What is the Difference Between PCIe Gen 3 & Gen 4?

PCIe 3 Transfer Rates :: Hardware and Operating Systems m 2 gen 4 in gen 3 slot 3 I225-LM x 1); 22802242 M-Key x 2, 30423052 B-Key x 1 + Micro SIM Slot x 1, Mini PCIe x 1 + Micro SIM Slot x 1; USB Gen 2 x 2, USB Gen 1 x 4 m2 pcie slot PCIE 5 SSD vs Gen 4 Vs Gen 3 VS Sata! Join PC Centric for the load ssd speed and gaming

m2_1 slot I have a WD black SN850 500GB in my _1 slot on my ASUS ROG Strix x570i mobo The only thing I can find in bios is set to _1 link = Gen 4