Resizable BAR is now available for NVIDIA's full RTX 30 desktop product stack, as the company promised earlier this month. Resizable BAR is available for most modern AMD and Intel chipsets and processors, including Zen 3 and Comet Lake-S CPUs. NVIDIA has expandable Resizable BAR support to 17 games, too.
https://www.notebookcheck.net/NVIDIA-brings-Resizable-BAR-to-all-RTX-30-desktop-cards-via-a-VBIOS-update-performance-boost-now-available-for-17-games.530306.0.html