This essential GPU feature isn’t as simple as you think

Resizable bars have been a feature on Intel and AMD CPUs, as well as AMD and Nvidia graphics cards, for a few years. If you keep up with the world of PC gaming, you’ve probably heard about it. Since its introduction, ReBar has become one of the essential features to enable on any gaming PC, along with memory overclocking profiles like Intel XMP. This is so essential that most modern motherboards come with the feature already enabled so you don’t have to think about it.

You should keep this feature on for general use, even if it doesn’t boost performance in every game. However, the more you delve into ReBar and its support, the more complex it becomes. Even if you can turn on this feature and forget about it, there are a lot of quirks with ReBar that you should know about if you want to get peak performance from your PC.

What is rebar?

An illustration of Nvidia's resizable bar.
NVIDIA

The name Resizable Bar doesn’t really tell you anything about what this feature does. This is a feature of PCI Express, where you slot in your graphics card, and it allows the graphics card to set a BAR, or base address register, size that optimizes system resources. For PC gaming, this allows the CPU to access your graphics card’s full VRAM at once, increasing performance.

Without it, your CPU can only access a 256MB portion of your video memory at a time, and that’s a bit of a problem. Modern graphics cards like the RTX 4060 have at least 8GB of VRAM, while flagships like the RTX 4090 can scale up to 24GB. ReBar allows full access to all that memory.

ReBar is the official name, but you’ll also see AMD’s Smart Access Memory (SAM). It’s the same thing as ReBar, just branded for if you use an AMD GPU and AMD CPU. In theory, SAM and ReBar should be the same, but as I’ll explain shortly, that’s not actually the case.

So, it’s all upside for ReBar, right? This allows you to use all your memory at once, which should increase performance. In fact, ReBar improves performance in some games, but your mileage with it depends on the hardware you have, the game you’re playing, and if you In fact ReBar is enabled.

when it works

I don’t want to repopulate the field with ReBar here. If you haven’t seen the testing that was conducted a few years ago when Nvidia enabled this feature, I would point you to Guru3D. In supported titles, you’ll typically see performance increases in the low single digits. The boost is never huge, but it’s enough that you’ll want to keep ReBar on.

This is true in modern games. When testing at 1080p with Nvidia’s RTX 4060 Ti and the AMD Ryzen 9 7950X, I saw minor changes in performance across both resident Evil 4 And Hogwarts Legacy. This shouldn’t work, and I’ll explain why shortly, but the results were repeatable.

Performance of Rebar on Nvidia GPUs.
Jacob Roach/

However, the number of games where you won’t notice any difference is far greater. you can see it at work f1 2022, Where turning on rebar did nothing to the performance, both with and without ray tracing.

However, the problem with viewing benchmarks on just one system is that ReBar is highly dependent on the hardware you’re running it on. A great example of this is Intel’s Arch A770/A750. If you turn off ReBar from one of these graphics cards, you will see a massive performance loss. It also has SAM, which may show performance improvements (or losses) in games running against Rebar on Nvidia GPUs (see TechPowerUp’s testing).

ReBAR results for Intel's Arc GPUs.
Jacob Roach/

For Intel and AMD systems, ReBar is a solid feature that sometimes provides minor performance lifts. However, the situation with Nvidia is much more complicated.

nvidia warning

Logo on the RTX 4060 Ti graphics card.
Jacob Roach/

As mentioned in the previous section, we should not see a performance increase resident Evil 4 And Hogwarts Legacy With Rebar on Nvidia GPU. This is because Nvidia only enables rebar on certain games through its driver, and Hogwarts Legacy And resident Evil 4 Not on that very short list.

What makes the issue more complicated is that Nvidia has not published any list of supported Rebar games since it introduced the feature in 2021. At the time, 19 games were supported, and since then, this is the only official list we’ve ever seen. This is true even if you check that ReBar is turned on in the Nvidia Control Panel. This will show that the feature is on, even if it is blocked by the Nvidia driver in most of your games.

Nvidia Control Panel Options.
digital trends

However, there are more supported games than Nvidia published in 2021, and users know through the Nvidia Profile Inspector. This third-party tool basically breaks the chains of the Nvidia Control Panel, showing you all the configuration options that are not usually available to users. Through this, users learned that Nvidia has added support for additional games in the last two years forza horizon 5 And this Dead Space Remake. You can verify this yourself by downloading the Nvidia Profile Inspector and checking the profiles for these games.

This tool also allows you to force ReBar by enabling it for games that are not technically supported. I did this in both Hogwarts Legacy And resident Evil 4, And there was actually a slight boost in performance Hogwarts Legacy. On the other hand, there was a slight loss in performance resident Evil 4.

Forced Nvidia performance with Rebar through the Nvidia Profile Inspector.
Jacob Roach/

This may seem like a mere variation – and in fairness, it might be – but forcing ReBar in games that aren’t supported can have some devastating performance effects. In The last of us part one, For example, turning on ReBar in the BIOS had no effect on performance. This is not a supported game, so ReBar is not actually working on Nvidia GPUs. However, when you apply it in the Nvidia Profile Inspector, there is a huge drop in performance.

This is probably indicative of why Nvidia doesn’t talk much about Rebar these days. Even in supported games it doesn’t provide much of a benefit, and in some unsupported titles, there can be a massive performance loss.

One size does not fit all

Two AMD Radeon RX 7000 graphics cards on a pink surface.
Jacob Roach/

It makes sense to have ReBar on by default, but it’s important to know the context around it. For AMD and Intel, you can safely keep ReBar running without any problems. As for Nvidia, you should keep it on even if you recognize that it’s doing nothing in most of your games. Nvidia’s idea behind turning on this feature was basically to test individual games and only enable the games that show a positive effect, so you don’t have to worry about whether you’re getting the best performance. Used to be.

But it’s not for all PC gamers. If you want to find those small performance improvements, there are games that benefit from forcing the rebar through the Nvidia Profile Inspector as shown Hogwarts Legacy. However, be prepared for a lot of fiddling, as such games also the last of us part one This represents a huge performance loss.

You should already have ReBar enabled on your PC, but if you don’t, be sure to check out our guide on how to enable Resizable Bar. You can quickly check whether the feature is enabled via the Nvidia Control Panel (click). system information) or Radeon Software if you have an AMD GPU.






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