The
StrongARM is a family of
microprocessorA microprocessor incorporates most or all of the functions of a central processing unit on a single integrated circuit . The first microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal arithmetic on 4-bit words...
s that implemented the
ARM V4The ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Limited. It was known as the Advanced RISC Machine, and before that as the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in terms of numbers produced...
instruction set architecture (ISA). It was developed by
Digital Equipment CorporationDigital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC...
(DEC) and later sold to Intel, who continued to manufacture it before replacing it with the
XScaleThe XScale, a microprocessor core, is Marvell's implementation of the fifth generation of the ARM 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.The XScale architecture is based on the ARMv5TE...
.
History
The StrongARM was a collaborative project between DEC and
ARMARM Holdings is a technology company headquartered in Cambridge, England, UK. The company is best known for its processors, although it also designs, licenses and sells software development tools under the RealView and KEIL brands, systems and platforms, system-on-a-chip infrastructure and software...
to create a faster microprocessor based on (but not totally compatible with) the existing ARM line. The StrongARM was designed to address the upper-end of the low-power embedded market, where users needed more performance than the ARM could deliver while being able to accept more external support. Targets were devices such as newer
personal digital assistantA personal digital assistant is a handheld computer, also known as a palmtop computer. Newer PDAs commonly have color screens and audio capabilities, enabling them to be used as mobile phones , web browsers, or portable media players. Many PDAs can access the Internet, intranets or extranets...
s and
set-top boxA set-top box or set-top unit is a device that connects to a television and an external source of signal, turning the signal into content which is then displayed on the television screen.- History :...
es.
Traditionally, the
semiconductorA semiconductor is a material that has an electrical resistivity between that of a conductor and an insulator, that is, generally in the range 10
3 Siemens/cm to 10
−8 S/cm. Devices made from semiconductor materials are the foundation of modern electronics, including radio,...
division of DEC was located in
MassachusettsThe Commonwealth of Massachusetts is a state in the New England region of the northeastern United States. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. Most of its population of...
. In order to gain access to the design talent in
Silicon ValleySilicon Valley is the southern part of the San Francisco Bay Area in Northern California, United States. The term originally referred to the region's large number of silicon chip innovators and manufacturers, but eventually came to refer to all the high-tech businesses in the area; it is now...
, DEC opened a design center in Palo Alto,
CaliforniaCalifornia is the most populous state in the United States, and the third largest by area. California is the second most populous sub-national entity in the Americas, behind only São Paulo, Brazil...
. This design center was led by Dan Dobberpuhl and was the main design site for the StrongARM project. Another design site which worked on the project was in
Austin, TexasAustin is the capital of the U.S. state of Texas and the seat of Travis County. Located in Central Texas on the eastern edge of the American Southwest, it is the fourth-largest city in Texas and the 15th-largest in the United States. It was the third-fastest-growing large city in the nation...
that was created by some ex-DEC designers returning from
Apple ComputerApple Inc. is an American multinational corporation that designs and manufactures consumer electronics and computer software products. The company's best-known hardware products include Macintosh computers, the iPod and the iPhone...
and
MotorolaMotorola, Inc. is an American, multinational, Fortune 100, telecommunications company based in Schaumburg, Illinois. It is a manufacturer of wireless telephone handsets, and also designs and sells wireless network infrastructure equipment such as cellular transmission base stations and signal...
. The project was set up in 1995, and quickly delivered their first design, the
SA-110.
This was immediately incorporated into newer versions of the
Apple NewtonThe MessagePad was the first series of personal digital assistant devices developed by Apple Computer 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
AcornAcorn Computers 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...
Risc PCThe Risc PC was Acorn Computers's next generation RISC OS/Acorn RISC Machine computer, launched in 1994, which superseded the Acorn Archimedes....
,
EidosEidos Interactive Ltd. was a video game developer and publisher based in England. It is now part of Square Enix Europe.Its best-known game series include Tomb Raider, Hitman, Commandos, Deus Ex, Legacy of Kain, Thief, Timesplitters, and Fear Effect...
Optima video editing system, as well as a number of other products.
StrongARM was sold to Intel as part of a lawsuit settlement in 1997. Intel used the StrongARM to replace their ailing line of RISC processors, the
i860The Intel i860 was a RISC microprocessor from Intel, first released in 1989. The i860 was one of Intel's first attempts at an entirely new, high-end instruction set since the failed Intel i432 from the 1980s. It was released with considerable fanfare, and obscured the subsequent release of the...
and
i960Intel'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...
.
A new StrongARM core, the SA-2 was developed by Intel. It was introduced in 2000 as the
XScaleThe XScale, a microprocessor core, is Marvell's implementation of the fifth generation of the ARM 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.The XScale architecture is based on the ARMv5TE...
.
