, and emphasizes power efficiency. The chip commercially debuted with the release of Apple's iPad tablet; followed shortly by the iPhone 4...
The Apple A5 is a package on package system-on-a-chip designed by Apple and manufactured by Samsung to replace the Apple A4. The chip commercially debuted with the release of Apple's iPad 2 tablet, and also powers the iPhone 4S...
The BBC Microcomputer System, or BBC Micro, was a series of microcomputers and associated peripherals designed and built by Acorn Computers for the BBC Computer Literacy Project, operated by the British Broadcasting Corporation...
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK. These included the Acorn Electron, the BBC Micro, and the Acorn Archimedes...
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
processor to address business markets like the one that would soon be dominated by the IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
The Acorn Business Computer was a series of microcomputers announced at the end of 1983 by the British company Acorn Computers. The series of eight computers was aimed at the business, research and further education markets. However, the ABC range was cancelled before any of the models were...
(ABC) plan required a number of second processors to be made to work with the BBC Micro platform, but processors such as the Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
and National Semiconductor 32016 were unsuitable, and the 6502 was not powerful enough for a graphics based user interface.
Acorn would need a new architecture, having tested all of the available processors and found them wanting. Acorn then seriously considered designing its own processor, and their engineers came across papers on the Berkeley RISC
Berkeley RISC
Berkeley RISC was one of two seminal research projects into RISC-based microprocessor design taking place under ARPA's VLSI project. RISC was led by David Patterson at the University of California, Berkeley between 1980 and 1984, while the other was taking place only a short drive away at Stanford...
project. They felt it showed that if a class of graduate students could create a competitive 32-bit processor, then Acorn would have no problem. A trip to the Western Design Center
Western Design Center
The Western Design Center , located in Mesa, Arizona, USA, is a company developing and manufacturing MOS 65xx-based microprocessors, microcontrollers , and related support chips...
in Phoenix, where the 6502 was being updated by what was effectively a single-person company, showed Acorn engineers Steve Furber
Steve Furber
Professor Stephen Byram Furber CBE, FRS, FREng is the ICL Professor of Computer Engineering at the School of Computer Science at the University of Manchester but is probably best known for his work at Acorn where he was one of the designers of the BBC Micro and the ARM 32-bit RISC...
Sophie Wilson is a British computer scientist. She is known for designing the Acorn Micro-Computer, the first of a long line of computers sold by Acorn Computers Ltd, as well as the instruction set of the highly successful ARM processor.- Life and career :...
that they did not need massive resources and state-of-the-art R&D facilities.
Wilson set about developing the instruction set, writing a simulation of the processor in BBC Basic
BBC BASIC
BBC BASIC is a programming language, developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Sophie Wilson. It is a version of the BASIC programming language adapted for a U.K...
that ran on a BBC Micro with a second 6502 processor. It convinced the Acorn engineers that they were on the right track. Before they could go any further, however, they would need more resources. It was time for Wilson to approach Acorn's CEO, Hermann Hauser
Hermann Hauser
Hermann Maria Hauser, CBE FREng FinstP CPhys , is an entrepreneur who was born in Vienna, Austria but is primarily associated with Silicon Fen in England....
, and explain what was afoot. Once the go-ahead had been given, a small team was put together to implement Wilson's model in hardware.
Acorn RISC Machine: ARM2
The official Acorn RISC Machine project started in October 1983. VLSI Technology, Inc was chosen as silicon partner, since it already supplied Acorn with ROMs and some custom chips. The design was led by Wilson and Furber, with a key design goal of achieving low-latency input/output (interrupt) handling like the 6502. The 6502's memory access architecture had allowed developers to produce fast machines without the use of costly direct memory access
Direct memory access
Direct memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
hardware. VLSI produced the first ARM silicon on 26 April 1985 – it worked the first time and came to be termed ARM1 by April 1985. The first "real" production systems named ARM2 were available the following year.
Its first practical application was as a second processor to the BBC Micro, where it was used to develop the simulation software to finish work on the support chips (VIDC, IOC, MEMC) and to speed up the operation of the CAD software used in developing ARM2. Wilson subsequently coded BBC Basic in ARM assembly language, and the in-depth knowledge obtained from designing the instruction set allowed the code to be very dense, making ARM BBC Basic an extremely good test for any ARM emulator. The original aim of a principally ARM-based computer was achieved in 1987 with the release of the Acorn Archimedes
Acorn Archimedes
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
.
Such was the secrecy surrounding the ARM CPU project that when Olivetti
Olivetti
Olivetti S.p.A. is an Italian manufacturer of computers, printers and other business machines.- Founding :The company was founded as a typewriter manufacturer in 1908 in Ivrea, near Turin, by Camillo Olivetti. The firm was mainly developed by his son Adriano Olivetti...
were negotiating to take a controlling share of Acorn in 1985, they were not told about the development team until after the negotiations had been finalised. In 1992 Acorn once more won the Queen's Award for Technology for the ARM.
The ARM2 featured a 32-bit data bus, a 26-bit address space
Address space
In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.- Overview :...
In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...
. Program code had to lie within the first 64 Mbyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
The program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...
was limited to 24 bits because the top 6 and bottom 2 bits of the 32-bit register served as status flags. The ARM2 was possibly the simplest useful 32-bit microprocessor in the world, with only 30,000 transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s (compare the transistor count with Motorola's six-year older 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
model which was aptly named, since it contained 68,000 transistors). Much of this simplicity comes from not having microcode
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
(which represents about one-quarter to one-third of the 68000) and, like most CPUs of the day, not including any cache
Cache
In computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...
. This simplicity led to its low power usage, while performing better than the Intel 80286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
. A successor, ARM3, was produced with a 4 KB cache, which further improved performance.
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
VLSI Technology, Inc was a company which designed and manufactured custom and semi-custom ICs. The company was based in Silicon Valley, with headquarters at 1109 McKay Drive in San Jose, California...
started working with Acorn on newer versions of the ARM core. The work was so important that Acorn spun off the design team in 1990 into a new company called Advanced RISC Machines Ltd. Advanced RISC Machines became ARM Ltd when its parent company, ARM Holdings plc, floated on the London Stock Exchange
London Stock Exchange
The London Stock Exchange is a stock exchange located in the City of London within the United Kingdom. , the Exchange had a market capitalisation of US$3.7495 trillion, making it the fourth-largest stock exchange in the world by this measurement...
