According to ABBREVIATIONFINDER.ORG, ARM is an architecture RISC (Reduced Instruction Set Computer = Computer with reduced instruction set) of 32 bits developed by ARM Holdings. It was called Advanced RISC Machine, and previously Acorn RISC Machine. The ARM architecture is the most widely used 32-bit instruction set in produced units. Originally conceived by Acorn Computers for use in personal computers, the first ARM-based products were the Acorn Archimedes, released in 1987.
The relative simplicity of ARM processors makes them ideal for low-power applications. As a result, they have become dominant in the market for mobile and embedded electronics, embodied in small, low-power, and relatively low-cost microprocessors and microcontrollers. In 2005, about 98% of the more than 1 billion cell phones sold each year used at least one ARM processor. As of 2009, ARM processors are about 90% of all integrated 32-bit RISC processors.
History
The design of ARM began in 1983, as a development project in the company Acorn Computers Ltd. Roger Wilson and Steve Furber, were the pioneers in the development of the technology and in April 1985 they presented their first chip called ARM1, but the ARM2 It was the first to go out into the world and its main characteristic is that it contained a 32-bit data bus.
The ARM2 was a very simple 32-bit microprocessor with only 30,000 transistors, for example the Motorola 68,000 (used by Apple on the Lisa computer) had 70,000 transistors and was 6 years older. The ARM2 also did not have a cache, being this simplicity what allowed a lower use of energy.
In 1991 after several years of work between Apple and Acorn they presented a new model of the ARM core called ARM6 with 35,000 transistors, using it mainly for Apple’s first PDA, the Apple Newton.
It was from the development of the ARM8 that it began to be used within calculators, GPS and mobile devices. We currently find that most devices use the Cortex family of ARM.
The ARM design today has become one of the most used around the world and is present in hard drives, toys, mobiles and tablets. Today, about 75% of 32-bit processors have this chip at their core.
Supported Operating Systems
Android, iOS, WebOS, Linux Kernel and Solaris, are some examples of the operating systems that use this development to support their operating systems.
For example, Apple at the time bought an ARM license, then acquired the PA Semi company, and ultimately ended up designing the A4 processor found inside the iPad and iPhone 4.
2 years ago Microsoft also bought a license to use ARM and is currently developing its operating system with ARM support, this means that those of Redmon have worked hard so that Windows is able to work on low-power processors. Which theoretically will allow us to run Windows 8 on a Smartphone.
The truth is that HTC is developing a new line of Tablets with Windows 8 and ARM’s RISC platform.
Licensing
One of the peculiarities of the company that created ARM, the aforementioned ARM Holdings, is that it does not intend to manufacture its own chips. Instead they license their creations to other manufacturers and this helps to spread their market presence, as well as the revenue provided. Well-known names such as Tegra from Nvidia, OMAP from Texas Instruments or Snapdragon from Qualcomm, are based on ARM technology and are very common in the most famous mobile devices in the sector.
Technologies
Thumb
Newer processors come with an additional instruction set called Thumb, 16 bits (2 bytes) long per instruction, instead of 32 bits (4 bytes) like the standard ARM set. Thumb is a subset of the most frequently used instructions. Being half the length, it is possible to reduce the amount of code and improve its density. The performance can be higher than a 32-bit code where the memory port or communication bus width is less than 32 bits. Typically, applications insert a small range of memory addresses with a 32-bit datapath (for example: Game Boy Advance), and the rest are 16-bit in wide or narrower mode.
The first processor with Thumb technology was the ARM7TDMI. The entire post-ARM9 family, including the Intel XScale processor, have the technology built into their core.
Jazelle
ARM has a technology in place that allows certain types of architectures to execute Java bytecode natively on the hardware. The first processor to use Jazelle was the ARM926EJ-S, with a J to all processors that support this technology.
