I was able to reach stable 4.4 GHz with (Asus Z87-A):
- Vcore 1.375 (IMPORTANT: use Fixed, not 'Adaptive' or 'Offset')
- Cache Ratio and Voltage at "Auto" (default)
- CPU Input Voltage 1.9
with my 4670K.
Started with the settings at the top of the page but got a BSOD with 3DMark instantly...