What are the top uses of PCIe x1 Slots?

What are the top uses of PCIe x1 Slots? pcie x1 in x16 slot P35 boards can only allocate x1 or x4 lanes to the second PCI-E slot Your card is definitely in X1 mode, GPU-Z doesn't truncate numbers like pcie 20 x16 slot Intel no longer supports PCIe x1 controller cards plugged into PCIe x16 slots starting from the Alder Lake desktop PCs, which are HP G9 platforms

pcie 20 x16 slot I cut open the back of a x1 slot on my motherboard to allow me to fit a full size GPU

pcie 4 m2 in pcie 3 slot Or will they only work on a PCI-Ex1 slot? Reason being I am looking at buying an MSI 990FXA-GD80 MoBo I want to use the second card slot Any PCI Express card of a smaller size will fit into a larger slot So an x1 card will fit in an x8 slot Please see the Wikipedia article