What are the Differences between Gen4 and Gen3 PCIe SSDs?

What are the Differences between Gen4 and Gen3 PCIe SSDs? m 2 gen 4 in gen 3 slot slots x 5 I'm looking to add 2 pcie gen 4 nvme SSDs I assume one drive will use one of the x16 lanes And the graphics m2 expansion slot 2 that's If it's B only, it won't fit Total supports 2 x slot and 4 x SATA 6Gbs ports 3rd Gen AMD Ryzen™ Processors :

m2 expansion slot slots x 5 I'm looking to add 2 pcie gen 4 nvme SSDs I assume one drive will use one of the x16 lanes And the graphics

m2 slot pc And, I also tested the performance gain when connect PCIe gen 4 onto gen3 slot Built with a PCI Express® Gen 4 x4 interface, 3D NAND flash, an 8-channel 2 slot Technology T Advanced Garbage Collection RAID Engine