The latest AGESA microcode update (AM4 1.0.0.3 ABB), which AMD has already distributed to motherboard manufacturers, removes support for the PCI Express 4.0 interface from all motherboards with Socket AM4 that are not based on the AMD X570 chipset.
Many motherboard manufacturers have implemented support for the new faster interface on their own on motherboards with the system logic of the previous generation, that is, AMD B450 and X470. In some cases, full support for the new interface was implemented, and in some, for example, ASUS, partial. However, she was still there.
However, these efforts of motherboard manufacturers ran counter to AMD's own strategy to promote the most modern X570 platform, the key feature of which is support for the PCI Express 4.0 interface. And AMD clearly wants this feature to remain exclusive to new motherboards.
Gigabyte has already released new BIOSes for their motherboards that use ABB's AGESA AM4 1.0.0.3. In the description for these new versions, the company notes that with them the board will lose support for PCI Express 4.0. Another feature of the new firmware version is a fix for problems with launching Destiny 2 on Ryzen 3000 systems. Other motherboard manufacturers are not in a hurry to release similar updates, but should eventually do so.
Therefore, when updating the BIOS, you should pay attention to its description. In general, we note that updating the BIOS to the latest version is not at all necessary, so PCI Express 4.0 support on older motherboards can be retained.
Source: 3dnews.ru