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Highly anticipated: Nvidia has finally begun rolling out Resizable BAR support, beginning with the desktop RTX 3060 and a select few RTX 3000-series equipped laptops. Enabling it can be a bit of a hassle, but it’s a free upgrade, so it gets a thumbs up.
Resizable BAR is a feature of the PCIe standard that enables a system’s CPU to see the entirety of the GPU’s memory subsystem, instead of just a small 256 MB portion. Implementing the feature requires low-level support in the CPU, motherboard, and GPU, which is how AMD, who designs all three, was the first to market with a Resizable BAR implementation called SAM (smart access memory).
In our testing, enabling SAM on an RX 6800 could improve a game’s average frame rate by up to 20%, or harm it by up to 10%. In most titles, though, enabling the feature did almost nothing, which is reflected by the average improvement: just 3%.
Understandably, then, Nvidia is taking a different route. Their drivers will leave the Resizable BAR disabled by default, and only switch it on in titles where Nvidia’s found that it improves performance. As of writing, that’s eight titles:
- Assassin’s Creed Valhalla
- Battlefield V
- Borderlands 3
- Forza Horizon 4
- Gears 5
- Metro Exodus
- Red Dead Redemption 2
- Watch Dogs: Legion
In these games, Nvidia says, Resizable BAR can improve performance "from a few percent, up to 10%." In late March, when the rest of the RTX 3000-series receives support for Resizable BAR, more games will be added to the list. Nvidia’s selective approach is undoubtedly a good idea (if done right) but unfortunately, it’s an advantage that’s negated by the complexity of enabling the Resizable BAR.
In laptops, the situation is okay but not great: some laptops will come with the Resizable BAR enabled, some won’t, and there’s nothing you can do about it. Nvidia says to "check with each laptop manufacturer to discover if Resizable BAR is supported on a particular model."
Desktop compatibility is a game of 3D chess. Enabling Resizable BAR, or, equally likely, discovering that your system doesn’t support it, is a five-step process. First, you’ll need to check if your CPU is compatible: all AMD 5000-series CPUs are, as are all 10th-gen Intel processors, but only the i5, i7, and i9 series from the upcoming 11th-gen will have compatibility. Simple enough...
Step two: check your motherboard’s chipset. AMD 500-series chipsets are compatible (if undesirable, at the moment) and the 400-series chipsets are compatible on motherboards that are also compatible with Ryzen 5000-series CPUs. The 500-series chipsets Intel’s announced as of writing are all compatible, and so are all their 400-series chipsets. Still with me?
Step three is more troublesome: you’ll need to update your motherboard’s SBIOS, but you'll just have to hope that an update exists. According to Nvidia, "the following manufacturers are offering SBIOS updates for select motherboards to enable Resizable BAR with GeForce RTX 30 series desktop graphics cards: Asus, Asrock, Colorful, EVGA, Gigabyte, and MSI."
Fourth, you’ll need to update your GPU’s VBIOS, unless you’re one of the lucky few with a new RTX 3060. For Founder’s Edition owners, Nvidia will provide the update themselves, but everyone else will need to download the update from their GPU manufacturer’s page.
And the home stretch: update your GPU drivers. Afterward, you can check if the Resizable BAR is working correctly in the Nvidia Control Panel, inside the System Information tab.