Pros and cons of overclocking NB and HT link

[full_out]

I have my FX-4100 overclocked to 4.7ghz and my NB and HT link at 2100mhz. What benifit would I see if I overclocked my NB and or HT link more? And do you have to overclock them to the same values at the same time? I've never got a straight answer on what these do, or if they are worth overclocking.
Thanks!

 

[full_out]

Thanks!!! I will try that

 

[satinsguard]

Gigabyte GA-990FXA-UD3

I have that board and I can overclock it to 2600MHz both the H/T and N/B together and have the voltage at auto.