NVIDIA GeForce RTX 20 & GTX 16 “Turing” GPUs Get Unofficial Resizable BAR Support

The unofficial NVStrapsReBar UEFI driver has enabled Resizable BAR support on NVIDIA GeForce RTX 20 & GTX 16 "Turing" GPUs.

Resizable BAR is a feature that has become a staple of the industry ever since it was announced a few years back. The technology which is part of the PCI spec allows the CPU to have access to the entire GPU memory space through the PCIe interconnect, thus removing any bottleneck & offering higher performance.

While initially supported on certain GPUs and motherboards, Resizable BAR support has extended to lots of older platforms but it looks like some of the most popular mainstream GPUs were lacking this support such as NVIDIA's GeForce RTX 20 & GTX 16 "Turing" GPUs. NVIDIA has even stopped the production of these GPUs but several GeForce gamers are still using them since they can be bought off the used markets for dirt-cheap rates and still deliver decent performance. We recently reported how the "GeForce GTX" era ended this year.

Once again, due to their popularity and usage, these older NVIDIA GeForce RTX 20 & GTX 16 GPUs can still benefit from Resizable BAR and since there's no official driver or UEFI support, an unofficial UEFI driver known as "NVStrapsReBar" has been made to enable such support. It is reported that older GeForce 10 "Pascal" cards are not supported but RTX 20 & GTX 16 series GPUs are. A range of configurations were tested and it looks like the Resizable BAR support is indeed working.

Yes, this is how it works for Turing GPUs (GTX 1600 / RTX 2000).

(some ideas to get it working without UEFI modding have circulated, but may not be technically possible and nothing is implemented.)

It's ususally the video BIOS (vBIOS) that should enable ReBAR, but the vBIOS is digitally signed (NVIDIA vBIOS is also encrypted) and can not be modified by modders and end-users (is locked-down). The motherboard UEFI image can also be signed or have integrity checks, but in general it is thankfully not as locked down, and users and UEFI modders often still have a way to modify it.

For older boards without ReBAR, adding ReBAR functionality depends on the Above 4G Decoding option in your UEFI setup, which must be turned on in advance, and CSM must be disabled.

Check issue #1 for a list of known working GPUs (and motherboards).

via NVStrapsReBar

The full guide to enable Resizable BAR for the older NVIDIA GPUs is mentioned here. While the tech has benefits in offering increased performance, there are certain instances where enabling BAR can lead to no performance gains on worse, even some performance loses (marginal at best) so you'll have to test out whether the game you are playing takes advantage of Resizable BAR support or not.