But ten years later in 2013, SSE had been standard in all x86 CPUs for a while - the OS depended on it being there, so you could rely on it. So of course by default the compilers use it - in fact you have to go out of your way to make them emit the old (slightly slower) x87 code. SSE uses a much more well-defined precision of either 32 or 64 bit according to what the code asks for - it's much more predictable.