What is Resizable BAR, and should you use it?

Back when Nvidia first started enabling Resizable BAR on their graphics cards in 2021, it didn’t take long for the promise of gloriously juiced-up game framerates – achieved with all the effort of flicking on a lightswitch – to be revealed as something only mildly helpful at best, and a crazy handful of nothing at worst. I ended the original version of this article by hoping aloud that ReBAR would blossom into something more impactful, and so since Nvidia, AMD, and Intel are all launching new GPU generations at the moment, I thought it’d be a good time to check in and see how it’s getting on.

If, however, you’re just joining us, you might have glazed over those first 102 words thinking: what is Resizable BAR, exactly?

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Resizable BAR explained

Before getting into how exactly Resizable BAR works, I want to be more upfront than the original post was that it’s far from an Nvidia-exclusive technology. While AMD calls it Smart Access Memory (SAM) instead, ReBAR works across CPUs and GPUs made by all three of the aforementioned manufacturers – which is just as well, as the process involves both of those key PC components working in tandem.

All gaming PCs produce an on-screen image by way of the CPU processing data – textures, shaders and the like – from the graphics card’s frame buffer. Usually the CPU can only access this buffer in 256MB read blocks, which obviously isn’t very much when modern GPUs regularly have 8GB of video memory or much, much more.

Resizable BAR (or SAM) essentially makes the entirety of the graphics frame buffer accessible to the CPU at once; where it could once sip, it now guzzles. The idea is that once textures, shaders and geometry are loading in faster, games should run faster with higher framerates.

Sounds like a sweet deal so far, though you will need to meet some hardware requirements. While any AMD Ryzen CPU and/or Intel Arc GPU will do, Intel chips should be 10th gen or newer, while the graphics card must be at least either a Radeon RX 6000 series or an Nvidia GeForce RTX 30 series (or newer, in both cases).

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Does it actually work, though?

When I first tested Resizable BAR on an RTX 3070, it didn’t really do much of anything. Some games ran a little faster, some a little slower, yet since the difference only ever amount to a tiny amount of frames-per-second – nowhere near enough for even a trained eye to spot the difference – it was all much of a muchness. Upscalers like DLSS were and still are much more effective at massaging performance, so say nothing of the various frame generation tools that have launched more recently.

Still, could several years of maturation, newer benchmark games, and a higher-tech RTX 4060 produce more tangible results? No, is the answer to that:

I’m not saying all games will perform identically with Resizable BAR on or off, but statistically speaking, it seems that’s a pretty damned likely outcome. Or, at least, it is if you’re using an Nvidia or AMD graphics card. If you’ve gone third-party-candidate and picked up an Intel Arc GPU, it’s a rather different story.

See, Arc GPUs are literally built differently to their more established Radeon and GeForce counterparts, with Intel making ReBAR’s buffer-opening machinations a more integral part of how their graphics cards operate. To the point where leaving ReBAR/SAM disabled while running an Arc GPU means you’re not just slowing it down, you’re tripping it up and beating it with dining table legs on the cobbles. Here’s the before-and-after with Intel’s latest Arc B580:

Indeed. Denying the Arc B580 access to Resizable BAR can cut its performance by almost half in certain games, and those can still be considered the lucky ones, as in F1 24 I couldn’t even get to the benchmark without the entire test PC blue screening.

You could argue that making it a downright necessity isn’t really in keeping with the spirit of Resizable BAR as a magic turbo button for improving framerates. But then, it’s still evidently not so great at doing that on Nvidia cards either.

So long as we’re tenuously stretching for positives, it’s also true that Resizable BAR won’t hurt performance on modern hardware. Thus, while it’s only truly a must-use feature for Intel GPUs, you shoudn’t worry much about its effects on GeForces and Radeons. A lot of gaming laptops and pre-built PCs have it switched on by default, and you don’t have to rush to disable it.

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How do I turn Resizable BAR on and off?

Let’s say that you do want to disable a pre-set ReBAR, or have just bought an Intel Arc card and need to make sure it’s enabled. Turning Resizable BAR on and off invariably requires a trip into the BIOS, so restart your PC and hit the Del or F12 keys as it’s booting up to enter it.

Some BIOS/UEFI layouts helpfully include a quick Resizable BAR toggle in their EZ mode screen, like here at the top of Asus’s design. If you can find this switch, use it to set ReBAR to your desired status, then restart your PC for the change to take effect.

If there’s no easy toggle, look within the BIOS’s advanced settings (most likely under a PCI submenu) for Resizable BAR/Resize BAR and Above 4G Encoding settings. Make sure both of these are enabled, then head for the Boot menu and disable the Compatibility Support Module (CSM) before saving and exiting. To turn off Resizable BAR later, you can just revert any of these changes back in the BIOS.

Be wary about messing with the CSM on systems with older storage, mind: if you have Windows installed in the old MBR format instead of the newer GPT, disabling the CSM will mean you can’t boot unless you either re-enable it or reinstall Windows using the GPT format.

You can check whether Resizable BAR is active through the Nvidia Control Panel. Click "System Information" in the bottom-left corner and you should find it listed among your GPU details. If marked "Yes", it will take effect in supported games, and if it’s marked "No", it’s currently disabled.

Likewise, Intel Arc owners can check that it’s enabled correctly via the Intel Graphics Software app. In the current version (as of January 2025), if you navigate to Settings > System and expand the Hardware Information section, you’ll see whether Resizable BAR is enabled near the top of the list.