Since Apple's 2005–2006 transition to Intel processors, all Macintosh computers, until the transition to Apple silicon, have used Intel's x86 CPU architecture. Main article: Mac transition to Intel processors Apple held a 43% stake in the company, which was reduced to 14.8% in 1999. The company was named Advanced RISC Machines Ltd, becoming the new meaning of the ARM acronym.

In 1990, a new joint-venture was created between Acorn, Apple and VLSI Technology with the goal of pursuing the development of the ARM processor. The project was cancelled but Apple again partnered with Acorn when it needed a low-power, efficient processor for its future Newton PDA. In 1985, Apple's Advanced Technology Group worked with Acorn to create an experimental prototype, code-named Mobius, to replace the Apple II, using a modified ARM processor. In 1983, Acorn Computers started working on a project to design its own CPU architecture and instructions set, called the Acorn RISC Machine (ARM). Intel CTO Mike Mayberry countered that quality assurance problems may arise at large scale from any CPU vendor. In June 2020, former Intel principal engineer François Piednoël said Intel's 'abnormally bad' quality assurance in its Skylake processors, making Apple 'the number one filer of problems in the architecture', helped Apple decide to migrate. In 2019, Apple blamed Intel processor shortages for a decline in Mac sales. Meanwhile, a 2018 report suggested that Intel chip issues prompted a redesign of the MacBook. Apple reportedly had trouble with Intel modems for iPhones in 2017 due to technical issues and missed deadlines. In the 2010s, media reports documented Apple's frustrations and challenges with the pace and quality of Intel's technology development. Between October 2016 and August 2020, Intel-based Macs with Apple-designed ARM co-processors were released.

Apple has designed its own custom ARM chips since 2009, which it has officially deployed since 2010 in its iPhone, iPad, iPod, Apple TV and Apple Watch product lines, as well as AirPods, Beats and HomePod. Apple first used the ARM architecture in 1993 in its Newton personal digital assistant, followed by the iPod in 2001 and the iPhone in 2007. Since 2006, Apple has used Intel processors in Macintosh computers. A first-generation MacBook Pro from 2006, one of the first line of Mac computers to feature an Intel processor instead of a PowerPC processor.

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