can you run pcie 4.0 in 3.0 slot: Will this card work in a PCI-E 3.0 slot? – Q&A – Best Buy. PCIe Slots & Lanes Explained: Choosing the Right Connection (Fast ... . Can I Use a PCIe 4.0 Graphics Card in a PCIe 3.0 Slot? - TechReviewer.
A PCIe 3.0 GPU card connected to a PCIe 4.0 (or, in the future, a PCIe 5.0)
slot will behave like a PCIe 3.0 GPU card due to forward and backward compatibility.
However, PCIe devices are generally compatible with newer versions of the PCIe standard, so a PCIe 3.0 device can be used in a
PCIe 4.0 slot, for example, albeit at a lower data transfer rate.
You can use a PCIe 4.0 SSD in a PCIe 5.0 slot, and it will work just fine, at PCIe 4.0 speeds. Similarly, a PCIe 5.0 SSD can be used in a PCIe 4.0 slot, but again, its performance will be limited to PCIe 4.0 levels.