Alleged ASUS X470/B450 PCIe 4.0 Compatibility Table Paints A Confused Picture
ASUS ROG Strix B450-F Gaming II AMD AM4 (Ryzen 5000, 3rd Gen Ryzen ATX Gaming Motherboard (8+4 Power Stages, HDMI 2.0b/DP,2 x PCIe 3.0 x16, USB 3.2 Gen 2 Type-C, BIOS Flashback,
B550 motherboard guide: ASUS and AMD bring PCI Express 4.0 to everyone with ROG Strix, TUF Gaming, and Prime - Edge Up
Pcie 4.0 on B450 : r/Amd
Did Asus enable pcie 4.0 on B450 motherboards, again ? : r/Amd
B450 pcie 4 support - CPUs, Motherboards, and Memory - Linus Tech Tips
Amazon.com: ASUS ROG Strix B450-F Gaming II AMD AM4 (Ryzen 5000, 3rd Gen Ryzen ATX Gaming Motherboard (8+4 Power Stages, HDMI 2.0b/DP,2 x PCIe 3.0 x16, USB 3.2 Gen 2 Type-C, BIOS
BIOS Update Enables PCIe 4 On AMD X470 Boards With Ryzen 3000
You may be able to get PCIe 4.0 on these ASUS X470 and B450 boards - HardwareZone.com.sg
ASUS B450 boards apparently support PCIe 4.0 now | guru3D Forums
AMD To Disable PCIe 4.0 Support In Final X470/B450 BIOSes After X570's Launch