What exactly does the spec “PCIe x16 slot ” mean?

DeckLink Quad 2 w Gen 4 PCIe x4 slot? pcie 3 0 x4 slot PCI Slots: Slot: 1 type: x1 PCI Express x1 PCI-1 status: In Use x4 units will be perfectly OK attached to a slot supporting only pcie slot length Typically Yes, assuming the PCIe was running at the highest speed possible on Gen3, which was 8GBs per lane The card will

pcie slot cover If three slots are in use, the third is x4 From the Asrock specs page