Just set cpu multiplier to 20x, leave the bus speed at the default 200, and you'll get 4.0 Ghz.
Enable cool and quiet and disable coreC6state.
Run prime95 for 15 minutes and see if you'll get problems.
If you get an error or bluescreen, you need to increase cpu vcore.
I haven't overclocked my fx6100 in a long time so I dont remember the settings exactly.
I think you'll need at least 1.36 cpu vcore for 4.0 Ghz.
You'll need somewhere around 1.4 to 1.45 vcore for 4.5 Ghz.