Can anybody answer me how much kh/s i should have with intel core i7 4930?
I use minerd_w64_sse4 on windows 8.1 and get only 48kh/s per threat means only ~600kh/s for 12/12 threats, i feel it's a bit low.
I think you should be getting a lot higher than that - I've got an i7 2600K and I get over 800kh/s for 8/8 threads (-a quark), and your processor is a lot newer than mine.
It might be worth giving the miners here a go:
https://bitcointalk.org/index.php?topic=353448.0