Searching for B550 or X570 M.2 slots compatible with bifurcation in every or most slots—Asus Hyper M.2 x16.
Searching for B550 or X570 M.2 slots compatible with bifurcation in every or most slots—Asus Hyper M.2 x16.
Hello, you're seeking a board with bifurcation options for x16 slots to improve compatibility. You want to fit your Hyper M.2 into either x16_1 or x16_2 without issues. It's tough to tell which boards support this feature, but an ASUS ROG Strix B550 XE Gaming could be a good fit. Let me know if you need more details!
The standard 2nd PCIe port typically features 4 or 8 lanes, while no motherboard offers an 16-port configuration in the lower slot. The B550 chipset supports up to 10 lanes, though manufacturers might opt for just 2 to accommodate additional SATA connections. The x570 chipset can handle up to 12 lanes as well, following the same general rule. Generally, the top PCIe x16 port receives 16 lanes from the CPU. A few motherboards include two PCIe x16 slots, allowing flexibility—switching to x8 slots when needed, or using the first slot for x16 if the second is free. In theory, the lower x16 port can be divided into four groups of four lanes, enabling four M.2 drives on an ASUS card, depending on BIOS support and partitioning options. The bottom x16 slot is most commonly PCIe x4 or x2, since only four lanes are needed for the second M.2 connector, leaving eight lanes for x1 slots and the lower x16 port. However, the card cannot automatically generate 16 lanes if the slot actually has just four lanes, or if it’s limited to two lanes on certain boards. This limitation is confirmed by the diagrams for B550 and x570 chipsets.
I'm explaining that no chipset currently provides enough PCI-E lanes to fit 16 in the second slot. Typically there are four PCI-E lanes for the M.2 connector and a few extra x1 slots, leaving less than eight available. Most boards therefore use PCI-E X4 in the lower slot. Options like Threadripper offer at least sixty PCI-E lanes if you need many. Refer to the images I shared earlier.