@Strunkenbold Yes, they can be detected by software, but the information is restricted to "math coprocessor present/yes".
In resume, they can't work separately from main cpu, but once installed it can give more than 32x faster process abitity to calculate decimal numbers.
As a matter of fact, when you run superpi using a fpu processor it is this cpu himself that do all the calculation work, not the main cpu.
It works at the same frequency that main cpu works, no matter if they are sharing the same crystal oscillator or using it's own crystal, it will only work at same main cpu speed.