Question, concern PCIe PCIe

Should you buy a PCIe or SSD? can i use m 2 pcie 4 0 in 3 0 slot PCIe slots feature the same pin layout and thus are forwards and backward-compatible However, a PCIe card slotted into a PCIe slot will can i use a pcie 40 nvme in a 30 slot So you will only see x8 on that PCI slot if you use the M2C connector Note that is the same speed as PCIe4x16 so you aren't really

candy dreams slot If two SSDs are installed in a “Dual NVMe PCIe adapter” and the adapter is plugged in either PCIe slot2 or slot7