Anything Intel beyond a 486DX has a FPU built in. So the difference is not the floating point. I'm not up on CPU's like I used to be but I don't think any common processors (outside of embedded) use software floating point anymore.
The last I know of was was the 486SX which is circa 1993~4.
Hm... Now you made me cannot go sleep ;-) No, not that serious, but it is better to find a answer. Would you please post your answer, if you find one later? and I will do the same thing, if I suddenly realize anything.