When the semiconductor division of DEC was sold off to Intel, the Palo Alto design group spun off to become SiByte, a
start-upStartup or start-up may refer to:* Booting, an initialization period that computers and electronics go through when first turned on;* Commissioning, the act of starting for the first time a technical installation;...
company building
MIPS architectureMIPS is a reduced instruction set computing instruction set architecture developed by MIPS Computer Systems . The early MIPS architectures were 32-bit, and later versions were 64-bit...
SOCSOC or SoC may refer to:Science and technology* Security Operation Center * Self-organized criticality, a property of dynamical systems in physics* Separation of concerns, a program design principle in computer science...
s for the networking market. The Austin design group spun off to become Alchemy Semiconductor, another start-up company building MIPS SOCs for the hand-held market.
Description
The StrongARM family are faster versions of the existing ARM processors with a somewhat different
instruction setAn instruction set is a list of all the instructions, and all their variations, that a processor can execute.Instructions include:* Arithmetic such as add and subtract...
. Clocked at 206MHz they can perform up to 235 MIPS (1.14 MIPS/MHz). They have limited software compatibility with the earlier ARM families due to their separate caches for data and instructions, which causes
self-modifying codeIn computer science, self-modifying code is code that alters its own instructions while it is executing - usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code thus simplify maintenance...
to fail. These features were later included in some ARMv4 architectures (notably, the ARM/Texas Instruments ARM925). The StrongARM has an "invalidate cache line" instruction to let the CPU know to reload from main memory. This situation arises rarely in typical software however, and StrongARM is not the only processor to have made such a sacrifice. The
MotorolaMotorola, Inc. is an American, multinational, Fortune 100, telecommunications company based in Schaumburg, Illinois. It is a manufacturer of wireless telephone handsets, and also designs and sells wireless network infrastructure equipment such as cellular transmission base stations and signal...
68020The 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.- Description :...
, for instance, caused similar compatibility problems for any software designed for the earlier
68000The Motorola 68000 is a 16/32-bit
CISC microprocessor core designed and marketed by Freescale Semiconductor...
and
68010The Motorola MC68010 processor is a 16/32-bit microprocessor from Motorola, released in 1982. In common with the Motorola 68000 naming convention, it is usually just referred to as the 010 ....
models.
SA-110
The SA-110 was the first microprocessor in the StrongARM family. It was introduced in early 1996, debuting at 200 MHz. In October 1996, a 233 MHz version was introduced. Throughout 1996, the SA-110 was the highest performing microprocessor for portable devices. The SA-110 was available in 100, 160, 166, 200, 233 MHz versions. The SA-110's first design win was the Apple MessagePad 2000. The SA-110's lead designers were Daniel W. Dobberpuhl, Gregory W. Hoeppner, Liam Madden, and Richard T. Witek.
Description
The SA-110 had a simple microarchitecture. It was scalar, in-order design with a five-stage
classic RISC pipelineIn the history of computer hardware, some early reduced instruction set computer central processing units used a very similar architectural solution, now called a classic RISC pipeline. Those CPUs were: MIPS, SPARC, Motorola 88000, and later DLX....
. The microprocessor was partitioned into several blocks, the IBOX, EBOX, IMMU, DMMU, BIU, WB and PLL. The IBOX contained hardware that operated in the first two stages of the pipeline such as the program counter. It fetched, decoded and issued instructions. It also handled branch instructions. The SA-110 did not have branch prediction hardware, but had mechanisms for their speedy processing. Complex ARM instructions were translated by the IBOX into sequences of simpler instructions by during the second stage.
Instructions are executed in the third stage by hardware in the EBOX. The EBOX contained the
register fileA 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...
,
arithmetic logic unitIn computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
(ALU),
barrel shifterA 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...
,
multiplierThe term multiplier may refer to:In electrical engineering:* Binary multiplier, a digital circuit to perform rapid multiplication of two numbers in binary representation...
and condition code logic. The register file had three read ports and two write ports. The ALU and barrel shifter executed instructions in a single cycle. The multiplier had a latency of multiple cycles.
The IMMU and DMMU are memory management units for instructions and data, respectively. Each MMU contained a 32-entry fully-associative TLB that can map 4 KB, 64 KB or 1 MB pages. The write buffer (WB) has eight 16-byte entries. It enables the pipelining of stores. The bus interface unit (BIU) provided the SA-110 with an external interface.
The PLL generates the internal clock from a 3.68 MHz input clock. It was not designed by DEC, but was contracted to the Centre Suisse d'Electronique et de Microtechnique (CSEM) located in Neuchâtel, Switzerland.
The Icache and Dcache each have a capacity of 16 KB and are 32-way set associative and virtually addressed. The SA-110 was designed with slow (and therefore low cost) memory in mind and therefore the high set associativity allows a higher hit rate than competing designs, and the use of virtual addresses allows memory to be simultaneously cached and uncached. The caches take up half the die area.
