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IT Support & Hardware · Foundational

PCI Express (PCIe)

A high-speed serial expansion bus connecting graphics cards, NVMe SSDs, and other cards to the motherboard.

Definition

PCIe uses point-to-point lanes, with slots in x1, x4, x8, and x16 widths. Bandwidth roughly doubles each generation: about 1 GB/s per lane for PCIe 3.0, 2 GB/s for 4.0, and 4 GB/s for 5.0 in each direction. Cards are backward and forward compatible, running at the lowest common generation and width.

Example

A PCIe 4.0 x4 NVMe SSD in a PCIe 3.0 slot works but at about half its maximum speed.

Exam tip

A smaller card fits in a larger slot (x1 card in x16 slot), but not the other way around.

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