FS-UAE Amiga Emulator


JIT Compiler

FS-UAE includes a Just-in-Time (JIT) compiler for x86 and x86-64. The JIT compiler is used to speed up emulation dramatically, at the expense of some compatibility. The JIT compiler can only be used with 68020 or higher emulated CPUs, and is not compatible with MMU emulation.

Enabling the JIT Compiler

To enable the JIT compiler, use the following option:

jit_compiler = 1

Note: In previous versions of FS-UAE, you would enable the JIT compiler with the option uae_cachesize = 8192. This is no longer sufficient to enable the JIT compiler, and you also do not need to specify cache size any more.

Toggling JIT on/off

It is possible to toggle the JIT compiler on/off during emulation. One use case for this is to speed up your Workbench experience, but disable the JIT before running games, for better compatibility.

TODO: Write how

Note: Enabling JIT during emulation will not work unless FS-UAE was started with the JIT compiler initially on. This is because some FS-UAE initialization is only performed when JIT is enabled.


TODO: Links to option reference:

  • jit_compiler
  • jit_mempory

Additional low-level options:

  • uae_cachesize
  • uae_comp_trustbyte
  • uae_comp_trustword
  • uae_comp_trustnaddr
  • uae_comp_trustlong
  • uae_compfpu