Why would a PCIe x16 slot be limited to PCIe x1 card?

pciex1 slot   Dan pciex16 slot configuration

PCIe x1 slot can support all types of wireless cards, including the latest Wi-Fi 6 protocol However, a PCIe x1 slot can only support 1 Gigabit

Slot power · x1 cards are limited to A at +12 V and 10 W combined · x4 and wider cards are limited to A at +12 V and 25 W combined · A full- Here's the best way I've found and seen of modifying a PCIE x1 slot to fit a full-sized x16 card

borderlands 3 artifact slot By specification, all PCIe cards are backwards compatible with the lowest bandwidth x1 lane slots If the x1 slot is designed with an open end, PCIe interface, slot and mounting multiple cards in one computer Computer motherboard may have PCIe slots compatible with x1, x4, x8 and x16 When users need