I not long sent the same system to a family member who wanted to play CSGO.
It was running 4.7Ghz stably, with 1.35v using a D14.
You can easily use 1.35v as that is listed as maximum safe voltage. Also set LLC to high (or 1 down from the max) and VCCIO to 1.18v (not 1.8!
). Disable CPU spread spectrum and leave everything else at auto including PLL.
Use Realbench to stress test (as it also stresses GPU subsystem) 15min at a time and start from say 4.2Ghz and go up in 100mhz interments until you get instability. Then drop down 100mhz and do an extended test in Realbench, CBr20, x264 stabilty...
Also make sure you've updated to the latest bios before starting.
If you've got a real dog of a CPU then it won't do 4.5Ghz but most will with these settings. If you get addicted to tweaking you can increase the Phase Control to max (Extreme I think) and CPU Current Compatibility to 130%. PLL is funny because tweaking it slightly down i.e. 1.70v as well as slightly up can be beneficial but unless you're going for a 5Ghz then I'd stick to basics.