About a month ago, NVIDIA announced that they would be offering Resizable BAR support for their RTX 30 Series laptop parts as well as desktop RTX 30 Series, and with their GeForce Game Ready Driver 461.72, they did just that. But for now, it’s a bit limited with only the mobile SKUs supported and a single desktop component, the RTX 3060.
In short, Resizable BAR removes the strict limitation on the amount of data that can flow between CPU and GPU memory and can sometimes significantly increase performance. Resizable BAR gained in popularity and recognition when AMD implemented Smart Access Memory when pairing a Ryzen 5000 Series CPU and a 500 Series Chipset with an RX 6000 Series GPU. The biggest difference here between the implementation of AMDs and NVIDIAs is that the NVIDIA support for ReBAR (Resizable BAR) is that it is supported on many more platforms.
In fact, NVIDIA has extended ReBAR support to even PCIe Gen 3.0 platforms by supporting Intel’s 10th Gen Core series CPUs with the 400 Series Chipsets already available. Interestingly, AMD’s CPUs support only includes the Zen 3 Ryzen 5000 series, which indicates that there is indeed more to it than just turning on a switch, but they even show support for the 400 series Chipset motherboards, as long as the BIOS has support.
Test setup
Test system
| Component | X570 |
|---|---|
| SVE | Ryzen 9 5900X (stock) |
| Memory | 32 GB Hyper X Predator DDR4 3600 |
| Motherboard | ASUS TUF Gaming X570 Plus WiFi |
| Storage | TeamGroup Cardea 1TB NVMe PCIe 4.0 |
| PSU | Cooler Master V1200 Platinum |
| Windows version | Latest version of windows during test |
| Hardware Accelerated GPU Planning | On if supported by GPU and driver. |
One of the interesting motivations with the addition of Resizable-BAR support by NVIDIA is that they are selective in which games get support and that it is done by the drivers. Why are you asking this? Well, for example in tests done by Hardware Unboxed, we’ve seen where AMD’s implementation of Smart Access Memory can sometimes lead to no performance benefit or performance degradation. Currently the list is rather limited, but it is expected that it will grow rapidly as we expand support to other cards. Games supported are;
- Assassin’s Creed Valhalla
- Battlefield V
- Borderlands 3
- Forza Horizon 4
- Rat 5
- Metro exit
- Red Dead Redemption 2
- Watch Dogs: Legion
RTX 3060 12GB Variable BAR 1440p Results
Closure
NVIDIA limiting game support at launch may have seemed odd, but it seems like they want to expand support for games that only benefit from the feature. In our results, we have seen a 4-11% increase in performance, something that is often not even achieved by a heavy overclock. This is a welcome result, and the fact that it will be updated by managers and whitelisted means that you do not have to worry about a game losing performance due to the size of the bar feature which is enabled in the BIOS.
The support for Resizable BAR on much cheaper charts will obviously be attractive, but at the moment it’s (even though it’s a bad time to say it) affordable price segment where things can really shake off technology like this. Combinations of Resizable BAR, Mesh Shaders, VRS and even DLSS can really change the expectations of the more midrange offerings. When the dust is away from misery for availability, I have a feeling that things like Smart Access Memory and Resizable BAR should be shown in performance comparisons because they are often too big to ignore for those who make purchases.
Breaking down performance in the space for graphics cards is becoming exponentially more complicated these days with all the amazing new features that come with all DX12 Ultimate GPUs, making it quite exciting as long as we can actually buy it.