PCIe lanes are data pathways that connect your CPU and chipset to components like GPUs, NVMe SSDs, and expansion cards. Each lane consists of two pairs of wires for sending and receiving data simultaneously. Slots are labeled by their lane count — x1, x4, x8, or x16 — with more lanes providing more bandwidth.
Most users need 16 lanes for a GPU and 4 lanes for a primary NVMe SSD — that's 20 lanes minimum. If you're adding more NVMe drives, capture cards, or network cards, you'll use additional lanes through the chipset. CPUs provide 20–24 usable PCIe lanes, and the chipset expands that further.
Lane sharing is when two or more slots on a motherboard use the same PCIe lanes. For example, installing an NVMe drive in a shared M.2 slot might cause the GPU slot to drop from x16 to x8. This is a design trade-off — manufacturers share lanes to offer more slots than the CPU can directly support. MoboMaps shows exactly which slots share lanes on each board.
If it's an NVMe M.2 SSD, yes — it typically uses 4 PCIe lanes. These lanes may come directly from the CPU (fastest, often Gen5 or 4) or from the chipset (Gen4 or Gen3). SATA SSDs use the SATA and use Gen3 lanes. Which M.2 slot connects where varies by motherboard — our maps show exactly how each slot is wired.
CPU lanes connect directly to the processor and offer the lowest latency and fastest speeds — currently the only source of Gen5 bandwidth. Chipset lanes route through the motherboard's chipset, which connects to the CPU via a narrow uplink (x4 on AMD, x8 on Intel). The chipset expands this into many more connections for USB, SATA, additional M.2 slots, and add-in cards. Devices on chipset lanes share that uplink bandwidth.
In most cases, the difference is minimal — typically 1–4% in gaming. At higher resolutions like 1440p and 4K, the GPU becomes the bottleneck rather than the PCIe connection, so the impact shrinks further. PCIe Gen5 x8 provides the same bandwidth as Gen4 x16. For the vast majority of gamers, x8 is more than enough.
MoboMaps is a free interactive tool that visualizes PCIe lane layouts on motherboards. It shows how lanes are routed from the CPU and chipset to every slot, so you can see which components share bandwidth before you buy. Filter by brand, chipset, form factor, and more to compare boards side by side.
MoboMaps currently covers 200+ AMD AM5 motherboards across X870E, X870, X670E, B850, and B650 chipsets from ASUS, MSI, Gigabyte, and ASRock. New boards are added regularly, and Intel support is coming soon.