The NASDAQ Stock Market, also known as the NASDAQ, is an American stock exchange. "NASDAQ" originally stood for "National Association of Securities Dealers Automated Quotations". It is the second-largest stock exchange by market capitalization in the world, after the New York Stock Exchange. As of...
in 1998.
The new Apple-ARM work would eventually turn into the ARM6, first released in early 1992. Apple used the ARM6-based ARM 610 as the basis for their Apple Newton
Apple Newton
The MessagePad was the first series of personal digital assistant devices developed by Apple for the Newton platform in 1993. Some electronic engineering and the manufacture of Apple's MessagePad devices was done in Japan by the Sharp Corporation...
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
The RiscPC was Acorn Computers's next generation RISC OS/Acorn RISC Machine computer, launched on 15 April 1994, which superseded the Acorn Archimedes. The Acorn PC card and software allows PC compatible software to be run....
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
licensed the ARM6 architecture and produced the StrongARM
StrongARM
The StrongARM is a family of microprocessors that implemented the ARM V4 instruction set architecture . It was developed by Digital Equipment Corporation and later sold to Intel, who continued to manufacture it before replacing it with the XScale....
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
(more recent versions draw far less). This work was later passed to Intel as a part of a lawsuit settlement, and Intel took the opportunity to supplement their aging i960
Intel i960
Intel's i960 was a RISC-based microprocessor design that became popular during the early 1990s as an embedded microcontroller, becoming a best-selling CPU in that field, along with the competing AMD 29000...
line with the StrongARM. Intel later developed its own high performance implementation named XScale
Intel XScale
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
Marvell is an American producer of storage, communications and consumer semiconductor products.Founded in 1995, Marvell Technology Group Ltd. has operations worldwide and approximately 5,700 employees. Marvell’s U.S. operating subsidiary is based in Santa Clara, California and Marvell has...
.
Licensing
The ARM core has remained largely the same size throughout these changes. ARM2 had 30,000 transistors, while the ARM6 grew to only 35,000. ARM's business has always been to sell IP cores, which licensees use to create microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s and CPUs based on this core. The most successful implementation has been the ARM7TDMI
ARM7TDMI
ARM7 is a generation of ARM processor designs. This generation introduced the Thumb 16-bit instruction set providing improved code density compared to previous designs. The most widely used ARM7 designs implement the ARMv4T architecture, but some implement ARMv3 or ARMv5TEJ...
An original design manufacturer is a company which designs and manufactures a product which is specified and eventually branded by another firm for sale. Such companies allow the brand firm to produce without having to engage in the organization or running of a factory...
combines the ARM core with a number of optional parts to produce a complete CPU, one that can be built on old semiconductor fabs and still deliver substantial performance at a low cost. Atmel
Atmel
Atmel Corporation is a manufacturer of semiconductors, founded in 1984. Its focus is on system-level solutions built around flash microcontrollers...
has been a precursor design center in the ARM7TDMI-Based Embedded System.
ARM licensed about 1.6 billion cores in 2005. In 2005, about 1 billion ARM cores went into mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s. By January 2008, over 10 billion ARM cores had been built, and in 2008 iSuppli predicted that by 2011, 5 billion ARM cores will be shipping per year. , ARM states that over 15 billion ARM processors have shipped.
A smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera...
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s and other mobile devices range from ARMv5, in obsolete/low-end devices, to the ARM M-series, in current high-end devices. XScale
XScale
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
and ARM926 processors are ARMv5TE, and are now more numerous in high-end devices than the StrongARM
StrongARM
The StrongARM is a family of microprocessors that implemented the ARM V4 instruction set architecture . It was developed by Digital Equipment Corporation and later sold to Intel, who continued to manufacture it before replacing it with the XScale....
ARM7 is a generation of ARM processor designs. This generation introduced the Thumb 16-bit instruction set providing improved code density compared to previous designs. The most widely used ARM7 designs implement the ARMv4T architecture, but some implement ARMv3 or ARMv5TEJ...
based ARMv4 processors, but lower-end devices may use older cores with lower licensing costs. ARMv6 processors represented a step up in performance from standard ARMv5 cores, and are used in some cases, but Cortex processors (ARMv7) now provide faster and more power-efficient options than all those prior generations. Cortex-A targets applications processors, as needed by smartphones that formerly used ARM9 or ARM11. Cortex-R targets real-time applications, and Cortex-M targets microcontrollers.
In 2009, some manufacturers introduced netbooks based on ARM architecture CPUs, in direct competition with netbooks based on Intel Atom
Intel Atom
Intel Atom is the brand name for a line of ultra-low-voltage x86 and x86-64 CPUs from Intel, designed in 45 nm CMOS and used mainly in netbooks, nettops, embedded application ranging from health care to advanced robotics and Mobile Internet devices...
.
According to analyst firm IHS iSuppli, by 2015, ARM ICs are estimated to be in 23% of all laptops.
In 2011, HiSilicon Technologies Co. Ltd. licensed a variety of ARM technology to be used in communications chip designs. These included 3G/4G basestations, networking infrastructure and mobile computing applications.
ARM cores
Architecture
Family
ARMv1
ARM1
ARMv2
ARM2, ARM3
ARMv3
ARM6, ARM7
ARMv4
StrongARM, ARM7TDMI, ARM9TDMI
ARMv5
ARM7EJ, ARM9E, ARM10E, XScale
ARMv6
ARM11
ARMv7
Cortex
ARMv8
No cores available yet. Will support 64-bit data and addressing
A summary of the numerous vendors who implement ARM cores in their design is provided by ARM.
Example applications of ARM cores
ARM cores are used in a number of products, particularly various smartphone
Smartphone
A smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera...
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
The iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and...
The ASUS Eee Pad Transformer is an Android 3.2 Honeycomb tablet computer announced at CES 2011 and launched on March 30, 2011. The Transformer design includes an optional docking keyboard.- Features :...
iPod is a line of portable media players created and marketed by Apple Inc. The product line-up currently consists of the hard drive-based iPod Classic, the touchscreen iPod Touch, the compact iPod Nano, and the ultra-compact iPod Shuffle...
portable media player, Canon PowerShot A470 digital camera, Nintendo DS
Nintendo DS
The is a portable game console produced by Nintendo, first released on November 21, 2004. A distinctive feature of the system is the presence of two separate LCD screens, the lower of which is a touchscreen, encompassed within a clamshell design, similar to the Game Boy Advance SP...
TomTom NV is a Dutch manufacturer of automotive navigation systems, including both stand-alone units and software for personal digital assistants and mobile telephones. It is the leading manufacturer of navigation systems in Europe. TomTom's customer service is located in Amsterdam, Netherlands...
automotive navigation system.
