5.7.3 Binary Translation In previous discussions we have noted that significant adaptation is generally not practical fora program in binary (executable) form. In spite of this, there are times when it becomes essential to convert software already compiled for one architecture into a form that can be used on a very different architecture. Two well-known examples of this approach have arisen as major computer vendors migrated to newer, RISC-class architectures: The change in Digital systems from the VAX to the Alpha The change in Macintosh systems from the 68000 to the PowerPC In these situations a great deal of application software, already in executable form for the older environments, must be made to work in the newer one. To meet this need, strategies have evolved for effective binary translation as a transitional strategy. Typically, this approach uses a combination of translation before execution where possible, and run-time emulation otherwise. The success of the approach may rely on strong assumptions, such as the assumption that the program being translated is a well-behaved client of a particular operating system.
