Nvidia has released a tool that will let users update the Video BIOS (VBIOS) on its Founders Edition RTX 3000 series graphics cards. This VBIOS update will enable PCIe Resizable BAR (PCIe ReBAR) support on it. All of Nvidia's 30-series GPUs from the RTX 3060 Ti up to the RTX 3090 are compatible with this update. While you may be wondering what happened to the RTX 3060, it's because it already comes pre-installed with the compatible VBIOS. Alongside Nvidia, most of its partners have also released similar tools for doing the same thing on their own respective models.
The PCIe Resizable BAR function allows the CPU to have full access to the entire memory of the GPU, whereas typically a processor can only address 256MB for compatibility with 32-bit OSes. As a result, thanks to the entire VRAM now being available, requests from the CPU can be performed in parallel instead of sequentially, which in turn improves the speed of their dispatch. It's claimed to be especially helpful nowadays since game assets keep getting bigger.
To ensure your graphics card is ready for the PCIe ReBAR VBIOS update, your motherboard BIOS must be updated to a version that will allow you to enable the feature. For example, AMD added support for it via the AGESA 184.108.40.206 firmware. Likewise, you'll also have to do the same for Intel motherboards. Individual motherboard vendors, like ASUS or MSI, and others, also have to be kept in mind, and support from them may vary.
When it comes to CPUs. AMD's Ryzen 5000 series processors will support the feature and it remains to be seen if Nvidia also enables it on 3000 series CPUs as AMD has done. For Intel, the 10th gen 'Comet Lake-S' and 11th gen 'Rocket Lake-S' processors have support for ReBAR.
The latest GeForce WHQL graphics driver version 465.89 is said to be optimized for the feature and Nvidia claims up to a 12% performance improvement. This driver will also allow you to verify if ReBAR is enabled on your graphics card or not by visiting the "Display" section of the "System Information" tab inside the Nvidia Control Panel.
The Nvidia Founders Edition VBIOS update tool as well as those from partner models can be found on this page. Finding some of these may be a little tricky as you'll have to visit the support section of your respective vendor model where you should find the necessary VBIOS. If you run a GALAX or Gainward graphics card, you will have to visit their respective Chinese websites where you'll find the VBIOS update.