Check this video:
Z690 rebar
Advanced>Chipset>Above 4G Decoding Set to Enabled>Re-Size BAR Support
"Resizable BAR is an optional PCI Express interface technology. As you move through a world in a game, GPU memory (VRAM) constantly transfers textures, shaders and geometry via many small CPU to GPU transfers.
With the ever-growing size of modern game assets, this results in a
lot of transfers. Using Resizable BAR, assets can instead be requested as-needed and sent in full, so the CPU can efficiently access the entire frame buffer. And if multiple requests are made, transfers can occur concurrently, rather than queuing. "