Rosetta is the name given to the mysterious new PowerPC-to-Intel emulation layer Apple is employing, and which has been recently confirmed to be a variant of QuickTransit.


Rosetta is a translation process that runs a PowerPC binary on an Macintosh using an Intel microprocessor—it allows applications to run as nonnative binaries. Many, but not all, applications can run translated. Applications that run translated will never run as fast as they run as a native binary because the translation process itself incurs a processing cost. How compatible your application is with Rosetta depends on the type of application it is. Applications that have a lot of user interaction and low computational needs, such as a word processor, are quite compatible. Those that have a moderate amount of user interaction and some high computational needs or that use OpenGL are, in most cases, also quite compatible. Those that have intense computing needs aren’t compatible. This includes applications that need to repeatedly compute fast Fourier transforms (FFTs), that compute complex models for 3-D modelling, or compute ray tracing. To the user, Rosetta is transparent.

Unlike Classic, when the user launches an application, there aren’t any visual cues to indicate that the application is translated. The user may perceive that the application is slow to start up or that the performance is slower than it is on a Macintosh using a PowerPC microprocessor. The user can discover whether an application has only a PowerPC binary by looking at the Finder information for the application. (See “Determining Whether a Binary is Universal” (page 18).) The purpose of this appendix is to discuss the sorts of applications that can run translated, describe how Rosetta works, point out special considerations for translated applications, and provide troubleshooting information if your application won’t run translated but you think that it should.