Some ASUS X470 and B450 Motherboards Support PCIe 4.0

PCIe 4.0 support on non-X570 chipset motherboards is possible after all. Despite AMD denying any possibility of this happening back at Computex 2019, ASUS is saying otherwise. A list of various ASUS X470 and even B450 motherboards have been unearthed by Chinese tech site MyDrivers, showing PCIe 4.0 support. At least partially for some.

This rumour was further bolstered when frequent leaker @momomo_us has also tweeted out similar information. Although it looks like it is from a different document, it nonetheless echoes the same PCIe 4.0 list support.

Which B450 and X470 Motherboards Have PCIe 4.0 Support?

PCIe 4.0 support is available in three types: x4, x8 and x16. Denoted by a square, triangle and a circle, respectively in the chart above. Each motherboard also varies on whether the M.2 or PCIe slot supports Gen 4.0. Some have support for both.

From the chart, only the TUF X470-PLUS GAMING motherboard offers full PCIe Gen4 x16 support on the first PCIe expansion slot among all the X470 boards. Both ROG VII Hero and ROG STRIX X470-I only have Gen 4×4 support via M.2 slot, but do not support it for their expansion slot. Meanwhile, the PRIME X470-PRO and ROG STRIX X470-F have Gen 4×8 support for the PCIe expansions lot, and supports Gen 4×4 via M.2.

Meanwhile, there are actually a lot more B450 motherboard choices that support Gen 4×16 via PCIe slot. Only the ROG STRIX B450-E, B450-F, and B450-I do not have it. However, they support PCIe Gen 4×4 via M.2 like the rest of the ASUS B450 lineup.

How Is This Possible on X470 and B450?

Full support for PCIe 4.0 requires a BIOS update, although this isn’t really surprising. The function comes with the use of a Ryzen 3000 CPU rather than the chipset itself.

Should AMD decide to restrict this functionality via an AGESA microcode update, they could. ComputerBase.de has also confirmed this with ASUS as well.

So officially, actual Gen 4 support on X470/B450 is technically a workaround so far exclusive to ASUS boards. Although from their tests, the PCIe Gen 4×16 performance on an X470 motherboard is similar to that of an X570 with a Ryzen 3000 CPU.