Understanding PCIe Bifurcation on ASUS PROART X870E-Creator WiFi

On the X870E ProArt, the chipset handles things nicely. You have 16 lanes for PCIEX16_1, which can yield flexibility if you're using cards that require fewer lanes. The first two slots provide x8 lanes for dual GPUs, which actually frees up the remaining x8 lanes for other uses like additional M.2 drives or the PCIEX16_3 slot. So yes, installing something in PCIEX16_1 and then a card in PCIEX16_2 will still allow PCIEX16_3 to function properly, as long as not all lanes are used up. It's all about that lane management setup!

Forget bifurcation for a second! Just check out the motherboard specifications on the ASUS site; it explains how the expansion slots function. With your CPU, you have 24 lanes to play with after accounting for the 4 lanes for communication with the chipset. When you install devices, the motherboard manages how those lanes are assigned. For example, installing two GPUs will typically drop their performance to x8 each, but you'll still have the capacity to install something in PCIEX16_3 as long as your configurations don’t max out the lanes.

If you fill the M.2 slots, be aware that those lanes come out of the motherboard's total pool. Given that you're likely to have only two NVMe drives and a GPU, you shouldn't run into lane exhaustion unless you max out the devices. If you decide to use that Asus Hyper M.2 X16 card later, remember that usage will also impact how the lanes are shared between your faster options.

The lanes allocated are determined by what's plugged in. Your setup indeed allows for flexible use of the slots, with parallel lane-sharing capabilities. If you configure your slots correctly, there’s no reason you can’t utilize them for the intended peripherals without performance loss—just check the motherboard manual for optimal configurations as it has specific guidelines on lane splitting and allocation.

When using a Ryzen 9000 or 7000 CPU, you have 28 PCIe lanes total, with 4 reserved for the chipset. If you plug a GPU into PCIEX16_1, it takes 16 lanes. This leaves you 12 lanes available. The second PCIEX16_2 slot can then work at x8 if you install another GPU, while the last slot, PCIEX16_3, would operate at x4 if you connect something there. But if you use the M.2 slots, that could affect the lane distribution, depending on how many peripherals are using the lanes. Basically, the system dynamically splits the lanes based on what's plugged in.

Bottom line: you can use PCIEX16_2 and PCIEX16_3, but be mindful of lane allocations, especially with M.2 SSDs!