Definition
PCI Express (PCIe) is the high-speed expansion bus that modern computers use to connect add-in cards such as graphics cards, network adapters, and NVMe storage to the host system. It replaced the older parallel PCI and AGP buses with point-to-point serial links, which removed the shared-bus bottleneck and let bandwidth scale cleanly with each new generation.
Lanes and generations
PCIe organises bandwidth into lanes. A single lane is one differential transmit pair and one receive pair; slots are built as x1, x4, x8, or x16, with the number indicating how many lanes are wired. More lanes mean more bandwidth, and successive generations roughly double per-lane throughput: PCIe 3.0 delivers about 985 MB/s per lane, PCIe 4.0 about 1.97 GB/s, and PCIe 5.0 about 3.94 GB/s. A device negotiates the highest common generation and lane width its slot and the host support.
Why it matters for mining rigs
GPU mining rigs lean heavily on PCIe, but in an unusual way. A graphics card hashing on a memory-bound algorithm sends almost no data across the bus once a job is loaded, so the link can be throttled to a single lane without hurting hashrate. This is why miners run powered x1-to-x16 risers: a tiny x1 connection feeds the card while a separate cable delivers power, letting a single board host six or more GPUs spread out for airflow. ASIC miners, by contrast, rarely use PCIe internally, relying instead on simpler on-board serial buses.
For the physical slot that PCIe cards plug into, see edge connector, and for the broader idea of how components share a data path, see system bus.
In Simple Terms
PCI Express (PCIe) is the high-speed expansion bus that modern computers use to connect add-in cards such as graphics cards, network adapters, and NVMe storage…