Compatibility layer

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In software engineering, a compatibility layer is an interface that allows binaries for a legacy or foreign system to run on a host system. This translates system calls for the foreign system into native system calls for the host system. With some libraries for the foreign system, this will often be sufficient to run foreign binaries on the host system. A hardware compatibility layer consists of tools that allow hardware emulation.

Software[edit]

Examples include:


A compatibility layer avoids both the complexity and the speed penalty of full hardware emulation. Some programs may even run faster than the original, e.g. some Linux applications running on FreeBSD's Linux compatibility layer may or may not perform better than the same applications on Red Hat Linux, and benchmarks are occasionally run on Wine to compare it to Windows NT-based operating systems.[6]

Even on similar systems, the details of implementing a compatibility layer can be quite intricate and troublesome; a good example is the IRIX binary compatibility layer in the MIPS architecture version of NetBSD.[7]

A compatibility layer requires the host system's CPU to be (upwardly) compatible to that of the foreign system. Thus, for example, an MS Windows compatibility layer is not possible on PowerPC hardware, since MS Windows requires an x86 CPU; in that case, full emulation is needed.

Hardware[edit]

Hardware compatibility layers involve tools that allow hardware emulation. Some hardware compatibility layers involve breakout boxes, since breakout boxes can provide compatibility for certain computer buses that are otherwise incompatible with the machine.

See also[edit]

References[edit]

  1. ^ Charlie Russel, Microsoft MVP for Windows Server and Tablet PC (2002-02-18). "Application Compatibility in Windows XP". 
  2. ^ "Linux emulation in FreeBSD". 
  3. ^ "Emulation". freebsd.org. Retrieved 2014-03-16. 
  4. ^ "A look inside...". freebsd.org. Retrieved 2014-03-16. 
  5. ^ "NetBSD Binary Emulation". netbsd.org. Retrieved 2014-03-16. 
  6. ^ BenchMark-0.9.5 - The Official Wine Wiki
  7. ^ Emmanuel Dreyfus (August 8, 2002). "IRIX Binary Compatibility, Part 1". onlamp.com. Retrieved 2014-03-16. 

External links[edit]