PCIeSlots

PCIe slots, or PCI Express slots, are expansion interfaces on modern computer motherboards used to connect PCIe cards such as graphics cards, storage adapters, and network devices. They provide a point-to-point serial connection that offers high bandwidth and low latency compared with older expansion buses. Slots come in widths designated by the number of lanes: x1, x4, x8, x16 (and occasionally x32). The physical size matches the width, and a card can operate in a larger slot at its own width, but not the other way around.

PCIe generations determine the speed of each lane. PCIe 1.x delivers 2.5 GT/s per lane; 2.x 5 GT/s; 3.x 8 GT/s; 4.x 16 GT/s; 5.x 32 GT/s. Practical throughput per lane grows accordingly, so a PCIe 3.0 x16 slot can provide up to about 15.75 GB/s in one direction, and PCIe 5.0 x16 up to about 32 GB/s per direction. PCIe 6.0, introducing PAM-4 signaling, further increases per-lane bandwidth, with hardware gradually entering the market.

Compatibility is a hallmark of PCIe. The standard is backward compatible, so newer devices can operate in older slots at the lower supported speed, and wider slots can accommodate smaller devices (for example, a PCIe x4 card in an x16 slot) with bandwidth limited to the card’s width.

Common uses include graphics cards, NVMe solid-state drives, network adapters, and various I/O or capture cards. Slots provide power from the motherboard for low-power devices; high-end GPUs or multi-PCIe cards may require additional power connectors.