RX 580 NITRO+ 8GB runs only PCIe x1

The number represents the number of lanes in the PCIe slot For example, a PCIe x1 slot provides one lane and transmits data at 1 bit per cycle

The number after the x tells you how many lanes that PCIe slot has A PCIe x1 slot has one lane and

pcie m2 slot slot and an old 750ti for the host in a gen3 4x 2-AEkey to PCIE X1 Adapter Board Extension Cable Supports PCI-E x1 Riser Adapter

pcie x16 expansion slot 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-