Since 2005, ARM was also involved in Manchester University's computer, SpiNNaker, which used ARM cores to simulate the human brain.
Architecture
From 1995 onwards, the ARM Architecture Reference Manual has been the primary source of documentation on the ARM processor architecture and instruction set, distinguishing interfaces that all ARM processors are required to support (such as instruction semantics) from implementation details that may vary. The architecture has evolved over time, and starting with the Cortex series of cores, three "profiles" are defined:
"Application" profile: Cortex-A series
"Real-time" profile: Cortex-R series
"Microcontroller" profile: Cortex-M series
Profiles are allowed to subset the architecture. For example the ARMv7-M profile used by the Cortex-M3 core is notable in that it supports only the Thumb-2 instruction set, and the ARMv6-M profile (used by the Cortex-M0) is a subset of the ARMv7-M profile (supporting fewer instructions).
Instruction set
To keep the design clean, simple and fast, the original ARM implementation was hardwired without microcode
Microcode
Microcode is a layer of hardware-level instructions and/or data structures involved in the implementation of higher level machine code instructions in many computers and other processors; it resides in special high-speed memory and translates machine instructions into sequences of detailed...
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
processor used in prior Acorn microcomputers.
The ARM architecture includes the following RISC features:
Load/store architecture.
No support for misaligned memory accesses (now supported in ARMv6 cores, with some exceptions related to load/store multiple word instructions).
A register file is an array of processor registers in a central processing unit . Modern integrated circuit-based register files are usually implemented by way of fast static RAMs with multiple ports...
.
Fixed instruction width of 32 bits to ease decoding and pipelining, at the cost of decreased code density. Later, the Thumb instruction set increased code density.
Mostly single-cycle execution.
To compensate for the simpler design, compared with contemporary processors like the Intel 80286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
The Motorola 68020 is a 32-bit microprocessor from Motorola, released in 1984. It is the successor to the Motorola 68010 and is succeeded by the Motorola 68030...
, some additional design features were used:
Conditional execution of most instructions, reducing branch overhead and compensating for the lack of a branch predictor
Branch predictor
In computer architecture, a branch predictor is a digital circuit that tries to guess which way a branch will go before this is known for sure. The purpose of the branch predictor is to improve the flow in the instruction pipeline...
.
Arithmetic instructions alter condition codes only when desired.
A barrel shifter is a digital circuit that can shift a data word by a specified number of bits in one clock cycle. It can be implemented as a sequence of multiplexers , and in such an implementation the output of one mux is connected to the input of the next mux in a way that depends on the shift...
which can be used without performance penalty with most arithmetic instructions and address calculations.
Addressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...
A link register, in many instruction set architectures such as the PowerPC, ARM, and the PA-RISC, is a special purpose register which holds the address to return to when a function call completes...
In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
subsystem with switched register banks.
Conditional execution
The conditional execution feature (called predication
Branch predication
Branch predication is a strategy in computer architecture design for mitigating the costs usually associated with conditional branches, particularly branches to short sections of code...
) is implemented with a 4-bit condition code selector (the predicate) on every instruction; one of the four-bit codes is reserved as an "escape code" to specify certain unconditional instructions, but nearly all common instructions are conditional. Most CPU architectures only have condition codes on branch instructions.
This cuts down significantly on the encoding bits available for displacements in memory access instructions, but on the other hand it avoids branch instructions when generating code for small if statements. The standard example of this is the subtraction-based Euclidean algorithm
Euclidean algorithm
In mathematics, the Euclidean algorithm is an efficient method for computing the greatest common divisor of two integers, also known as the greatest common factor or highest common factor...
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, the loop is:
while(i != j) {
if (i > j)
i -= j;
else
j -= i;
}
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
, the loop is:
loop CMP Ri, Rj ; set condition "NE" if (i != j),
; "GT" if (i > j),
; or "LT" if (i < j)
SUBGT Ri, Ri, Rj ; if "GT" (greater than), i = i-j;
SUBLT Rj, Rj, Ri ; if "LT" (less than), j = j-i;
BNE loop ; if "NE" (not equal), then loop
which avoids the branches around the then and else clauses.
Note that if Ri and Rj are equal then neither of the SUB instructions will be executed, optimising out the need for a conditional branch to implement the while check at the top of the loop, for example had SUBLE (less than or equal) been used.
One of the ways that Thumb code provides a more dense encoding is to remove that four bit selector from non-branch instructions.
Other features
Another feature of the instruction set is the ability to fold shifts and rotates into the "data processing" (arithmetic, logical, and register-register move) instructions, so that, for example, the C statement a += (j << 2);
could be rendered as a single-word, single-cycle instruction on the ARM. ADD Ra, Ra, Rj, LSL #2
This results in the typical ARM program being denser than expected with fewer memory accesses; thus the pipeline is used more efficiently. Even though the ARM runs at what many would consider to be low speeds, it nevertheless competes quite well with much more complex CPU designs.
The ARM processor also has some features rarely seen in other RISC architectures, such as PC
Program counter
The program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...
-relative addressing (indeed, on the 32-bit ARM the PC
Program counter
The program counter , commonly called the instruction pointer in Intel x86 microprocessors, and sometimes called the instruction address register, or just part of the instruction sequencer in some computers, is a processor register that indicates where the computer is in its instruction sequence...
is one of its 16 registers) and pre- and post-increment addressing modes.
Another item of note is that the ARM has been around for a while, with the instruction set increasing somewhat over time. Some early ARM processors (before ARM7TDMI), for example, have no instruction to store a two-byte quantity, thus, strictly speaking, for them it's not possible to generate efficient code that would behave the way one would expect for C objects of type "int16_t".
Pipelines and other implementation issues
The ARM7 and earlier implementations have a three stage pipeline; the stages being fetch, decode, and execute. Higher performance designs, such as the ARM9, have deeper pipelines: Cortex-A8 has thirteen stages. Additional implementation changes for higher performance include a faster adder, and more extensive branch prediction logic. The difference between the ARM7DI and ARM7DMI cores, for example, was an improved multiplier (hence the added "M").
Coprocessors
For those familiar with the Intel x86 family of CPUs, the ARM family of processors does not support or have any instructions similar to CPUID
CPUID
The CPUID opcode is a processor supplementary instruction for the x86 architecture. It was introduced by Intel in 1993 when it introduced the Pentium and SL-Enhanced 486 processors....
. There are however mechanisms for addressing coprocessors in the ARM architecture.
