I recently upgraded from MSI mobo and 2500K to Maximus VI Gene + 4670K.
I'm running the setup with CPU turbo @ 4GHz for all cores without touching any voltage controls.
Only other thing I've changed from the BIOS is turning on XMP profile for my 4+4GB of Corsair Vengeance LP.
I'm having a problem with this, computer tends to boot and immediately reboot and after forcing computer down and rebooting I've been greeted with overclock failed message (doesn't do this every time).
If I enter the BIOS and without any changes reboot the computer (from BIOS) my computer boots up fine and Windows 8.1 runs completely stable without any kind of problems, stress tests pass fine and games run like they should and temperatures are fine.
This behavior is odd as my 2500K ran 4GHz turbo without touching volts perfectly fine. And this 4670K got higher default turbo clock.