Rosetta (software)


Rosetta is a dynamic binary translator developed by Apple Inc. for macOS.
Apple released the first version of Rosetta in 2006 when it changed the instruction set architecture of the Macintosh platform from the PowerPC to the Intel processor. It was initially included with Mac OS X v10.4.4 "Tiger", the version that was released with the first Intel-based Macs, and allowed many PowerPC applications to run on certain Intel-based Mac computers without modification. The name "Rosetta" is a reference to the Rosetta Stone, the discovery that made it possible to comprehend and translate Egyptian hieroglyphs. Rosetta is based on QuickTransit technology. It has no graphical user interface, which led Apple to describe Rosetta as "the most amazing software you'll never see."
Rosetta is not installed by default in Mac OS X v10.6 "Snow Leopard", but can be retained as an option via the installer or Apple Software Update for users who need to run PowerPC applications. Rosetta is neither included nor supported in Mac OS X v10.7 "Lion" or later. Therefore, with Lion and later releases, the Intel Macintosh platform does not support PowerPC applications.
Rosetta 2 is included as of macOS Big Sur to aid in Apple's transition to ARM processors from Intel processors.

Rosetta

Rosetta is part of Mac OS X for Intel operating systems prior to Lion. It translates G3, G4, and AltiVec instructions; however, it does not translate G5 instructions. Therefore, applications that rely on G5-specific instruction sets must be modified by their developers to work on Rosetta-supported Intel-based Macs. According to Apple, applications with heavy user interaction but low computational needs are well suited to translation via Rosetta, while applications with high computational needs are not.
Pre-existing PowerPC versions of Apple "Pro" media-production applications are not supported by Rosetta and require a "crossgrade" to a universal binary version to work on Rosetta-supported Intel-based Macs.
Rosetta does not support the following:
The reason for Rosetta's reduced compatibility compared to Apple's earlier 68k emulator for PPCs lies within its implementation. Rosetta is a user-level program and can only intercept and emulate user-level code. By contrast, the 68k emulator accesses the very lowest levels of the OS by being at the same level as, and tightly connected to, the Mac OS nanokernel on PPC Macs, which means that the nanokernel is able to intercept PowerPC interrupts, translate them to 68k interrupts, and then execute 68k code to handle the interrupts. This allows lines of 68k and PPC code to be interspersed within the same fat binary.

Rosetta 2

Rosetta 2 is included as of macOS Big Sur to aid in Apple's transition to ARM processors from Intel processors. In addition to the just-in-time translation support available in Rosetta, Rosetta 2 includes support for translating an application at installation time.