Rosetta 2

Rosetta 2, part of Project Kalamata, is an initiative within Apple Inc. to facilitate the transition of the Mac product line from Intel processors to its own processors through the use of emulation.

History
Apple had previously announced that it would switch from PowerPC processors to Intel processors in 2005 when IBM's development of the PowerPC G5 could no longer keep up with its product road map. An earlier version of Rosetta was a key component of the transition by allowing PowerPC software to run in emulation on Intel processors.

In April 2008, Apple acquired P.A. Semi for $278 million to bring fabless processor design in-house to the company, and to reduce its dependence on Samsung for central processing units in its mobile products, and later Intel for its desktop products.

Development and announcement
Apple initiated Project Kalamata in 2018 with the goal of developing a 5nm version of the Apple A14 to replace Intel processors by 2021, starting with entry level Macs. This was realized in November 2020 with the introduction of new MacBook Air, MacBook Pro, and Mac mini models based on the Apple M1 processor.

Craig Federighi announced Rosetta 2 at 2020 Worldwide Developers Conference on June 22. It allows emulation of Intel processors on systems built with Apple processors, such as the 2020 Developer Transition Kit, which uses an Apple A12Z processor. The performance hit from Rosetta 2 was reportedly around 20%, allowing the newer M1 processor to run Intel software in emulation faster than Apple's Intel-based models. However, some users expressed concern that the swap files being generated by the translation of non-native code were wearing out the life expectancy of the affected models' solid-state drives.

Issues
Rosetta 2 allows Apple processors to run Intel code through dynamic recompilation. However, some users expressed concern that the swap files being generated by the translation of non-native code were wearing out the life expectancy of the Macs' solid-state drives, especially in base models configured with less RAM. This issue was addressed by Apple in the macOS 11.4 update.

Articles

 * Apple could beat Intel to 5nm as Project Kalamata CPU resurfaces by Carly Page at TechRadar (2020-04-23)
 * Intel officials believe that ARM Macs could come as soon as 2020 by Mike Wuerthele at AppleInsider (2019-02-21)
 * How Apple Built a Chip Powerhouse to Threaten Qualcomm and Intel by Mark Gurman at Bloomberg Technology (2018-01-29, archived 2018-01-29)