rx 550 recognizing pcie x16 slot as x8

pciex16 slot   Dan pciex16 slot configuration

if the slot is open like that, you should be good to go if it's not open, you could a) use another riser to adapt the x8 to x16, or b)

your i5-3470 works on PCIe natively, Optiplex 7010 has only one slot bound to CPU PCIe, others are linked via chipset  your i5-3470 works on PCIe natively, Optiplex 7010 has only one slot bound to CPU PCIe, others are linked via chipset

professional slot car racing PCIe x16 Gen expansion backplane with two slots The PCIe x16 Gen3 backplane has two PCI Express x16 slots, with one slot supporting the OSS target A x8 card will work in an x1 slot, but will be limited to x1 speeds A x8 card will also work fine in a x4 slot It will be limited to x4 speeds