PCI Express

PCI Express (PCIe) is a high-speed serial expansion bus standard that connects processors and chipsets to devices such as graphics cards and storage drives. It uses configurable groups of point-to-point lanes rather than a shared parallel bus.

PCI Express lane: A PCIe lane is a full-duplex pair of serial communication paths that carries data between two PCIe devices. Lane count determines the link’s potential bandwidth; common configurations include x1, x4, x8, and x16.
Peripheral Component Interconnect: Peripheral Component Interconnect (PCI) is a parallel computer bus standard that preceded PCI Express. PCIe replaced PCI’s shared parallel signaling with serial point-to-point links.
Graphics card: A graphics card is an expansion device that renders images and video, often using a dedicated graphics processor. Discrete graphics cards commonly use wide PCIe links to exchange data with the host.
Accelerated Graphics Port: Accelerated Graphics Port (AGP) was a computer expansion interface designed primarily for graphics cards. AGP was displaced by PCIe as graphics platforms moved to a general-purpose serial expansion link.
PCI Express packet: A PCIe packet is a formatted unit of information transmitted across a link, including transaction, data-link, or physical-layer packets. PCIe carries requests and data as packets rather than as signals on a shared parallel bus.
PCI Express form factor: A PCIe form factor specifies the physical dimensions and connector arrangement of a PCIe card or slot. Physical slot size and electrical lane count are related but not identical.
Non-Volatile Memory Express: Non-Volatile Memory Express (NVMe) is a storage protocol designed for nonvolatile memory devices, commonly SSDs. NVMe SSDs commonly use PCIe as their transport to the host.
Universal Serial Bus: Universal Serial Bus (USB) is a standard for connecting and powering external peripherals. USB targets general external peripherals, while PCIe primarily connects components within a computer.
PCI Express link training: PCIe link training is the startup process through which connected ports establish a link and agree on its operating parameters. Training lets a link negotiate its lane count and supported signaling rate.
PCI Express configuration space: PCIe configuration space is a structured set of registers used to identify and configure devices and their capabilities. Firmware and operating systems inspect it to discover and configure PCIe devices.

Linked from 6 pages