DIGITAL FX!32: Combining Emulation and Binary Translation

Vol. 9 No. 1 1997 3 Three factors contribute to the success of a microprocessor: price, performance, and software availability. The DIGITAL FX!32 product addresses the third factor, software availability, by making hundreds of new applications available on Alpha-based platforms running the Windows NT operating system. DIGITAL FX!32 software combines emulation and binary translation to provide fast, transparent execution of Intel x86 applications on Alpha systems. Since its introduction in 1992, the Alpha microprocessor has been the fastest microprocessor available. A large number of native applications are available on Alpha systems, particularly those applications that require a high-performance processor. With the introduction of DIGITAL FX!32 software, 32-bit programs that can be installed and executed on x86 systems running the Windows NT 4.0 operating system can also be installed and executed on Alpha systems running Window NT 4.0. Except for having to specify that a program is an x86 application, installing and running an application is the same on an Alpha system as on an x86 system. The performance of an x86 application running on a high-end Alpha system is similar to the performance of the same application running on a high-end x86 system. A number of systems have successfully used emulators to run applications on platforms for which the applications were not initially targeted. The major drawback has been poor performance. Several emulators have used dynamic translation, translating small segments of a program as it is executed, to achieve better performance than that obtained by an interpreter alone. Dynamic translation involves a basic trade-off between the amount of time spent translating and the resulting benefit of the translation. If an emulator spends too much time on the translation and related processing, the executing program will be unresponsive. This limits the optimizations that can be performed by the emulator using dynamic translation. FX!32 overcomes the performance problem by not doing any translation while the application is executing. Rather, FX!32 captures an execution profile that is later used by a binary translator to translate into native Alpha code those parts of the application that have been executed. Since the translator runs in the backDIGITAL FX!32: Combining Emulation and Binary Translation Raymond J. Hookway Mark A. Herdeg