[A 64-bit KSP might be closer than we think(or at least Squad is working on it)]

When 32-bit processes run, they use some level of emulation that slows things down a bit.

x64 is a superset of the x86 instruction set, so I doubt there is any emulation going on.

[[WIP][1.8.1, 1.9.1, 1.10.1, 1.11.0–2, 1.12.2–5] Principia—version ‎Καραθεοδωρή, released 2024-04-08—n-Body and Extended Body Gravitation]

Speed will be further increased by rewriting the numerical integration in (unmanaged) C++, interfaced with C# through C++/CLI. The unmanaged C++ (compiled with clang) will use 80-bit extended precision 'long double' (64-bit mantissa instead of 53-bit) for added precision.

If speed is the aim, SSE extensions could be a faster alternative to x87 floating point but would require sacrificing extended precision.