The ARM architecture provides a non-intrusive way of extending the instruction set using "coprocessors" which can be addressed using MCR, MRC, MRRC, MCRR, and similar instructions. The coprocessor space is divided logically into 16 coprocessors with numbers from 0 to 15, coprocessor 15 (cp15) being reserved for some typical control functions like managing the caches and MMU
Memory management unit
A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...
operation (on processors that have one).
In ARM-based machines, peripheral devices are usually attached to the processor by mapping their physical registers into ARM memory space or into the coprocessor space or connecting to another device (a bus) which in turn attaches to the processor. Coprocessor accesses have lower latency so some peripherals (for example XScale
XScale
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
interrupt controller) are designed to be accessible in both ways (through memory and through coprocessors).
In other cases, chip designers only integrate hardware using the coprocessor mechanism. For example, an image processing engine might be a small ARM7TDMI core combined with a coprocessor that has specialized operations to support a specific set of HDTV transcoding primitives.
Debugging
All modern ARM processors include hardware debugging facilities; without them, software debuggers could not perform basic operations like halting, stepping, and breakpointing of code starting from reset. These facilities are built using JTAG
JTAG
Joint Test Action Group is the common name for what was later standardized as the IEEE 1149.1 Standard Test Access Port and Boundary-Scan Architecture. It was initially devised for testing printed circuit boards using boundary scan and is still widely used for this application.Today JTAG is also...
support, though some newer cores optionally support ARM's own two-wire "SWD" protocol. In ARM7TDMI cores, the "D" represented JTAG debug support, and the "I" represented presence of an "EmbeddedICE" debug module. For ARM7 and ARM9 core generations, EmbeddedICE over JTAG was a de-facto debug standard, although it was not architecturally guaranteed.
The ARMv7 architecture defines basic debug facilities at an architectural level. These include breakpoints, watchpoints, and instruction execution in a "Debug Mode"; similar facilities were also available with EmbeddedICE. Both "halt mode" and "monitor" mode debugging are supported. The actual transport mechanism used to access the debug facilities is not architecturally specified, but implementations generally include JTAG support.
There is a separate ARM "CoreSight" debug architecture, which is not architecturally required by ARMv7 processors.
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
and multimedia applications, a few new instructions were added to the set. These are signified by an "E" in the name of the ARMv5TE and ARMv5TEJ architectures. E-variants also imply T,D,M and I.
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
architectures. They are variations on signed multiply–accumulate, saturated add and subtract, and count leading zeros.
Jazelle
Jazelle is a technique that allows Java Bytecode to be executed directly in the ARM architecture as a third execution state (and instruction set) alongside the existing ARM and Thumb-mode. Support for this state is signified by the "J" in the ARMv5TEJ architecture, and in ARM9EJ-S and ARM7EJ-S core names. Support for this state is required starting in ARMv6 (except for the ARMv7-M profile), although newer cores only include a trivial implementation that provides no hardware acceleration.
Thumb
To improve compiled code-density, processors since the ARM7TDMI have featured the Thumb instruction set state. (The "T" in "TDMI" indicates the Thumb feature.) When in this state, the processor executes the Thumb instruction set, a compact 16-bit encoding for a subset of the ARM instruction set. Most of the Thumb instructions are directly mapped to normal ARM instructions. The space-saving comes from making some of the instruction operands implicit and limiting the number of possibilities compared to the ARM instructions executed in the ARM instruction set state.
In Thumb, the 16-bit opcodes have less functionality. For example, only branches can be conditional, and many opcodes are restricted to accessing only half of all of the CPU's general purpose registers. The shorter opcodes give improved code density overall, even though some operations require extra instructions. In situations where the memory port or bus width is constrained to less than 32 bits, the shorter Thumb opcodes allow increased performance compared with 32-bit ARM code, as less program code may need to be loaded into the processor over the constrained memory bandwidth.
The is a 32-bit handheld video game console developed, manufactured, and marketed by Nintendo. It is the successor to the Game Boy Color. It was released in Japan on March 21, 2001; in North America on June 11, 2001; in Australia and Europe on June 22, 2001; and in the People's Republic of China...
, typically have a small amount of RAM accessible with a full 32-bit datapath; the majority is accessed via a 16 bit or narrower secondary datapath. In this situation, it usually makes sense to compile Thumb code and hand-optimise a few of the most CPU-intensive sections using full 32-bit ARM instructions, placing these wider instructions into the 32-bit bus accessible memory.
The first processor with a Thumb instruction decoder was the ARM7TDMI. All ARM9 and later families, including XScale
Intel XScale
The XScale, a microprocessor core, is Intel's and Marvell's implementation of the ARMv5 architecture, and consists of several distinct families: IXP, IXC, IOP, PXA and CE . Intel sold the PXA family to Marvell Technology Group in June 2006....
, have included a Thumb instruction decoder.
Thumb-2
Thumb-2 technology made its debut in the ARM1156 core, announced in 2003. Thumb-2 extends the limited 16-bit instruction set of Thumb with additional 32-bit instructions to give the instruction set more breadth, thus producing a variable-length instruction set. A stated aim for Thumb-2 is to achieve code density similar to Thumb with performance similar to the ARM instruction set on 32-bit memory. In ARMv7 this goal can be said to have been met.
Thumb-2 extends both the ARM and Thumb instruction set with yet more instructions, including bit-field manipulation, table branches, and conditional execution. A new "Unified Assembly Language" (UAL) supports generation of either Thumb-2 or ARM instructions from the same source code; versions of Thumb seen on ARMv7 processors are essentially as capable as ARM code (including the ability to write interrupt handlers). This requires a bit of care, and use of a new "IT" (if-then) instruction, which permits up to four successive instructions to execute based on a tested condition. When compiling into ARM code this is ignored, but when compiling into Thumb-2 it generates an actual instruction. For example:
if (r0 r1)
CMP r0, r1
ITE EQ ; ARM: no code ... Thumb: IT instruction
then r0 = r2;
MOVEQ r0, r2 ; ARM: conditional; Thumb: condition via ITE 'T' (then)
else r0 = r3;
MOVNE r0, r3 ; ARM: conditional; Thumb: condition via ITE 'E' (else)
recall that the Thumb MOV instruction has no bits to encode "EQ" or "NE"
All ARMv7 chips support the Thumb-2 instruction set.
Some chips, such as the Cortex-M3, support only the Thumb-2 instruction set. Other chips in the Cortex and ARM11 series support both "ARM instruction set mode" and "Thumb-2 instruction set mode".
