ARM

ARM, previously Advanced RISC Machine, originally Acorn RISC Machine, is a family of RISC architectures for computer processors, configured for various environments. Arm Holdings develops the architecture and licenses it to other companies, who design their own products that implement one of those architectures—including systems-on-chips (SoC) and systems-on-modules (SoM) that incorporate memory, interfaces, radios, etc. It also designs cores that implement this instruction set 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 transistors than those with a complex instruction set computing (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 smartphones, laptops and tablet computers, and other embedded systems —but are also useful for servers and desktops to some degree. For supercomputers, 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 instruction set architecture (ISA) and the ISA produced in the largest quantity. Currently, the widely used Cortex cores, older "classic" cores, and specialized SecurCore cores variants are available for each of these to include or exclude optional capabilities.

Apple and ARM
In the late 1980s, Apple Computer and VLSI Technology 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, Arm Holdings plc, was floated on the London Stock Exchange and NASDAQ in 1998. 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.

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 fabless processor design in-house to the company. The Apple A6 contained a custom CPU designed internally at Apple (called "Swift") instead of one licensed from ARM.