I have a problem with the new BIOS 1603 and the speed of my 4790. Since the update, the CPU has a fixed multiplier on 38 @ FSB 100MHz. But the default multiplier by the CPU is 36 and the boost multiplier 40. If the system did nothing the multiplier was set down to 8 in older BIOS versions but yet it is fixed @ 38. In the BIOS is all set to "Auto" for the CPU. For a test I have edit all core ratio values to there standards like core ratio min to 8 and core ratio max to 40, but the multiplier is always fixed on 38. I think the BIOS is incompatible with my CPU or I do something wrong.
There have been several reports of that sort of problem with BIOS v1603. Most have been cleared up by reverting to BIOS 1505. Since you are using a 4790K Devil's Canyon, be careful not to revert back too far. IIRC 1505 is the first version compatible with 4790K.