Thumb Execution Environment (ThumbEE)
ThumbEE, also termed Thumb-2EE, and marketed as Jazelle RCT (Runtime Compilation Target), was announced in 2005, first appearing in the Cortex-A8 processor. ThumbEE is a fourth processor mode, making small changes to the Thumb-2 extended Thumb instruction set. These changes make the instruction set particularly suited to code generated at runtime (e.g. by JIT compilation
Just-in-time compilation
In computing, just-in-time compilation , also known as dynamic translation, is a method to improve the runtime performance of computer programs. Historically, computer programs had two modes of runtime operation, either interpreted or static compilation...
) in managed Execution Environments. ThumbEE is a target for languages such as Limbo, Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
, and allows JIT compilers to output smaller compiled code without impacting performance.
New features provided by ThumbEE include automatic null pointer checks on every load and store instruction, an instruction to perform an array bounds check, access to registers r8-r15 (where the Jazelle/DBX Java VM state is held), and special instructions that call a handler. Handlers are small sections of frequently called code, commonly used to implement a feature of a high level language, such as allocating memory for a new object. These changes come from repurposing a handful of opcodes, and knowing the core is in the new ThumbEE mode.
VFP
VFP (Vector Floating Point) technology is an FPU coprocessor extension to the ARM architecture. It provides low-cost single-precision
Single precision floating-point format
Single-precision floating-point format is a computer number format that occupies 4 bytes in computer memory and represents a wide dynamic range of values by using a floating point....
and double-precision floating-point computation fully compliant with the ANSI/IEEE Std 754-1985 Standard for Binary Floating-Point Arithmetic. VFP provides floating-point computation suitable for a wide spectrum of applications such as PDAs, smartphones, voice compression and decompression, three-dimensional graphics and digital audio, printers, set-top boxes, and automotive applications. The VFP architecture was intended to support execution of short "vector mode" instructions but these operated on each vector element sequentially and thus did not offer the performance of true single instruction, multiple data
SIMD
Single instruction, multiple data , is a class of parallel computers in Flynn's taxonomy. It describes computers with multiple processing elements that perform the same operation on multiple data simultaneously...
(SIMD) vector parallelism. This vector mode was therefore removed shortly after its introduction, to be replaced with the much more powerful NEON Advanced SIMD unit.
Some devices such as the ARM Cortex-A8 has a cut-down VFPLite module instead of a full VFP module, and requires roughly 10x more clock cycles per float operation. Other floating-point and/or SIMD coprocessors found in ARM-based processors include FPA, FPE, iwMMXt. They provide some of the same functionality as VFP but are not opcode
Opcode
In computer science engineering, an opcode is the portion of a machine language instruction that specifies the operation to be performed. Their specification and format are laid out in the instruction set architecture of the processor in question...
-compatible with it.
Advanced SIMD (NEON)
The Advanced SIMD extension (aka NEON or "MPE" Media Processing Engine) is a combined 64- and 128-bit single instruction multiple data
SIMD
Single instruction, multiple data , is a class of parallel computers in Flynn's taxonomy. It describes computers with multiple processing elements that perform the same operation on multiple data simultaneously...
(SIMD) instruction set that provides standardized acceleration for media and signal processing applications. NEON is included in all Cortex-A8 devices (such as the iPhone 4) but is optional in Cortex-A9 devices (such as the iPhone 4S). NEON can execute MP3 audio decoding on CPUs running at 10 MHz and can run the GSM adaptive multi-rate (AMR) speech codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
at no more than 13 MHz. It features a comprehensive instruction set, separate register files and independent execution hardware. NEON supports 8-, 16-, 32- and 64-bit integer and single-precision (32-bit) floating-point data and operates in SIMD operations for handling audio and video processing as well as graphics and gaming processing. In NEON, the SIMD supports up to 16 operations at the same time. The NEON hardware shares the same floating-point registers as used in VFP. Devices such as the ARM Cortex-A8 and Cortex-A9 support 128-bit vectors but will execute with just 64-bits at a time, whereas newer Cortex-A15 devices can execute 128-bits at once.
Security Extensions (TrustZone)
The Security Extensions, marketed as TrustZone Technology, is found in ARMv6KZ and later application profile architectures. It provides a low cost alternative to adding an additional dedicated security core to an SoC
System-on-a-chip
A system on a chip or system on chip is an integrated circuit that integrates all components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on a single chip substrate...
, by providing two virtual processors backed by hardware based access control. This enables the application core to switch between two states, referred to as worlds (to reduce confusion with other names for capability domains), in order to prevent information from leaking from the more trusted world to the less trusted world. This world switch is generally orthogonal to all other capabilities of the processor, thus each world can operate independently of the other while using the same core. Memory and peripherals are then made aware of the operating world of the core and may use this to provide access control to secrets and code on the device.
Typical applications of TrustZone Technology are to run a rich operating system in the less trusted world, and smaller security-specialized code in the more trusted world (named TrustZone Software, a TrustZone optimized version of the Trusted Foundations Software developed by Trusted Logic), allowing much tighter digital rights management
Digital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
for controlling the use of media on ARM-based devices, and preventing any unapproved use of the device.
In practice, since the specific implementation details of TrustZone are proprietary and have not been publicly disclosed for review, it is unclear what level of assurance is provided for a given threat model.
The NX bit, which stands for No eXecute, is a technology used in CPUs to segregate areas of memory for use by either storage of processor instructions or for storage of data, a feature normally only found in Harvard architecture processors...
, which is referred to as XN, for eXecute Never.
ARM licensees
ARM Ltd does not manufacture and sell CPU devices based on its own designs, but rather, licenses the processor architecture to interested parties. ARM offers a variety of licensing terms, varying in cost and deliverables. To all licensees, ARM provides an integratable hardware description of the ARM core, as well as complete software development toolset (compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
A debugger or debugging tool is a computer program that is used to test and debug other programs . The code to be examined might alternatively be running on an instruction set simulator , a technique that allows great power in its ability to halt when specific conditions are encountered but which...
, SDK), and the right to sell manufactured silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
containing the ARM CPU.
Fabless licensees, who wish to integrate an ARM core into their own chip design, are usually only interested in acquiring a ready-to-manufacture verified IP core. For these customers, ARM delivers a gate netlist
Netlist
The word netlist can be used in several different contexts, but perhaps the most popular is in the field of electronic design. In this context, a "netlist" describes the connectivity of an electronic design....
description of the chosen ARM core, along with an abstracted simulation model and test programs to aid design integration and verification. More ambitious customers, including integrated device manufacturers (IDM) and foundry operators, choose to acquire the processor IP in synthesizable
Logic synthesis
In electronics, logic synthesis is a process by which an abstract form of desired circuit behavior, typically register transfer level , is turned into a design implementation in terms of logic gates. Common examples of this process include synthesis of HDLs, including VHDL and Verilog...
