How many PCIe slots do I need? Is PCIe Gen 4 worth it?

List of Motherboards with 4 PCI-Express x16 Slots pcie 4 slot Hi, Was wondering if anyone tried using a Gen 4 Storage AOC in a Gen 5 slot? Thinking of using a card like the AOC-SLG4-4E4T (PCIe x16 to 2x pcie 4 in pcie 3 slot ssd PCIe x4: This slot supports four lanes of data transfer, providing higher bandwidth than the PCIe x1 slot It is commonly used for storage devices such as SSDs

pcie 4 ssd in pcie 3 slot 2 slots, which will be PCIe X4 Gen 34