Bifurcation
PCIe Bifurcation
PCIe bifurcation is a motherboard and CPU feature that splits a single physical PCIe slot (usually x16) into multiple, smaller, independent logical lanes (e.g., two x8, four x4). It enables running multiple devices, such as NVMe SSDs or GPUs, from one slot. It's not one of the things that can boost your frame rates, affect your CPU or GPU performance[1]
For example, you can divide a PCIe x16 slot into multiples of eight or four, which means it can support the following configurations:
- x8 / x8
- x8 / x4 / x4
- x4 / x4 / x4 / x4
Each lane 'split' can behave like an independent PCIe connection if your board supports it. Primarily used to install multiple M.2 NVMe drives via an adapter card, or to split a GPU slot to accommodate other peripheral cards.
Requires support from both the motherboard (BIOS/UEFI) and the CPU. Bifurcation divides lanes in the BIOS/UEFI, allowing the motherboard/CPU(actual bifurcation occurs at the CPU and chipset levels) to recognize and manage each split group as a separate device. That's why not all motherboards or BIOS/UEFI versions support PCIe Bifurcation. common in most high-end boards, it's not unusual for mid-range boards.
With two MCIO to PCIe adapter, like 2x MCIO 8i (74-pin) to PCIe x16 adapters to enable connecting high-speed PCIe 5.0 devices (GPUs/NVMe) via two SFF-9402 MCIO cables, providing full x16 bandwidth (x8+x8), These adapters often feature a 6-pin PCIe power connector, with the features of motherboard bifurcation support (x8x8)
Examples
This ICY Dock URL shows an example how to setup PCIe Bifurcation in BIOS