Rosetta (software)

Macintosh has used CPUs with several different instruction set architectures (ISA): the Motorola 68000 series, PowerPC, Intel x86, and ARM64 in Apple silicon. Each ISA is incompatible, necessitating a transition plan based on a software layer to emulate the previous ISA on the succeeding one. With the launch of Power Macintosh, the Mac 68K emulator is part of System 7.1.2 and later. This emulator uses PowerPC features and is embedded at the lowest levels of the operating system, integrated with the Mac OS nanokernel. This means that the nanokernel is able to intercept PowerPC interrupts, translate them to 68k interrupts (then doing a mixed mode switch, if necessary), and then execute 68k code to handle the interrupts. This allows 68k and PowerPC code to be interspersed within the same fat binary. ==Rosetta==

Apple launched Rosetta in 2006 upon the Mac transition to Intel processors from PowerPC. It is in Mac OS X Tiger 10.4.4 "Tiger", the version that launched the x86-based Macs, and allows many unmodified PowerPC applications to automatically run on Intel-based Mac computers. Rosetta is based on QuickTransit technology. It has no graphical user interface, and launches transparently, which led Apple to describe Rosetta as "the most amazing software you'll never see". Rosetta is optionally installable in Mac OS X 10.6 "Snow Leopard". Rosetta is neither included nor supported in Mac OS X 10.7 "Lion" (released in 2011) or later. ==Rosetta 2==

In 2020, Apple announced Rosetta 2 would be bundled with macOS Big Sur, to aid in the Mac transition to Apple silicon. The software permits many applications compiled exclusively for execution on x86-64-based processors to be translated for execution on Apple silicon. In addition to the just-in-time (JIT) translation support, Rosetta 2 offers ahead-of-time compilation (AOT), with the x86-64 code fully translated, just once, when an application without a universal binary is installed on an Apple silicon Mac. Rosetta 2's performance has been praised greatly. In some benchmarks, x86-64-only programs performed better under Rosetta 2 on M1 than native x86-64. One of the key reasons why Rosetta 2 provides such a high level of translation efficiency is the support of x86-64 memory ordering in the M1 SoC. The SoC also has dedicated instructions for computing x86 flags. Since macOS Ventura, Linux guest operating system virtual machines can install Rosetta 2 as a guest runtime binary to run x86-64 Linux apps. At WWDC 2025, Apple stated that most Rosetta 2 features will be removed from macOS with version 28 in 2027, with support limited to unmaintained games. ==See also==