Hey guys

I'm pretty new to this so i even don't know if i'm in the right section for this question but...

i want to know how I can find or calculate the generation speed of a CPU or a GPU... just to know what for a bad idea brute force may be...
so i want to know how much passwords my cpu and gpu can generate per period of time or how long it will take to generate a rainbowtable for example...
also how I can use my whole idle cpu speed and gpu (if thats even possible on a normal pc...) for for example cain or hydra...

thnx in advance