With the launch of the beta BIOS by ASUS and ASRock, Zen 3 support has been brought to the older B450 and X470 boards well ahead of the slated date. However, it appears that the said update (AGESA v2 18.104.22.168) also brings a little surprise along with it: Smart Memory Access (SAM) is now also available on the 400 series boards, only with a Ryzen 5000 CPU and RX 6000 GPU though.
At the moment, only ASUS and ASRock boards support Zen 3 and SAM on the older B450 and X470 motherboards, but this proves that the rest of the board partners will also be bringing both features to their older offerings in the coming months. There’s a chance that SAM support will also come to the Ryzen 3000 CPUs.
AMD has already confirmed that it’s working with Intel and NVIDIA to allow SAM in parallel with the former’s CPUs and the latter’s GPUs, respectively. Smart Memory Access is actually part of the PCIe 3.0 spec and is technically called resizable BAR.