Voltage modding is very necessary for the maxing out of hardware. This is a detailed guide.

Voltage modifying boards and cards can be quite scary for those new to it.
However with practise, it can become quite easy. It is definitely very useful
when you need to overclock your CPU, memory and video card.

Voltage modifications typically involve adjusting the resistance across certain
SMD components as voltages are always regulated by the values of resistance. A
lot of times, it involves changing the resistance of a certain pin of a
regulator chip as different pins serve different functions, and normally one of
these pins feedback the voltage sensed to the chip and changing the resistance
on this pin can change the voltage that is fedback.

A usual voltage mod will involve something like this:

A wire that is connected to a pin will run to a variable resistor. There will be
another wire running from the variable resistor and this will connect to a
grounded spot. By adjusting the variable resistor, you will be adjusting the
resistance of the pin.