PCIe - PCIe in Industrial Computers: Slots, Lanes and Speeds

What PCIe Actually Is

PCIe (Peripheral Component Interconnect Express) is the high-speed serial expansion bus used inside virtually every modern computer. Instead of the old shared parallel PCI bus, PCIe uses independent point-to-point lanes — each lane is a pair of differential signalling wires, one direction for transmit and one for receive. Devices negotiate automatically, so a card built for fewer lanes or an older generation still works in a wider, newer slot, just at the lower common speed.

Lanes are grouped into standard link widths: x1, x2, x4, x8 and x16. A graphics card typically wants x16, an NVMe SSD wants x4, while a network card, serial card or capture card is usually comfortable at x1 or x2. That flexibility is why PCIe is the default expansion path for almost any add-on function.

Generations and Real-World Bandwidth

Each PCIe generation doubles the per-lane transfer rate, and effective throughput also depends on encoding overhead (8b/10b in Gen 1–2, 128b/130b from Gen 3 onward).