https://wccftech.com/msi-enables-resizable-bar-support-on-intel-z490-boards-with-nvidia-geforce-rtx-30-gpus/

Over the course of a few weeks, we have seen board makers enable Resizable-BAR support on Intel platforms. The feautre which was first introduced under the SAM (Smart Access Memory) by AMD is now being adopted by every major board manufacturer with some even extending beyond official support. Today, we can confirm from our sources that MSI is the first board maker to have enabled Resizable-BAR support (unofficially) on Intel 400-series motherboards and NVIDIA GeForce RTX 30 series graphics cards.

Resizable-BAR has many advantages for increasing the performance in a range of apps including games. Based on what we know so far, BAR essentially defines how much discrete GPU memory space can be mapped and today's PCs are typically limited to 256 MB of mapped memory. AMD claims that with SAM (Smart Access Memory), they can access all of the GPU memory, removing bottlenecks to allow for faster performance.