PCI Express x16 graphics card in a PCIe x16 slot?

While not optimal, what happens if you put the Startech card into PCIE_4? Will it work then even though your GFX card will only be at 8X? Merely

You can put smaller cards in a larger slot, but not the other way around So a 1x will fit in a 16x or 8x slot but a 8x won't fit in a 1x

candibet slot PCIe lanes are limited on consumer platforms, so odds are if you have two x16 slots, they share bandwidth, and having a GPU in one will limit

candy jar slot So 5-6 SATA drives can potentially over-saturate that PCIe slot, but in real-life I doubt you'd ever actually do so You could run the 850