Lexar 4TB NM790 PCIe Gen4 NVMe M.2

Only the specifications this product actually carries.

NVMe

NVMe (Non-Volatile Memory Express) is the protocol modern SSDs use to talk to the system over PCIe, replacing the older AHCI protocol designed for spinning disks. NVMe drives, almost always in the M.2 form factor, are several times faster than SATA SSDs in sequential transfers and much faster at handling many simultaneous requests. NVMe has become the default for new builds, and its price per gigabyte now overlaps with SATA on many capacities.

M.2 2280

M.2 is the compact card form factor for SSDs that plugs directly into a motherboard slot, and 2280 describes the dimensions: 22mm wide and 80mm long, the most common size for desktops and laptops. Other lengths exist, notably 2230 for handhelds like the Steam Deck. An M.2 slot may carry NVMe, SATA, or both, and a drive must match what the slot supports.

PCIe generation (Gen3, Gen4, Gen5)

The PCIe generation of an NVMe drive sets its maximum bandwidth: roughly 3.5 GB/s for Gen3, 7 GB/s for Gen4, and 14 GB/s for Gen5 on four lanes. A drive runs at the lower of its own generation and the slot's. Gen4 covers gaming and general use with no perceptible difference for most people; Gen5 carries a price premium and runs hot enough to usually need a heatsink. Buying a generation beyond what the workload uses is a common way to overpay for storage.

Sequential read and write speeds

The headline speeds on an SSD listing, such as 7,450 MB/s read, describe large sequential transfers under ideal conditions. They are the numbers that separate PCIe generations, and they are the least representative of everyday use, where small random reads dominate and most modern drives feel similar. Two drives with different headline speeds but the same generation and NAND type usually perform indistinguishably for gaming and desktop work.