Highly anticipated: Nvidia has finally started rolling out the resizable BAR support, starting with the RTX 3060 desktop and selected select laptops from the RTX 3000 series. Activating it may be a bit of a hassle, but it’s a free upgrade, so it gets a thumbs up.
The resizable BAR is a feature of the PCIe standard that allows a system’s CPU to view the entire GPU memory subsystem, instead of just a small 256 MB portion. Implementing the feature requires low-level support on the CPU, motherboard and GPU, which is like AMD, which designs all three, was the first to market a scalable BAR implementation called SAM (intelligent access memory).
In our tests, enabling SAM on an RX 6800 can improve the average frame rate for a game by up to 20% or impair it by up to 10%. In most titles, however, enabling the feature did almost nothing, which is reflected by the average improvement: only 3%.
Understandably, then, Nvidia is taking a different path. Your drivers will leave the resizable BAR disabled by default, and will only turn it on for titles where Nvidia has found that it improves performance. At the time of writing, there are 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, says Nvidia, the resizable BAR can improve performance “by a few percent, up to 10%.” At the end of March, when the rest of the RTX 3000 series receives support for a 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 is an advantage that is negated by the complexity of enabling the scalable BAR.
On laptops, the situation is good, but not very good: some laptops come with the resizable BAR enabled, others do not, and there is nothing you can do about it. Nvidia says to “check with each laptop manufacturer to find out if the resizable BAR is compatible with a specific model”.
Desktop compatibility is a 3D chess game. Enabling resizable BAR or, equally likely, discovering that your system does not support it, is a five step process. First, you need to make sure your CPU is compatible: all AMD 5000 series CPUs are, as are all 10th generation Intel processors, but only the next 11th generation i5, i7 and i9 series will be compatible. Simple enough …
Step two: check the motherboard chipset. AMD 500 series chipsets are compatible (although undesirable at the moment) and 400 series chipsets are compatible on motherboards that are also compatible with 5000 Ryzen series CPUs. The 500 series chipsets announced by Intel at the time are all compatible, as are all 400 series chipsets. Still with me?
Step three is more problematic: you will need to update the motherboard’s SBIOS, but you will have to hope for an update. According to Nvidia, “the following manufacturers are offering SBIOS updates for selected motherboards to enable the 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 on its own, but everyone else will need to download the update on your GPU manufacturer’s page.
And the bottom line: update your GPU drivers. After that, you can verify that the resizable bar is working correctly in the Nvidia Control Panel, under the System Information tab.