The Overclocking Key groups the individual 12V-rails to a single 12V-rail. You can enable the overclocking function permanently by setting the jumper provided directly at the power supply. Or you can enable the overclocking function by pressing the switch on the slot cover provided as needed. The overclocking key is connected to the power supply using the connector labeled accordingly. When you switch on the overclocking function at the slot, a LED lights on the slot cover switch.