We don't have any reports of issues regarding the maintenance mode for the DX79SI. Our recommendation is checking the warranty options since it seems that the BIOS on your system could be corrupted at some point.
I was wrong because my version of BIOS was 0537 and here is no way to enter to Configuration mode. But after I updated to 0553 it was okay and configuration mode working fine. But still I can't make my processor to reduce its speed when in idle. I tried many option in BIOS and no success. Can you tell me please what wold I do in BIOS to make my I7-3930K reduce speed in idle?