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

The biggest and best PCI Express slot is the PCI Express x16 slot Pretty much the only thing that uses x16 slots outside of graphics cards is server-grade

PCIe x16 devices are not compatible with smaller PCIe slots such as x1, x4, or x8 slots, but some motherboards may have PCIe x16 slots that are electrically

pcie 4 in pcie 3 slot SuperSpeed Storage：PCIe x4 Connector; EZ-Latch：PCIe x16 Slot with Quick Release Design; Fast Networks：GbE LAN; Extended Connectivity：DP, HDMI; Smart

pci 4 in pci 3 slot You'll need to disable Nvidia HD audio, and plug the from the AV40s to your sound card