In the semiconductor and electronic design industry, Verilog is a hardware description language used to model electronic systems. Verilog HDL, not to be confused with VHDL , is most commonly used in the design, verification, and implementation of digital logic chips at the register-transfer level...
) form. With the synthesizable RTL, the customer has the ability to perform architectural level optimizations and extensions. This allows the designer to achieve exotic design goals not otherwise possible with an unmodified netlist (high clock speed, very low power consumption, instruction set extensions, etc.). While ARM does not grant the licensee the right to resell the ARM architecture itself, licensees may freely sell manufactured product (chip devices, evaluation boards, complete systems, etc.). Merchant
Merchant
A merchant is a businessperson who trades in commodities that were produced by others, in order to earn a profit.Merchants can be one of two types:# A wholesale merchant operates in the chain between producer and retail merchant...
foundries can be a special case; not only are they allowed to sell finished silicon containing ARM cores, they generally hold the right to re-manufacture ARM cores for other customers.
Like most IP vendors, ARM prices its IP based on perceived value. In architectural terms, lower performing ARM cores command lower license costs than higher performing cores. In implementation terms, a synthesizable core costs more than a hard macro (blackbox) core. Complicating price matters, a merchant foundry which holds an ARM license (such as Samsung and Fujitsu) can offer reduced licensing costs to its fab customers. In exchange for acquiring the ARM core through the foundry's in-house design services, the customer can reduce or eliminate payment of ARM's upfront license fee. Compared to dedicated semiconductor foundries (such as TSMC
TSMC
Taiwan Semiconductor Manufacturing Company, Limited or TSMC is the world's largest dedicated independent semiconductor foundry, with its headquarters and main operations located in the Hsinchu Science Park in Hsinchu, Taiwan.-Overview:...
UMC was founded as Taiwan's first semiconductor company in 1980 as a spin-off of the government-sponsored Industrial Technology Research Institute .-Overview:...
) without in-house design services, Fujitsu/Samsung charge 2 to 3 times more per manufactured wafer. For low to mid volume applications, a design service foundry offers lower overall pricing (through subsidization of the license fee). For high volume mass produced parts, the long term cost reduction achievable through lower wafer pricing reduces the impact of ARM's NRE (Non-Recurring Engineering) costs, making the dedicated foundry a better choice.
Many semiconductor or IC design firms hold ARM licenses; Analog Devices
Analog Devices
Analog Devices, Inc. , known as ADI, is an American multinational semiconductor company specializing in data conversion and signal conditioning technology, headquartered in Norwood, Massachusetts...
Broadcom Corporation is a fabless semiconductor company in the wireless and broadband communication business. The company is headquartered in Irvine, California, USA. Broadcom was founded by a professor-student pair Henry Samueli and Henry T. Nicholas III from the University of California, Los...
Cirrus Logic is a fabless semiconductor supplier specializing in analog, mixed-signal, and audio DSP integrated circuits . They are presently headquartered in Austin, Texas. Their audio processors and audio converters are found in many professional audio and consumer entertainment products,...
Energy Micro AS is a fabless semiconductor company specializing in 32-bit Flash microcontrollers EFM32 and EFR4D Draco RF Trans-receivers. The semiconductor company focuses on 32-bit microcontrollers with ultra low energy consumption...
Faraday Technology is a turnkey application-specific IC and silicon intellectual property provider headquartered in Taiwan, with a network of sales and research offices in the United States, Japan, Europe, and China....
is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
Infineon Technologies AG is a German semiconductor manufacturer and was founded on April 1, 1999, when the semiconductor operations of the parent company Siemens AG were spun off to form a separate legal entity. , Infineon has 25,149 employees worldwide...
Marvell is an American producer of storage, communications and consumer semiconductor products.Founded in 1995, Marvell Technology Group Ltd. has operations worldwide and approximately 5,700 employees. Marvell’s U.S. operating subsidiary is based in Santa Clara, California and Marvell has...
is a multinational corporation located in Kyoto, Japan. Founded on September 23, 1889 by Fusajiro Yamauchi, it produced handmade hanafuda cards. By 1963, the company had tried several small niche businesses, such as a cab company and a love hotel....
, commonly referred to as OKI, OKI Electric or the OKI Group, is a Japanese company manufacturing and selling info-telecom and printer products. Headquartered in Tokyo, Japan, OKI operates in over 120 countries around the world....
Qualcomm is an American global telecommunication corporation that designs, manufactures and markets digital wireless telecommunications products and services based on its code division multiple access technology and other technologies. Headquartered in San Diego, CA, USA...
is a Japanese multinational corporation that designs and manufactures electronic products. Headquartered in Abeno-ku, Osaka, Japan, Sharp employs more than 55,580 people worldwide as of June 2011. The company was founded in September 1912 and takes its name from one of its founder's first...
STMicroelectronics is an Italian-French electronics and semiconductor manufacturer headquartered in Geneva, Switzerland.While STMicroelectronics corporate headquarters and the headquarters for EMEA region are based in Geneva, the holding company, STMicroelectronics N.V. is registered in Amsterdam,...
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
are some of the many companies who have licensed the ARM in one form or another.
Approximate licensing costs
ARM's 2006 annual report and accounts state that royalties totalling £88.7 million ($164.1 million) were the result of licensees shipping 2.45 billion units. This is equivalent to £0.036 ($0.067) per unit shipped. However, this is averaged across all cores, including expensive new cores and inexpensive older cores.
In the same year ARM's licensing revenues for processor cores were £65.2 million (US$119.5 million), in a year when 65 processor licenses were signed, an average of £1 million ($1.84 million) per license. Again, this is averaged across both new and old cores.
Given that ARM's 2006 income from processor cores was approximately 60% from royalties and 40% from licenses, ARM makes the equivalent of £0.06 ($0.11) per unit shipped including both royalties and licenses. However, as one-off licenses are typically bought for new technologies, unit sales (and hence royalties) are dominated by more established products. Hence, the figures above do not reflect the true costs of any single ARM product.
Operating systems
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...
personal computers ran an interim operating system called Arthur, which evolved into RISC OS
RISC OS
RISC OS is a computer operating system originally developed by Acorn Computers Ltd in Cambridge, England for their range of desktop computers, based on their own ARM architecture. First released in 1987, under the name Arthur, the subsequent iteration was renamed as in 1988...
