This important GPU feature is not as simple as you might think

Resizable Bar has been a feature on AMD and Nvidia graphics cards, along with Intel and AMD CPUs, for several years. You’ve probably heard of it if you follow the world of PC gaming. Since its introduction, ReBar has become one of the essential features that can be enabled on any gaming PC, along with memory overclocking profiles such as Intel XMP. It’s important that most modern motherboards come with the feature already enabled so you don’t have to think about it.

You’ll want to leave this feature enabled for general use, although it doesn’t provide performance improvements in every game. However, the further you dig into ReBar and its support, the more complicated it becomes. While you can enable the feature and forget about it, there are many features of ReBar that you should know about if you want to get maximum performance from your PC.

What is ReBar?

Nvidia

The name Resizable Bar doesn’t tell you anything about what the feature does. This is a feature of PCI Express, where you insert a graphics card, and it allows the graphics card to set the size of the BAR, or Base Address Register, which optimizes system resources. For PC gaming, this allows the CPU to access your graphics card’s full VRAM at once, which is expected to improve performance.

Without it, your CPU is only able to access 256 MB of your video memory at a time, and that’s a bit of a problem. Modern graphics cards like The RTX 4060 has a minimum of 8 GB of VRAM, while flagship devices like the RTX 4090 can be upgraded to 24 GB. ReBar allows full access to all that memory.

ReBar is the official name, but you’ll also see AMD’s Smart Access Memory (SAM). The same as ReBar, only branded if it uses an AMD GPU and AMD CPU. In theory, SAM and ReBar should be the same, but as I’ll discuss in a moment, that’s not entirely true.

So, it’s all in ReBar’s favor, right? This allows you to use all your memory at once, which will result in increased performance. It’s true, ReBar does improve performance in some games, but your mileage with ReBar will vary greatly depending on the hardware you have, the games you play, and whether you Actually has ReBar enabled.

When it works

I don’t want to retread with ReBar here. If you haven’t seen the tests done a few years ago when Nvidia enabled the feature, I’d direct you to Guru3D direction. On supported titles, you’ll typically see performance increases in the low single digits. The improvements are never huge, but enough that you’ll want to leave ReBar active.

This is also true in modern games. Testing at 1080p with an Nvidia RTX 4060 Ti and an AMD Ryzen 9 7950X, I noticed little change in performance on both Evil Residence 4 And Hogwarts Legacy. This shouldn’t work, and I’ll get to why shortly, but the results are repeatable.

ReBar performance on Nvidia GPUs.
Jacob Roach / Digital Trends

However, there are more games where you don’t notice the difference. You can see it at work F1 2022, where turning on ReBar had no effect whatsoever on performance, either with or without ray tracing active.

The problem with looking at benchmarks on just one system is that ReBar is highly dependent on the hardware you’re running on. A good example is the Intel Arc A770/A750. If you turn off ReBar with one of these graphics cards, you will see a huge drop in performance. There’s also SAM, which can show performance increases (or decreases) in games as opposed to ReBar on Nvidia GPUs (see TechPowerUp testing).

ReBAR results for Intel Arc GPUs.
Jacob Roach / Digital Trends

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

Nvidia warning

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

As mentioned in the last section, we should not see any performance improvements Evil Residence 4 And Hogwarts Legacy with ReBar on an Nvidia GPU. The reason is that Nvidia only enables ReBar on certain games via its drivers, and Hogwarts Legacy And Evil Residence 4 not on that very short list.

Further complicating the issue is that Nvidia hasn’t published a list of supported ReBar games since introducing the feature in 2021. Back then, there were 19 supported games, and since then, that’s the only official list we’ve seen. That’s true even if you check whether ReBar is enabled in the Nvidia Control Panel. This will show that the feature is active, 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 is publishing in 2021, and users are finding that out Nvidia Profile Inspector. This third-party tool essentially breaks the chain in the Nvidia Control Panel, showing you all the configuration options that are not normally available to users. Through this, user has found that Nvidia has added support for additional games over the past two years, incl Forza Horizon 5 and it Dead Space Remake. You can verify this yourself by downloading Nvidia Profile Inspector and checking the profiles for these games.

This tool also lets you force ReBar to be enabled by enabling it for games that are not technically supported. I did that in both Hogwarts Legacy And resident evil 4, and there’s actually a slight performance increase Hogwarts Legacy. On the other hand, there is a slight decrease in performance Evil Residence 4.

Nvidia performance with ReBar is forced through Nvidia Profile Inspector.
Jacob Roach / Digital Trends

This may seem like a difference — and honestly, it probably is — but forcing ReBar on unsupported games can have a detrimental impact on performance. In the The Last of Us Part One, for example, turning on ReBar in the BIOS has no effect whatsoever on performance. This isn’t a supported game, so ReBar doesn’t actually work on Nvidia GPUs. However, when you force it on in Nvidia Profile Inspector, there is a huge performance drop.

This may be a clue to why Nvidia hasn’t talked about ReBar much lately. This doesn’t seem to provide much benefit even on supported games, and on some unsupported titles, there may be a huge performance hit.

One size does not fit all

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

It’s a good idea to have ReBar enabled by default, but knowing the surrounding context is important. For AMD and Intel, you can leave ReBar active without any problems. For Nvidia, you should also leave it on while realizing that it doesn’t do anything in most of your games. Nvidia’s idea behind enabling this feature was initially to test individual games and only enable those that show a positive impact, so you don’t have to worry about whether you’re getting the best performance.

But that’s not all PC gamers. If you want to find those small performance improvements, there are games that benefit from forcing ReBar on via the Nvidia Profile Inspector as shown by Hogwarts Legacy. But be prepared for a lot of tinkering, because there are similar games The Last of Us Part One which shows a major performance drop.

You should already have ReBar enabled on your PC, but if not, be sure to read our guide how to activate Resizable Bar. You can quickly check whether the feature is enabled via the Nvidia Control Panel (click Information Systems) or Radeon Software if you have an AMD GPU.

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