In terms of the motherboard requirements for the NVIDIA GeForce RTX 3090, you will need a 750W power supply if you pair the card with a mainstream Core i5/i7 processor or Ryzen 5/7 processor. Those requirements jump to 850 Watts for Intel Core i9 and Ryzen i9 processors with peak requirements of 1000 Watts for Intel HEDT and AMD Threadripper processors.