ARM

ARM, previously Advanced RISC Machine, originally Acorn RISC Machine, is a family of RISC for computer processors, configured for various environments. develops the architecture and licenses it to other companies, who design their own products that implement one of those architectures—including s (SoC) and s (SoM) that incorporate memory, interfaces, radios, etc. It also designs that implement this  and licenses these designs to a number of companies that incorporate those core designs into their own products.

Background
Processors that have a RISC architecture typically require fewer s than those with a (CISC) architecture (such as the x86 processors found in most personal computers), which improves cost, power consumption, and heat dissipation. These characteristics are desirable for light, portable, battery-powered devices—including s, s and s, and other s —but are also useful for s and  to some degree. For s, which consume large amounts of electricity, ARM is also a power-efficient solution.

With over 130 billion ARM processors produced,    As of 2019, ARM is the most widely used  (ISA) and the ISA produced in the largest quantity. Currently, the widely used Cortex s, older "classic" cores, and specialized variants are available for each of these to include or exclude optional capabilities.

Apple and ARM
In the late 1980s, Apple Computer and started working with Acorn on newer versions of the ARM core. In 1990, Acorn spun off the design team into a new company named Advanced RISC Machines Ltd., which became ARM Ltd when its parent company,  plc, was floated on the  and  in 1998. Apple invested 3 million for a 30% stake in the venture. The new Apple-ARM work would eventually evolve into the ARM6, first released in early 1992. Apple used the ARM6-based ARM610 as the basis for their Newton PDA. However, with disappointing sales, Apple closed down the Newton Systems Group in 1998 and sold its stake in ARM for $800 million in desperately needed cash.

In 2001, Apple released the first iPod, which used a ARM-based processor from PortalPlayer and ran an operating system designed by Pixo, which was co-founded and staffed by former Newton employees.

Apple licensed ARM technology for the A4, A5, and A5X and other early processors used in its iPhone and iPad lines. However, Apple acquired P.A. Semi for $278 million in April 2008 to bring in-house to the company. The Apple A6 contained a custom CPU designed internally at Apple (called "Swift") instead of one licensed from ARM.