How is sudden doom normalized/other sd qs?

I cannot get proculus to work as of 4.3 and want to know how this mechanic works.

A-Is it normalized solely to weapon speed to generate a pph based on a desired ppm,
this means-3.6 weapon speed=16.7 attacks per mintute(non modified by haste) and will always normalize to x procs per minute lets arbitrarily say 5 ppm so pph=.29, and therefore can with my actual aspd of 2.93 get 5.93 ppm?
B-Is it instead normalized to your actually aspd?
C-Is there a internal cooldown?
D-What is the ppm or pph per rank/ is it a static amount per rank or does it not increase in the same increment per rank?

Thank you for responses but please do not respond if not actually answering this question. Please no " Rage is better just put points in that" sorta response.