What kind of things, aside from a GPU, can you put into ...
PCIe x1: These are the smallest PCIe slots, used for almost any other cards like average network adapters and USB expansion cards.
PCI-Express to Dual PCI Adapter X16 PCIe Slot Expansion Card USB ...
PCIe passthrough is only supported by a specific set of PCIe cards, which must be installed in specific PCIe slots. The following table lists the QNAP PCIe cards that are compatible with the PCIe card interface on your device.
PCIe Bifurcation – What is it? How to enable? Optimal Configurations ...
Although PCIe x1 slots have a PCIe lane, they are still useful, and in some cases, use PCIe x1 slots instead of larger slots such as PCIe x16 to maintain optimization.