This is the case for example with the x86 .NET jit. The problem is usually when values are moved to 64bit locations rather than keeping them in 80bit fpu registers. This was a huge headache our regression tests for a .NET engineering/FEM application. .NET has no option to force "strict" FPU mode so there is no way of getting reproducible results. What saved us was that the x64 JIT uses only 64 bit, which makes it deterministic.