How to Enable Resizable BAR and Above 4G Decoding in BIOS

Resizable BAR (called Smart Access Memory on AMD platforms) lets your CPU address the graphics card’s full video memory at once instead of through a small window. To turn it on, you enable Above 4G Decoding and Re-Size BAR Support in your motherboard’s UEFI setup, with CSM switched off and Windows booting in UEFI mode from a GPT disk. The whole job takes about 15 to 30 minutes, including a restart or two. It applies to Windows 11 gaming desktops with a recent GeForce RTX, Radeon RX or Intel Arc card and a compatible CPU and board.

Quick Answer

• Confirm Windows is in UEFI mode on a GPT disk: press Windows + R, run msinfo32, and look for BIOS Mode: UEFI.
• Update the motherboard BIOS and the graphics driver to current releases.
• In UEFI setup, set CSM to Disabled, Above 4G Decoding to Enabled, then Re-Size BAR Support to Enabled or Auto. Save and exit.
• Verify in NVIDIA Control Panel, AMD Software, Intel’s driver tools or GPU-Z that Resizable BAR reads Yes or Enabled.

Before You Start

This change touches firmware settings, so a few minutes of preparation prevents most problems.

• Check your hardware generation. NVIDIA documents Resizable BAR support for GeForce RTX 30-series cards and newer, AMD documents Smart Access Memory for Radeon RX 6000-series and newer paired with supported Ryzen processors, and Intel treats Resizable BAR as important for Arc cards. Older graphics cards generally do not offer it, even if your board shows the option.
• Check your CPU and board. Many Intel 10th-generation and newer systems and AMD Ryzen 3000 and newer systems with 400-series or newer chipsets can do it, but only after a BIOS update from the board maker. Laptops usually expose no switch at all; the manufacturer decides.
• Disabling CSM can stop Windows from booting. If Windows was installed in legacy (MBR) mode, turning CSM off will leave the PC unable to find its system disk. Confirm UEFI and GPT first (Method 1). If the PC does fail to boot, re-entering setup and turning CSM back on restores the old behavior.
• Record your current settings. Take a phone photo of any screen you change, especially boot mode, XMP or EXPO memory profiles and fan curves, because a BIOS update can reset them.
• BIOS updates carry risk. A power cut during flashing can leave a board unusable. Use a stable power source, follow the board maker’s instructions exactly, and do not update if the PC is already working with Resizable BAR on.
• Suspend BitLocker if you use it. Firmware changes can trigger a BitLocker recovery prompt on some systems. Know where your recovery key is stored before you continue.

Method 1: Confirm Windows Uses UEFI and GPT

Resizable BAR needs a pure UEFI boot path. NVIDIA also states that the boot drive must use the GPT partition style for the feature to work, so this check comes first.

1. Press Windows + R, type msinfo32 and press Enter.
2. In System Summary, read the BIOS Mode line. You want UEFI. If it says Legacy, stop here and convert the disk before touching CSM.
3. Right-click Start, choose Disk Management, right-click your system disk’s label on the left (for example Disk 0), choose Properties, open the Volumes tab and check that Partition style reads GUID Partition Table (GPT).
4. If the disk is MBR, open an elevated Command Prompt and run mbr2gpt /validate /disk:0 /allowFullOS. When validation passes, Microsoft’s tool can convert the system disk without deleting data using mbr2gpt /convert /disk:0 /allowFullOS. Back up first, because the conversion cannot be reversed, and switch the firmware from Legacy to UEFI right after the conversion.

Why it works: with CSM off, the firmware hands off to Windows only through UEFI, which is what allows the graphics card to map its full memory above the 4 GB address line.

Method 2: Change the BIOS Settings in the Right Order

Order matters because the Re-Size BAR option often stays hidden or grayed out until Above 4G Decoding is on.

1. Open UEFI setup. From Windows, go to Settings > System > Recovery, select Restart now next to Advanced startup, then choose Troubleshoot > Advanced options > UEFI Firmware Settings > Restart. You can also tap the Delete or F2 key at power-on.
2. Switch to the advanced view if the board opens in a simple mode (F7 on many ASUS boards).
3. Set CSM (also called Launch CSM or CSM Support, usually under Boot) to Disabled.
4. Set Above 4G Decoding (sometimes Above 4G memory or 4G Decoding) to Enabled.
5. Set Re-Size BAR Support to Enabled, or Auto if Enabled is not offered. If the option still is not visible, save with F10, re-enter setup and look again.
6. Press F10, confirm, and let Windows start. You should reach the desktop normally; a black screen or a repeating boot loop points to a mode mismatch covered below.

