Problem solved, the "cpu/nb" volt is called "NB core" voltage in bios. I changed it by a little first like 0.025+ and couldnt raise the cpu/nb from 2400 to 2600. And after the + volt on the nb core voltage aida64 and such programs still shows cpu/nb voltage at stock. So i raised the nb core voltage to 0.125+ and raised cpu/nb speed to 2600mhz and logged into windows and it worked, but still in aida64 and such programs the cpu/nb volt shows up as stock.
So the "Nb core" is the cpu/nb in the Gigabyte990fx ud5 rev 3.0 motherboard! And if you have same problem as i had, raise nb core with offset value 0.125+v and try 2600mhz cpu/nb speed. good luck.