Also known as: PCIe, PCI-E
PCI Express (PCIe) is the high-speed serial expansion standard that connects add-in cards — graphics, storage, networking — to a computer’s chipset and CPU.1
Overview
PCIe replaced older shared parallel buses with scalable point-to-point links built from one or more lanes, each a pair of differential wires in each direction. A slot is described by its lane count — x1, x4, x8, x16 — and each new generation roughly doubles per-lane bandwidth. Unlike a classic system bus, devices do not share one set of wires; each gets a dedicated link to a switch, so adding cards does not slow the others.
What it’s for
A GPU typically takes a x16 slot, while NVMe SSDs, network cards, and capture cards use narrower links. The slots and lanes live on the motherboard, routed through the chipset. In a high-throughput SDR rig, a PCIe slot is where you would add a fast capture card or an accelerator to feed wideband samples into the decode pipeline without starving the bus.
Sources
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PCI Express — Wikipedia, on the PCIe serial expansion standard, lanes, and generations. ↩