Resizable BAR for Gaming: What It Does, How to Enable It and When It Matters

Resizable BAR is a PCIe feature that lets your CPU access the graphics card’s entire video memory at once instead of through a small 256 MB window. It usually adds a few percent to frame rates in supported games, occasionally more, and rarely costs anything. It matters most on newer GPUs and is close to essential on Intel Arc cards, but it needs a compatible CPU, motherboard BIOS and UEFI boot setup before it will turn on.

What Resizable BAR Actually Changes

A BAR, or base address register, is the region of address space through which the CPU reads and writes a PCIe device. For decades, graphics cards exposed only a 256 MB window of their video memory to the CPU, regardless of how much VRAM they had. When the CPU needed to send textures, geometry or other data to a card with 8 or 16 GB of VRAM, it had to do so in pieces through that small window, shuffling it along.

Resizable BAR is a standard PCIe feature that lets the window grow to match the full VRAM size. The CPU can then address all of the card’s memory directly, with fewer requests and less overhead. AMD markets its version as Smart Access Memory, while NVIDIA and Intel use the Resizable BAR name. They rely on the same underlying standard, and the motherboard setting may be labeled any of those names.

It does not increase your VRAM, raise clock speeds or change image quality. It reduces the cost of moving data between the CPU and the GPU, so it helps most in games that stream large amounts of assets during play.

Compatibility Requirements

Exact support varies by board and BIOS, so use the maker’s compatibility notes when a model sits at the edge of these lists.

Who Actually Benefits

Independent reviews from hardware outlets have generally found average gains in the low single-digit percent range, with a handful of games noticeably higher and some showing no change or a slight loss. Treat it as a free improvement, not a major upgrade.

One difference between vendors is how it is applied. AMD enables it broadly. NVIDIA’s driver uses a per-game list, enabling it where its testing showed a benefit and leaving it off elsewhere, so a game not on the list will not use it even when the feature is on.

How to Enable It

1. Check whether it is already on. Open GPU-Z and look for the Resizable BAR field, or in the NVIDIA Control Panel open System Information and look for the same line. Many new systems ship with it enabled, so there may be nothing to do.
2. Update the motherboard BIOS. Older BIOS versions often lack the setting entirely. Install the current version from the motherboard maker’s support page, following their instructions, since an interrupted flash can leave the board unusable.
3. Update the graphics firmware if the card maker requires it. Some first-generation RTX 30 cards need a VBIOS update from the manufacturer before the card reports support. Check the maker’s support page for your model.
4. Confirm you boot in UEFI with a GPT disk. Press the Windows key plus R, run msinfo32 and check that BIOS Mode says UEFI. If it says Legacy, the disk probably uses MBR and must be converted. Windows includes a tool called mbr2gpt for this, and you should back up important data first. This step must come before disabling CSM, otherwise Windows will not start.
5. Enter the BIOS and disable CSM. CSM emulates the old BIOS, and Resizable BAR needs the system to run in native UEFI. This is usually under the Boot menu.
6. Enable Above 4G Decoding. This allows devices to use address space above 4 GB, which a large BAR requires. Without it, the Resizable BAR option is hidden or has no effect.
7. Enable Re-Size BAR Support. It may be called Resizable BAR or Smart Access Memory, and usually appears on the same advanced or PCI subsystem page. Set it to Enabled or Auto, depending on what your BIOS offers.
8. Save, restart and verify. Check GPU-Z or the NVIDIA Control Panel again. If the field reads Enabled or Yes, it is working. If not, review the earlier steps in order.

Common Failures and Fixes

• The option is missing. Usually the BIOS is out of date, Above 4G Decoding is off or CSM is still on. Fix those three in that order.
• Windows does not boot after disabling CSM. The disk is still MBR. Re-enable CSM to boot, back up your files, convert to GPT with the Windows tool, and then disable CSM.
• No display after changing the setting. An older GPU without a UEFI-compatible firmware may fail to initialize. Clear the CMOS using the motherboard jumper or battery method, then use an integrated graphics output or a newer card.
• BIOS shows Enabled, but GPU-Z shows Disabled. The most common cause is that the GPU firmware is missing support, or the driver is outdated. Update both the driver and the card’s VBIOS.
• Frame rate drops in one game. A small number of titles run slightly slower with it on. NVIDIA’s per-game list helps avoid this. If you see a regression, you can turn the feature off in the BIOS and compare directly.
• System instability after enabling. Rare, but possible on early BIOS versions. Updating the BIOS again, or reverting to the previous setting, resolves it.

Should You Bother?

If your hardware supports it and the setting takes only a few minutes in the BIOS, turn it on. The cost is nothing and the potential gain is real, if modest. If enabling it means converting a disk, flashing firmware and altering boot configuration on an otherwise stable system, weigh that effort against a likely gain of a few percent. Exceptions are Intel Arc owners, who should treat it as a requirement, and anyone who finds the feature already enabled by default.

Frequently Asked Questions

Does Resizable BAR increase FPS?

Usually by a small amount, often a few percent on average. Some games gain more, a few see no change, and a small number run slightly slower. The effect is clearest when the CPU is a larger part of the frame time.

Is Resizable BAR the same as Smart Access Memory?

They are the same underlying PCIe feature. Smart Access Memory is AMD’s marketing name for it, and the BIOS setting may use either name.

Is it safe to leave Resizable BAR on all the time?

Yes. It is a standard hardware feature, and it does not harm the GPU or the CPU. If a specific game behaves badly, you can disable it and compare, though most users never need to.

Why can’t I find the option in my BIOS?

Typically the BIOS is too old, or Above 4G Decoding and CSM are not set correctly. Update the BIOS, enable Above 4G Decoding and disable CSM, then look again in the advanced or PCI settings.

Does Resizable BAR work with older graphics cards?

Generally not. Support starts with the RTX 30 and RX 6000 generations, though some earlier cards received firmware updates. Check the card maker’s support page for your exact model.