Menu names differ by vendor. Use the table as a starting point, then trust what your own screens show.

Method 3: Verify It Is Actually Active

Seeing the option enabled in BIOS does not prove the driver is using it, so check from Windows.

1. NVIDIA: open NVIDIA Control Panel, choose Help > System Information (or the System Information link at the lower left in older builds) and find the Resizable BAR line. It should read Yes.
2. AMD: open AMD Software: Adrenalin Edition and check the status area on the Home page, or go to Performance > Tuning where the Resizable BAR (Smart Access Memory) state is shown. Treat Unsupported as a sign that a BIOS or boot-mode requirement is missing.
3. Intel Arc: use the Intel Driver and Support Assistant or the Arc driver software, then cross-check with GPU-Z. Intel notes that its Arc Control app can wrongly show Resizable BAR as not supported even when it is on.
4. Any card: open GPU-Z, switch to the Advanced tab, open the dropdown that lists PCIe Resizable BAR, and read the status it reports. Both hardware support and enabled status should say Yes.

Why it works: the driver reads the BAR size the firmware exposed. If the firmware only offers the legacy 256 MB window, the driver reports the feature as off.

If It Did Not Work

• The Re-Size BAR option is missing. Update the BIOS first, then enable Above 4G Decoding, save, restart and re-enter setup. Some boards reveal the second option only after the first is saved.
• The PC shows “no boot device” or loops after saving. You likely disabled CSM on a legacy MBR install. Re-enter setup with the Delete or F2 key, set CSM back to Enabled, boot Windows, then do Method 1 properly.
• NVIDIA still says No. Re-check CSM, GPT and UEFI mode. If those are right, the graphics card’s firmware may need an update from the card maker; NVIDIA publishes a Resizable BAR firmware update tool for certain older RTX 30-series cards.
• AMD shows Unsupported. Confirm your CPU generation is supported, install the latest chipset driver, and confirm the BIOS carries a recent AGESA update.
• Black screen at startup after enabling Above 4G. Clear the CMOS using the board’s jumper or button (see the board manual), then repeat the steps and leave Re-Size BAR on Auto.
• Instability or crashes after the change. Revert the Re-Size BAR setting to Disabled, update the graphics driver with a clean install, and look for related entries in Event Viewer under Windows Logs > System.

Common Questions

Will it raise my frame rate?

Gains vary by game and hardware. NVIDIA says some titles benefit while others may not, and it evaluates games individually before turning the feature on for them in its driver. Treat Resizable BAR as a low-risk setting worth enabling on supported hardware, not a guaranteed upgrade, and judge it by how your own games feel.

Is Resizable BAR the same as Smart Access Memory?

They describe the same PCI Express capability. AMD markets its implementation as Smart Access Memory and ASRock uses the name Clever Access Memory, while the PCI standard calls it Resizable BAR. The BIOS option is usually labeled Re-Size BAR Support.

Do I need Above 4G Decoding for it?

Yes. Resizable BAR cannot map more than the legacy window without it, which is why the option normally has to be enabled first. Some firmware labels it Above 4G memory or 4G decoding instead.

Can I leave Resizable BAR on all the time?

For most people, yes. It is a standard hardware feature, and drivers decide per game whether to use it. If a particular game misbehaves, you can turn the setting off in BIOS to compare, then switch it back.

Does it work on a laptop?

Sometimes. Laptop makers decide whether the feature is available and often hide the setting entirely. Check the manufacturer’s support page for a BIOS update rather than hunting for a menu that does not exist.

Will turning off CSM affect my other drives?

It only changes how the firmware starts the PC. Secondary data drives are unaffected, but a legacy-mode system disk will stop booting, which is why the GPT check comes first.

Update History

• October 14, 2026 – Initial publication; steps checked against Windows 11 24H2/25H2 and current driver releases.
• Menus can differ slightly by Windows build, BIOS vendor and driver version; check your own screens against the steps.

Sources

• NVIDIA GeForce support and news pages on Resizable BAR requirements and verification
• AMD support documentation for Smart Access Memory and AMD Software: Adrenalin Edition
• Intel support articles on Arc graphics and Resizable BAR
• Microsoft Learn documentation for MBR2GPT and Windows recovery options
• Motherboard vendor guides from ASUS, MSI and Gigabyte