Intel's support software says Resizable BAR is "required for optimal performance" with your Arc A-Series card. Or a build guide tells you to turn on Above 4G Decoding and Re-Size BAR Support, and you want to know what they do before you change firmware settings. Or NVIDIA Control Panel lists Resizable BAR as No and you wonder what you are missing. It is one feature with several names. Checking it takes a minute; turning it on takes longer if Windows was installed the old way.
What BAR is, and what resizing it changes
A PCI Express device such as a graphics card makes its memory reachable by the processor through a Base Address Register (BAR). Intel describes Resizable BAR as a PCIe capability that lets the device negotiate the size of that window. Without it, as Microsoft's driver documentation explains, a discrete GPU usually exposes only a small portion of its memory over the PCI bus, typically a 256 MB region kept for compatibility with 32-bit operating systems. With it, Windows renegotiates the BAR size after the firmware has initialised the machine and resizes it to its maximum, exposing the entire VRAM.
NVIDIA's launch explanation describes what that changes in a game. As you move through a world, textures, shaders and geometry are sent to VRAM through many small CPU-to-GPU transfers. With Resizable BAR the processor can access the whole frame buffer, so assets can be requested as needed and sent in full, and several transfers can run at once instead of queuing.
The names differ by vendor. AMD calls it Smart Access Memory and describes it as giving Ryzen processors full access to Radeon graphics memory; Intel notes that the firmware option may appear as Re-Size BAR, Smart Access Memory or Clever Access Memory.
What it needs
Every link in the chain has to support it, and several firmware settings have to line up. From Intel's and NVIDIA's instructions:
- Motherboard firmware that supports it. Intel says to use your board's latest firmware that supports Resizable BAR.
- UEFI boot, with CSM off. The Compatibility Support Module, also called Legacy mode, has to be disabled.
- Above 4G Decoding enabled. Intel notes that on some boards you have to enable it, save and restart before the Resizable BAR option appears at all.
- Resizable BAR itself, under whichever name your board uses. For both this and Above 4G Decoding, Intel's instruction is Enabled, or Auto if there is no Enabled option.
- Windows on a GPT disk, not MBR. NVIDIA's list says so directly, and Intel's Arc guide asks for UEFI boot mode and GPT partition style.
- A graphics card and driver that support it. For GeForce RTX 30 cards, NVIDIA lists a compatible CPU, motherboard and system firmware, an R465 or newer driver, and support in the card's own firmware (VBIOS). NVIDIA's VBIOS update tool covers its Founders Edition cards; other RTX 30 cards get theirs from the card's maker. For laptops, NVIDIA's advice is to check with the manufacturer.
To reach the firmware from Windows 11, Microsoft's route is Settings > System > Recovery, Restart now under Advanced startup, then Troubleshoot > Advanced options > UEFI Firmware Settings > Restart. If that option is not offered, use the key your motherboard's manual gives for entering setup at power-on.
How to check it is on
- NVIDIA: NVIDIA's instructions are to open NVIDIA Control Panel, click System Information at the bottom left and find Resizable BAR, which should read Yes. The Control Panel is now the legacy tool: NVIDIA retired it for Game Ready and Studio drivers with driver 610.47 in May 2026. An existing install stays unless you do a clean driver installation, and NVIDIA still offers it in the Microsoft Store; NVIDIA Control Panel settings explained covers the move to the NVIDIA app.
- Intel Arc: Intel says to use Intel Graphics Software or the Intel Driver & Support Assistant. The assistant shows the message "Resizable BAR is required for optimal performance with Intel Arc A-Series Graphics" when it finds Resizable BAR not present or not working, and Intel's listed causes are a motherboard that needs a firmware update or has no Resizable BAR support in its firmware.
- AMD: in the firmware, the option may itself be labelled Smart Access Memory, one of the names Intel lists. A driver installation can matter too: as of October 2026, AMD's Adrenalin 26.9.2 release notes list a known issue in which Smart Access Memory may become disabled after a driver installation on Windows 10 systems.
Why NVIDIA turns it on one game at a time
Turning Resizable BAR on in the firmware does not mean every game uses it. When NVIDIA added support in 2021, it reported that in its testing some titles benefited by a few percent, but that there were also titles that saw a decrease in performance. So NVIDIA said it would pre-test games and use game profiles to enable Resizable BAR only where it has a positive performance impact, adding titles through Game Ready driver updates. The list at launch had 17 games.
So Yes in System Information tells you the platform side is ready; whether a particular game uses it is NVIDIA's per-game decision. Forcing it on for games outside that list goes against what NVIDIA itself reported, that some titles ran slower with it. AMD words its own claim narrowly too, as a benefit "across select titles" rather than everywhere.
Intel Arc is the exception. Intel's Arc quick start guide says Resizable BAR must be enabled "for optimal performance in all applications" on both its A-Series and B-Series cards. On an Arc card, treat it as a requirement rather than an option.
If Windows is on an MBR disk
Resizable BAR needs UEFI boot, and both NVIDIA's and Intel's instructions ask for Windows on a GPT disk. Check first: in Disk Management, right-click the disk, choose Properties, open the Volumes tab and read Partition style. Or run Get-Disk | ft -Auto in PowerShell and read the Partition Style column.
If it says MBR, Microsoft's MBR2GPT tool converts the system disk to GPT without modifying or deleting data. It is already in Windows\System32, and from an elevated command prompt in Windows it runs with /allowFullOS:
mbr2gpt /validate /allowFullOS
mbr2gpt /convert /allowFullOSValidation checks the layout first, including at most three primary partitions and no extended or logical partitions. If any check fails, the conversion does not proceed.
Read this before converting. The tool itself warns that after a successful conversion "the disk can only be booted in GPT mode", and that the change cannot be undone. Make sure the PC supports UEFI first, and straight after converting, switch the firmware from Legacy/CSM to UEFI, because until you do Windows cannot boot properly. If BitLocker is on, suspend protection before converting; Microsoft says the existing protectors then have to be deleted and recreated to resume it. Back up anything you cannot afford to lose before you start.
After the conversion, in the firmware: CSM off, UEFI boot on, then Above 4G Decoding, then Resizable BAR. Secure Boot depends on the same UEFI switch, which is why Secure Boot and TPM 2.0 for anti-cheat starts from the same place.
What does not help
- Resizable BAR as extra memory. It changes how much of the card's memory the processor can reach at once, not how much memory the card has. If a game runs short, running out of VRAM is the page.
- Assuming a firmware update kept your settings. After any firmware update, go back in and check CSM, Above 4G Decoding and Resizable BAR. Treat it as a checklist step rather than an assumption either way.
- Expecting a number without measuring. NVIDIA's own testing found it helps some games and hurts others. The only figure that applies to your game is one you measured before and after; reading the benchmark covers how.
Related
- Clean Install for Stable 1% Lows
- Running out of VRAM
- Secure Boot and TPM 2.0 for anti-cheat
- NVIDIA Control Panel settings explained
- Reading the benchmark
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