What is the difference between PCIe Gen 3 and PCIe Gen 4?

Here's the best way I've found and seen of modifying a PCIE x1 slot to fit a full-sized x16

Go in to BIOS and Set PCIE to AUTO or Gen 4 it may be getting hung up on the gen 5 PCIE slot So boot to bios from second slot

pcie slot dimensions It is used for GPUs mostly as well as SSD cards PCI Express x16 Slot – This is the largest and used for high-performance GPUs How Does PCIe Slot Work?

pcie slot size The only way to add a GPU is via a PCIe x16 slot because, as mentioned previously, the majority of GPUs are designed to utilize 16 PCIe