The SA-110 contained 2.5 million transistors and measured 7.8 mm by 6.4 mm for an area of 49.92 mm
2. It was fabricated by DEC in their CMOS-6 process, their sixth-generation complementary metal–oxide–semiconductor (CMOS) process with some modifications. CMOS-6 has a 0.35 µm feature size, a 0.25 µm effective channel length but for use with the SA-110, only three levels of aluminium interconnect. It used a power supply with a variable voltage of 1.2 to 2.2 V to enable designs to find a balance between power consumption and performance (higher voltages enable higher clock rates).
SA-1100
The SA-1100 was a derivative of the SA-110 developed by DEC initially targeted for
PDA-Science and technology :* Personal digital assistant, an electronic device which can include some of the functions of a computer, a cellphone, a music player, and a camera* Patent ductus arteriosus, a heart defect* photodiode array, a type of detector...
s. It has an integrated color LCD controller. The SA-1100 had a companion chip, the SA-1101. The companion chip provided additional peripherals to complement those integrated on the SA-1100 such as a video output port, two
PS/2 ports, a USB controller and a PCMCIA controller that replaces that on the SA-1100. It was developed by DEC, but was only partially complete when StrongARM was acquired by Intel, who had to finish the design. It was fabricated at DEC's former
Hudson, MassachusettsHudson is a town in Middlesex County, Massachusetts, United States. The population was 18,113 at the 2000 census, and estimated to have reached about 19,580 in 2007...
fabrication plant, which was also sold to Intel.
It contained 2.5 million transistors and measured 8.24 mm by 9.12 mm (75.15 mm
2). It was fabricated in a 0.35 µm CMOS process with three levels of aluminium interconnect and was packaged in a 208-lead
thin quad flat packThin Quad Flat Pack is a type of SMD package. Components of this type provide the same benefit of the metric QFP package, but are thinner and have a standard lead-frame footprint ....
(TQFP).
SA-1110
The SA-1110 was a derivative of the SA-110 developed by Intel introduced in 1999. It operated at 133 or 206 MHz and added an on-die
memory controllerThe memory controller is a digital circuit which manages the flow of data going to and from the main memory. It can be a separate chip or integrated into another chip, such as on the die of a microprocessor....
that supports 66 (133 MHz version only) or 103 MHz (203 MHz version only)
SDRAMSynchronous dynamic random access memory is dynamic random access memory that has a synchronous interface. Traditionally, dynamic random access memory has an asynchronous interface which means that it responds as quickly as possible to changes in control inputs...
. It was used in mobile phones, personal data assistants (PDAs) such as the Compaq (later HP)
iPAQiPAQ presently refers to a Pocket PC and personal digital assistant first unveiled by Compaq in April 2000; the name was borrowed from Compaq's earlier iPAQ Desktop Personal Computers. Since Hewlett-Packard's acquisition of Compaq, the product has been marketed by HP...
and HP Jornada, and the
SimputerThe Simputer is a self-contained, open hardware handheld computer, designed for use in environments where computing devices such as personal computers are deemed inappropriate...
.
SA-1500
The SA-1500 was a derivative of the SA-110 developed by DEC initially targeted for set top boxes. It was designed and manufactured in low volumes by DEC but was never put into production by Intel. The SA-1500 operated at 200 to 300 MHz. New features include a floating-point unit and
SIMDIn computing, SIMD is a technique employed to achieve data level parallelism.- History :...
instructions. A companion chip provided additional video and audio processing capabilities.
It contains 3.3 million transistors and measures 60 mm
2. It was fabricated in a 0.28 µm CMOS process. It used a 1.5 to 2.0 V internal power supply and 3.3 V I/O, consuming less than 0.5 W at 100 MHz and 2.5 W at 300 MHz. It was packaged in a 240-pin
metric quad flat packageA QFP or Quad Flat Package is an integrated circuit package with leads extending from each of the four sides. It is used primarily for surface mounting ; socketing is rare, and hole mounting is not possible. There are versions having from 32 to over 200 pins with a pitch ranging from 0.4 to 1.0 mm...
(MQFP) or a 256-ball ball grid array.
Further reading
- Halfhill, Tom R. (19 April 1999). "Intel Flexes StrongARM With New Chips". Microprocessor Report.
- Santhanam, S. et al. (1998). "A low-cost, 300-MHz, RISC CPU with attached media processor". IEEE Journal of Solid-State Circuits, Volume 33, Issue 11.
- Turley, Jim (13 November 1995). "StrongArm Punches Up ARM Performance". Microprocessor Report.
- Turley, Jim (15 September 1997). "SA-1100 Puts PDA on a Chip". Microprocessor Report.
- Witek, Rich; Montanaro, James (1996). "StrongARM: A high-performance ARM processor". Proceedings of COMPCON '96, pp. 188–191.