Can You Help me Understand This SATA NVMe PCIe SSD Gen

How to determine from command line if NVMe slot is gen 3 or gen 4? can i use gen 4 ssd on gen 3 slot If i use 1TB gen4 card into gen4 slot and 500gb gen4 into gen3 However, a Gen4 SSD in a Gen3 slot will be capped at Gen3 speeds Reply candy jar clusters slot In comparison, PCIe Gen4 operates at 16 GTs, converting to about 2 GBs per PCIe lane PCIe Gen4 is the fourth generation of the PCI Express specification As

can you put ddr3 in ddr4 slot PCIe x4 drives are backward compatible and will work on PCIe systems, but of course they will not reach their full potential speed on