, used on later ARM-based systems from Acorn and other vendors.
Embedded operating systems
The ARM architecture is supported by a large number of embedded
Embedded operating system
An embedded operating system is an operating system for embedded computer systems. These operating systems are designed to be compact, efficient, and reliable, forsaking many functions that non-embedded computer operating systems provide, and which may not be used by the specialized applications...
and real-time operating systems, including Windows CE
Windows CE
Microsoft Windows CE is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows...
The .NET Micro Framework is an Open Source .NET platform for resource-constrained devices with at least 256 KBytes of flash and 64 KBytes of RAM. It includes a small version of the .NET CLR and supports development in C#, Visual Basic .NET, and debugging using Microsoft Visual Studio...
Symbian is a mobile operating system and computing platform designed for smartphones and currently maintained by Accenture. The Symbian platform is the successor to Symbian OS and Nokia Series 60; unlike Symbian OS, which needed an additional user interface system, Symbian includes a user...
FreeRTOS is a real-time operating system for embedded devices, being ported to several microcontrollers. It is distributed under the GPL with an optional exception...
eCos is an open source, royalty-free, real-time operating system intended for embedded systems and applications which need only one process with multiple threads. It is designed to be customizable to precise application requirements of run-time performance and hardware needs...
INTEGRITY is a real-time operating system produced and marketed by Green Hills Software. It is royalty-free, POSIX-certified, and intended for use in embedded systems needing reliability, availability, and fault tolerance. It is built atop the velOSity microkernel and is intended mainly for modern...
Nucleus OS is a real-time operating system and toolset created by the Embedded Systems Division of Mentor Graphics for various central processing unit platforms. Nucleus OS is an embedded software solution and is in an estimated 2.11 billion devices worldwide.Development is typically done on a...
MicroC/OS-II , is a low-cost priority-based pre-emptive real-time multitasking operating system kernel for microprocessors, written mainly in the C programming language...
QNX is a commercial Unix-like real-time operating system, aimed primarily at the embedded systems market. The product was originally developed by Canadian company, QNX Software Systems, which was later acquired by Canadian BlackBerry-producer Research In Motion.-Description:As a microkernel-based...
RTXC Quadros is a real time operating system written mainly in the C programming language. It is mainly intended for use in embedded systems.The RTXC RTOS was originally developed by AT Barrett and Associates in the 1970s. It is currently maintained by Quadros Systems, Inc...
ThreadX, developed and marketed by Express Logic, Inc. of San Diego, California, USA, is a real-time operating system . Similar RTOSes are available from other vendors such as VxWorks, Nucleus RTOS, OSE, QNX, LynxOS, etc...
The Unison Operating System is a real-time operating system optimized for system-on-a-chip , multi-core and digital signal processor systems. It is open source. It offers Linux compatibility while being much smaller than Linux...
VxWorks is a real-time operating system developed as proprietary software by Wind River Systems of Alameda, California, USA. First released in 1987, VxWorks is designed for use in embedded systems.- History :...
MQX RTOS is a real-time operating system developed by Precise Software Technologies Inc., and currently sold by ARC International, Embedded Access Inc, and Freescale....
The Operating System Embedded is a real-time embedded operating system created by the Swedish information technology company ENEA AB. Bengt Eliasson, who at the time was a consultant from ENEA with an assignment at Ericsson, wrote the basic parts of the kernel...
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
iOS is an operating system for iPad, iPhone, iPod Touch, and Apple TV.IOS may also refer to:-Companies and organisations:* Illinois Ornithological Society, American state-based bird club...
Plan 9 from Bell Labs is a distributed operating system. It was developed primarily for research purposes as the successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002...
Inferno is a distributed operating system started at Bell Labs, but is now developed and maintained by Vita Nuova Holdings as free software. Inferno was based on the experience gained with Plan 9 from Bell Labs, and the further research of Bell Labs into operating systems, languages, on-the-fly...
Bada is a South Korean K-pop singer. Her birth name is Choi Sung-hee. Bada studied Korean traditional vocal music at Dankook University. As the former lead vocal from the now defunct S.E.S., Bada has released three solo albums and two singles. Before the release of her third album, Bada started a...
A Linux distribution is a member of the family of Unix-like operating systems built on top of the Linux kernel. Such distributions are operating systems including a large collection of software applications such as word processors, spreadsheets, media players, and database applications...
The Ångström distribution is a Linux distribution for a variety of embedded devices. The distribution is the result of a unification of developers from the OpenZaurus, OpenEmbedded, and OpenSIMpad projects...
BackTrack is an operating system based on the Ubuntu GNU/Linux distribution aimed at digital forensics and penetration testing use. It is named after backtracking, a search algorithm...
Google Chrome OS is a Linux-based operating system designed by Google to work exclusively with web applications. Google announced the operating system on July 7, 2009 and made it an open source project, called Chromium OS, that November....
DSLinux is a port of the Linux operating system to the Nintendo DS. DSLinux was maintained until sometime in 2010.-Software:DSLinux runs a modified μClinux kernel. It is based on uCLinux 2.6.14 . It only runs in textmode and which is displayed using a custom framebuffer console driver...
Debian is a computer operating system composed of software packages released as free and open source software primarily under the GNU General Public License along with other free software licenses. Debian GNU/Linux, which includes the GNU OS tools and Linux kernel, is a popular and influential...
ELinOS is a commercial development environment for embedded Linux. It consists of a Linux distribution for the target embedded system and development tools for a development host computer. The development host computer usually is a standard desktop computer running Linux or Windows...
Fedora is a RPM-based, general purpose collection of software, including an operating system based on the Linux kernel, developed by the community-supported Fedora Project and sponsored by Red Hat...
Gentoo Linux is a computer operating system built on top of the Linux kernel and based on the Portage package management system. It is distributed as free and open source software. Unlike a conventional software distribution, the user compiles the source code locally according to their chosen...
GoboLinux is a free and open source operating system whose most prominent feature is a reorganization of the traditional Linux file system. Rather than following the Filesystem Hierarchy Standard like most Unix-like systems, each program in a GoboLinux system has its own subdirectory tree, where...
iPodLinux is a µClinux-based Linux distribution designed specifically to run on Apple Inc.'s iPod. When the iPodLinux kernel is booted it takes the place of Apple's iPod operating system and automatically loads Podzilla, an alternative GUI and launcher for a number of additional included programs...
Maemo is a software platform developed by the Maemo community for smartphones and Internet tablets. It is based on the Debian Linux distribution, but has no relation to it...
