For intense number-crunching i\'m considering using fixed point instead of floating point. Of course it\'ll matter how many bytes the fixed point type is in size, on what CPU i
Since you are using a general-purpose CPU, I would suggest not using fixed point, unless performance is so critical for your application that you have to count every tic. The hassle of implementing fixed point, and dealing with issues like overflow is just not worth it, when you have a CPU, which will do it for you.
IMHO, fixed point is only necessary when you are using a DSP without hardware support for floating point operations.