When attached to a motherboard's PCIe x16 slot, a card such as the GeForce RTX 4080 can draw up to 75W from the +3.3V and +12V rails (3.3V x 3A + 12V x 5.5A). This is the maximum amount specified ...
If so, the top slot likely runs at PCIe x16, meaning 16 data lanes, which is ideal for high-bandwidth add-ins like a graphics card. And if you have a second slot, it likely runs at PCIe x8.