MeeGo is a Linux-based open source mobile operating system project. Primarily targeted at mobile devices and information appliances in the consumer electronics market, MeeGo is designed to act as an operating system for hardware platforms such as netbooks, entry-level desktops, nettops, tablet...
-Business:* Management Expense Ratio* Market Exchange Rate* Merrill Lynch's former NYSE stock symbol* Management with Executive Responsibility -Entertainment:* La mer , an orchestral composition by the French impressionist composer Claude Debussy...
MontaVista Software is a software developer that develops embedded Linux system software, development tools, and related software. Its products are targeted at other corporations developing embedded systems such as automotive electronics, communications equipment, mobile phones, and other...
Slackware is a free and open source Linux-based operating system. It was one of the earliest operating systems to be built on top of the Linux kernel and is the oldest currently being maintained. Slackware was created by Patrick Volkerding of Slackware Linux, Inc. in 1993...
Timesys is a privately owned company that helps software development teams build and maintain a custom Linux platform for a wide variety of embedded processors from semiconductor manufacturers such as Atmel, Freescale, Intel, Texas Instruments, and Xilinx....
Ubuntu is a computer operating system based on the Debian Linux distribution and distributed as free and open source software. It is named after the Southern African philosophy of Ubuntu...
webOS
Wind River Linux
BSD
The following BSD derivatives support ARM processors:
RISC iX was a Unix operating system designed to run on the Acorn Archimedes. Heavily based on 4.3BSD, it was initially completed in 1988 — a year after Arthur but prior to RISC OS.- Features :...
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
NetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...
OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...
iOS is an operating system for iPad, iPhone, iPod Touch, and Apple TV.IOS may also refer to:-Companies and organisations:* Illinois Ornithological Society, American state-based bird club...
Windows
Microsoft announced on 5 January 2011 that the next major version of the Windows NT
Windows NT
Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...
Windows 8 is the codename for the next version of the Microsoft Windows computer operating system following Windows 7. It has many changes from previous versions. In particular it adds support for ARM microprocessors in addition to the previously supported x86 microprocessors from Intel and AMD...
) will include support for ARM processors. Microsoft demonstrated a preliminary version of Windows (version 6.2.7867) running on an ARM-based computer at the 2011 Consumer Electronics Show
Consumer Electronics Show
The International Consumer Electronics Show is a major technology-related trade show held each January in the Las Vegas Convention Center, Las Vegas, Nevada, United States. Not open to the public, the Consumer Electronics Association-sponsored show typically hosts previews of products and new...
. The ARM architecture is also supported by Microsoft's mobile operating systems, Windows Phone
Windows Phone
Windows Phone is a mobile operating system developed by Microsoft, and is the successor to its Windows Mobile platform, although incompatible with it. Unlike its predecessor, it is primarily aimed at the consumer market rather than the enterprise market...
Windows Mobile is a mobile operating system developed by Microsoft that was used in smartphones and Pocket PCs, but by 2011 was rarely supplied on new phones. The last version is "Windows Mobile 6.5.5"; it is superseded by Windows Phone, which does not run Windows Mobile software.Windows Mobile is...
AMULET is a series of microprocessors that implement the ARM processor architecture. Developed by the group under the University of Manchester's computer science school , AMULET is unique from other ARM implementations in being an asynchronous microprocessor, not making use of a square wave clock...
ARM Instruction Set Simulator, ARMulator, is one of the software development tools provided by the development systems business unit of ARM Limited to all users of ARM-based chips. It owes its heritage to the early development of the instruction set by Sophie Wilson...
ARMware is a multi-platform software emulator for ARM-based PDA. It has a built-in dynamic recompiler to translate the ARM machine code to x86 machine code. This recompiler uses SSA form as its intermediate representation. Besides the CPU core emulation, it can also emulate several peripherals,...
, a virtual machine that emulates an ARM-based PDA.
QEMU is a processor emulator that relies on dynamic binary translation to achieve a reasonable speed while being easy to port on new host CPU architectures....
, a virtual machine which supports a lot of ARM processors (armXXXX, cortex-XX, ti925t, pxa2XX, pxa270-XX, any).
LPC2000 is a series of 32-bit microcontrollers from NXP Semiconductors. They are based on a 1.8 V ARM7TDMI-S core operating at up to 80 MHz together with a variety of peripherals including serial interfaces, 10-bit ADC/DAC, timers, capture compare, PWM, USB interface, and external bus options...
SkyEye simulator – an open source ARM Instruction Set Simulator
The Amber processor core is an Open-source ARM-compatible 32-bit RISC processor. It is hosted on the OpenCores website and is part of a movement to develop a library of open source hardware intellectual property. The Amber core is fully compatible with the ARMv2 instruction set and is therefore...
– an open source ARM core developed in Verilog HDL.
Symbian is a mobile operating system and computing platform designed for smartphones and currently maintained by Accenture. The Symbian platform is the successor to Symbian OS and Nokia Series 60; unlike Symbian OS, which needed an additional user interface system, Symbian includes a user...
Microsoft Windows CE is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows...
Windows Phone is a mobile operating system developed by Microsoft, and is the successor to its Windows Mobile platform, although incompatible with it. Unlike its predecessor, it is primarily aimed at the consumer market rather than the enterprise market...
iOS is an operating system for iPad, iPhone, iPod Touch, and Apple TV.IOS may also refer to:-Companies and organisations:* Illinois Ornithological Society, American state-based bird club...
Inferno is a distributed operating system started at Bell Labs, but is now developed and maintained by Vita Nuova Holdings as free software. Inferno was based on the experience gained with Plan 9 from Bell Labs, and the further research of Bell Labs into operating systems, languages, on-the-fly...
A plug computer is a small form factor server for use in the home or office. Compared to their PC-based counterparts, plug computers are lower cost, consume less power, often do not have a video card, and are intended to be powered up at all times...
The Raspberry Pi is a single-board computer developed by the Raspberry Pi Foundation. Scheduled for public release in December 2011, the foundation plans to release two versions that range from US$25 to $35...
, a $25 ARM-based computer
Further reading
The Definitive Guide to the ARM Cortex-M3; 2nd Edition; Joseph Yiu; Newnes; 479 pages; 2009; ISBN 978-1856179638. (Online Sample)
The Definitive Guide to the ARM Cortex-M0; 2nd Edition; Joseph Yiu; Newnes; 552 pages; 2011; ISBN 978-0123854773. (Online Sample)
External links
, ARM Ltd.
The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.
