NVIDIA RTX 30 Series Resizable BAR Technology Review

NVIDIA RTX 30 Series Resizable BAR Technology Review

What is Resizable BAR?

This is an old optional feature of the PCIe interface, which allows the processor to access all the memory of the video card at the same time, rather than in chunks of 256 MB. It was not included to maintain backward compatibility, but modern video cards come with so much VRAM (up to 24 GB), and games use such large files that it becomes more and more unprofitable to access memory piece by piece. Resizable BAR allows the processor to work with any necessary amount of video card memory, and not write it in chunks one at a time.

The technology was introduced by AMD, calling it Smart Access Memory (SAM) and with loud fanfare introducing it into Radeon 6000-series video cards and Ryzen 5000-series processors. A little later, Intel announced support for Resizable BAR in 10th and 11th generation processors, and in February, NVIDIA pulled up, adding it to laptops with GeForce RTX 30 series, desktop GeForce RTX 3060 video cards, and then all other cards. 30th series. There is nothing stopping us from adding the technology to the cards of the previous series, but so far there have been no announcements about this.

How do I enable Resizable BAR?

Unfortunately, Resizable BAR is still available only on the latest hardware – processors, motherboards and video cards of the past and this year. To enable the function, you need to update Windows 10 to version 20H2 or newer, update the video card driver to 465.89 WHQL dated March 30, 2021 or newer, update the BIOS of the motherboard and the VBIOS of the video card if you do not have an RTX 3060 in which the update is already installed.

After the update, you need to go into the BIOS and activate the Resizable BAR. For ASUS, for example, a button appears in the main menu, for other manufacturers this function can be hidden in the PCIe settings behind the Above 4G decoding setting, which must also be enabled.

equipment requirements

How to check if Resizable BAR is enabled?

Open NVIDIA Control Panel and click System Information in the lower left corner.

The EVGA Precision X1 software has a Re-BAR tab, which shows what still needs to be updated and if the technology is enabled.

Gaming performance

All games were tested in three resolutions 1920×1080, 2560×1440 and 3840×2160 at the maximum graphics preset. If the game supports ray tracing, then it was also enabled to increase the load on the video card. We are interested in the breaking point, when the video card operates at the peak of its capabilities and how the Resizable BAR can expand these capabilities. Or, as testing has shown, on the contrary, it can cut these opportunities.

• Assassin’s Creed Valhalla(2020) – Ultra High
• Control: Ultimate Edition(2019) – Ultra, RTX High, DLSS Q
• Cyberpunk 2077(2020) – High, RTX Psycho, DLSS Balance
• Death Stranding(2020) – High, DLSS Q
• Forza Horizon 4(2018) – Ultra
• Gears 5(2019) – Ultra
• Hitman 2(2018) – Ultra
• Horizon Zero Dawn(2020) – Ultra
• Metro Exodus(2019) – Very high, RTX ON
• Red Dead Redemption 2(2019) – Ultra
• A Total War Saga: Troy(2020) – Ultra
• Gears Tactics(2020) – Ultra

Test configuration

Average frame rate

As we already mentioned, Resizable BAR cannot magically increase the memory bus bandwidth, so lower-end cards will get less performance gain than older models. This is especially noticeable in Control, where on the RTX 3070 at 1080p the performance with reBAR drops noticeably (about 20 FPS), and on the contrary takes off by 30 FPS at 1440p. At 3080 there is almost no subsidence, at 3090 it turns into a small plus. The combination of NVIDIA GeForce RTX 3090 and AMD Ryzen 9 5900X gives the best results – up to 36% in Cyberpunk 2077. Newer, graphically intensive games generally get the biggest gains because they use a lot of large textures and models. High resolutions also consistently provide significant gains.

Rare events, 1%

Rare events are the minimum frame rate to which the game performance drops. Despite the fact that these are minimal results that only happen in 1% of the playing time, the performance of rare events shows how smoothly the game works in difficult situations, such as the height of a firefight. In many situations, the minimum 1% frame rate is even more important than the average frames per second.

The results for the 3070 and 3080 vary greatly, not only between games, but even between resolutions. Most likely, the point is in the damp motherboard BIOS for the new Intel Core i9-11900K processor, because the combination of Ryzen 9 5900X and RTX 3090 has much more stable results. New games like Assassin’s Creed Valhalla, Horizon: Zero Dawn, and Gears Tactics have seen significant increases in minimum frame rates, but Cyberpunk 2077’s most impressive results are up to 46%! On the other hand, in Metro Exodus, performance in rare events dropped slightly across all configurations.

Should I enable Resizable BAR?

If you have modern suitable hardware, it is definitely worth it. New hi-res high-tech games with large textures and models are getting a tangible boost. Most importantly, the Resizable BAR is likely to provide more and more performance gains in the future as developers begin to optimize games based on technology, and drivers and BIOS are likely to be improved. Now, at least, reBAR gives + 10-30 FPS in Cyberpunk 2077, both on average and in important 1% rare events. Spending 10 minutes will make the game noticeably smoother. A trifle, but nice!

Please note that we did not include programs for work like Photoshop, Blender, DaVinci Resolve, etc. in our testing, because they do not get any benefit from reBAR at all. Therefore, if you are only working at a computer, you may not even bother to turn on the technology. Although who knows, maybe in the future, working software will also start using the resizing of the memory register.

The introduction of the Resizable BAR is a very rare event in computing. One switch allows you to significantly speed up the video card. Often the difference is similar to the difference between two different cards, but the whole lineup has accelerated. We are still waiting for Microsoft to introduce DirectStorage technology in Windows 10, which will allow games to decompress game data on the fly at the power of video cards and directly into the memory of video cards, bypassing the processor and RAM, as the new PS5 and Xbox Series consoles do. How the two technologies will work together and whether PCIe 4.0 support will help them is still unknown, but the fact that the industry is giving out free upgrades definitely warms the heart.