MSI has unofficially added Re-Sizable BAR support (AMD’s Smart Access Memory) to Intel 400-series boards as well as NVIDIA’s RTX 30-series GPUs on both platforms. You can now enable Re-Sizable BAR if you own a 400-series Intel board (Z490, H470, B460, or H410) with a 10th Gen CPU and an AMD Big Navi GPU or an NVIDIA RTX 30 series GPU.
The same is true for AMD’s 400-series boards. However, here support will be limited to the Ryzen 5000 boards, with GPU support on both Radeon RX 6000 as well as the RTX 30-series GPUs.
At present, support for SAM on these boards is unofficial. This means that the feature is likely in beta mode and there may be bugs or instabilities. Formal support is expected early next year.
Re-Sizable BAR allows the CPU to leverage the full PCIe bandwidth to interact with the GPU. Traditionally, this has been done using 256MB windows. Although this hasn’t been a bottleneck as each application can open multiple 256MB windows and move them around in the VRAM as needed, it can at times latency gaps which can leave some additional performance on the table.