You can try and go for 1.35v vcore, can probably get around 4.5ghz out of that. Just set the multiplier to 45x and it will be 4.5ghz. If its not stable reduce to 44, if it is stable you can go one step up.
For a beginner I don't think you should go much higher than 1.38v max, and try to keep temps under 80c.
For a beginner I don't think you should go much higher than 1.38v max, and try to keep temps under 80c.