Hello,

I am working on the ATX power supply to my RepRap. I have EVGA 500W and there are 2 4-pins CPUs. Should I use one or both of them to get 12V to my RAMPS board?

I've looked at the diagrams that reprap.org provide, but I am doing it a bit differently.

Both will be best, since ramps uses two power connectors you can connect one to each of ramps board.

Be sure that both deliver same power, if not use the most powerful for your heated bed.