Mono's main developers use x86 systems and its the most tuned version, currently it supports:
Linux. Windows. BSD (Requires a modern version for proper thread support). Solaris/x86
Mono on x86 supports both Just-in-Time (JIT) compilation as well as Ahead-of-Time (AOT) compilation, the later produces Position Independent Code.
X86 Specific Optimizations
Thread local storage (TLS): on systems that support TLS, Mono is able to take advantage of it. x86 peephole optimizations. Instruction selector is able to pick best instructions on x86.
