How to Enable Resizable Bar Bios: Step-by-Step

Optimizing your home office workstation or gaming setup is about more than just routing cables and choosing an ergonomic chair. To squeeze every ounce of performance out of your hardware, you must dive into your system’s firmware. Enabling Resizable BAR (Base Address Register) is one of the most effective, free performance upgrades available for modern PCs, allowing your processor to access the entire graphics card frame buffer at once rather than in small, 256-megabyte chunks.

However, modifying your system BIOS is not without risk. If done incorrectly, you can easily end up with a black screen, an operating system that refuses to boot, or a system stuck in an infinite boot loop. This happens most frequently when users toggle settings without converting their partition style from older legacy formats to modern standards. Fortunately, with a methodical approach, you can safely unlock this feature and enjoy a smoother computing experience.

What You Need

Before entering your system BIOS, verify that your hardware and software environment support this technology. Below is a checklist of the components required to enable Resizable BAR successfully.

Step-by-Step

Follow these steps carefully to ensure your system transition is seamless. Rushing through BIOS adjustments can result in boot errors that require clearing your motherboard’s CMOS.

Step 1: Verify GPT Partition Style (Time Estimate: 5 Minutes)

Resizable BAR requires your system to boot in native UEFI mode, which is incompatible with older MBR partition schemes. To check this in Windows, right-click the Start button and select “Disk Management.” Right-click your primary boot drive (usually Disk 0), select “Properties,” and navigate to the “Volumes” tab. Look at “Partition style.” If it says “GUID Partition Table (GPT),” you are ready to proceed. If it says “Master Boot Record (MBR),” you must convert the drive to GPT before turning off Legacy boot support in your BIOS, otherwise your PC will fail to boot into Windows.

Step 2: Update Motherboard BIOS and GPU Drivers (Time Estimate: 15 Minutes)

Ensure you are running the latest graphics drivers from NVIDIA or AMD. Next, visit your motherboard manufacturer’s support page, locate your specific motherboard model, and download the latest BIOS version. Copy the BIOS file to a FAT32-formatted USB flash drive. Restart your computer, enter the BIOS utility (usually by tapping the Delete or F2 key), and use the built-in flashing utility (such as ASUS EZ Flash, MSI M-Flash, or Gigabyte Q-Flash) to update your motherboard firmware. Ensure your system remains powered on throughout this process.

Step 3: Enter the Motherboard BIOS/UEFI (Time Estimate: 3 Minutes)

Reboot your PC. As soon as the screen lights up, repeatedly tap the designated BIOS key (typically Delete, F2, or F12 depending on your motherboard brand). If your system boots too quickly to register the keystroke, hold down the Shift key while clicking “Restart” in the Windows Start menu. This will bring you to the Advanced Startup menu. Navigate to Troubleshoot > Advanced Options > UEFI Firmware Settings, and click Restart to boot directly into the BIOS.

Step 4: Disable CSM (Compatibility Support Module) (Time Estimate: 2 Minutes)

Once inside the BIOS interface, switch to “Advanced Mode” (usually by pressing F7). Locate the “Boot” or “Security” tab. Find the setting labeled “CSM” or “Compatibility Support Module” and set it to “Disabled.” Disabling CSM forces the motherboard to boot exclusively in UEFI mode, which is a mandatory prerequisite for enabling Resizable BAR.

Step 5: Enable Above 4G Decoding and Re-Size BAR Support (Time Estimate: 3 Minutes)

Navigate to the “Advanced” tab, then look for a sub-menu labeled “PCI Subsystem Settings,” “PCIe Configuration,” or “IO Ports.” Within this menu, locate two specific settings:

• Above 4G Decoding: Set this to “Enabled.”
• Re-Size BAR Support: Once Above 4G Decoding is enabled, this option will become toggleable. Set it to “Enabled” or “Auto.”

If you are using an AMD motherboard, these settings might be labeled as “Smart Access Memory” (SAM) or “Clever Access Memory” depending on the brand, but the underlying technology remains the same.

Step 6: Save Settings, Reboot, and Verify (Time Estimate: 5 Minutes)

Navigate to the “Save & Exit” tab, select “Save Changes and Reset,” and confirm. Your computer will reboot into Windows. To verify that the feature is functioning, right-click your desktop and open the NVIDIA Control Panel or AMD Software. In the NVIDIA Control Panel, click “System Information” in the bottom-left corner. Look through the list of details for “Resizable BAR”; it should now say “Yes.” For AMD users, look for “AMD Smart Access Memory” in the Performance tab to confirm it is enabled.

Mistakes to Avoid

• Forgetting to Disable CSM: If CSM is left enabled, the Resizable BAR option may remain grayed out or fail to function after booting into Windows.
• Ignoring Partition Styles: Attempting to disable CSM and enable UEFI boot on an MBR-partitioned drive will prevent Windows from booting, forcing you to go back into the BIOS to re-enable CSM.
• Updating BIOS During Unstable Weather: A power outage during a BIOS flash can permanently ruin a motherboard. Always use an uninterruptible power supply (UPS) if you live in an area prone to power fluctuations.
• Neglecting GPU Firmware Updates: Early RTX 30-series graphics cards (like the RTX 3080 10GB) require a secondary GPU firmware (VBIOS) update in addition to the motherboard BIOS update to support Resizable BAR.

How Often

Enabling Resizable BAR is a one-time configuration process. Once enabled, it will remain active indefinitely. However, you should re-verify its status after performing a motherboard BIOS update, as updating firmware typically resets all BIOS settings to their factory defaults. Additionally, when upgrading your graphics card or processor to newer hardware in 2026 or beyond, double-check that the setting remains active in your system configuration to maintain optimal performance.

When to Call a Pro or Replace

Most home users can successfully enable Resizable BAR on their own. However, if your computer fails to POST (Power On Self Test) after changing these settings, and clearing the CMOS (by removing the coin-sized CR2032 battery from the motherboard for 5 minutes) does not restore functionality, you may need to consult a professional computer technician.

If your current motherboard, processor, or graphics card does not support Resizable BAR, it might be time to plan an upgrade. Upgrading to a compatible motherboard (typically ranging from $100 to $250) and a modern power supply (650W to 850W, costing $80 to $150) will not only unlock this feature but also prepare your home computing setup for the heavier software and gaming demands of the future.

FAQ

Does Resizable BAR improve performance in every game?

No, the performance impact varies by title. In some modern, graphics-heavy games, you can see performance improvements of 5% to 15%. However, in older games or poorly optimized titles, it may have a negligible impact or, in rare cases, slightly decrease performance. Both NVIDIA and AMD use driver profiles to automatically disable the feature on games where it does not provide a benefit.

Can I enable Resizable BAR on an older GTX 10-series or 20-series card?

Officially, NVIDIA only supports Resizable BAR on RTX 30-series and 40-series graphics cards. Older architectures, such as the GTX 10-series (Pascal) and RTX 20-series (Turing), do not have the hardware-level capabilities required to utilize this feature, even if your motherboard supports it.

What should I do if my PC boots to a black screen after enabling it?

If your PC boots to a black screen, it is likely because CSM was disabled while your boot drive was still formatted as MBR. To fix this, turn off your PC, unplug the power cable, open the case, and remove the CMOS battery for 5 minutes to reset the BIOS settings to default. Once your PC boots back into Windows, convert your drive to GPT before trying again.

Is Resizable BAR safe for my hardware?

Yes, Resizable BAR is completely safe. It is an industry-standard PCI Express specification feature that does not overclock your hardware or increase power consumption beyond normal limits. It simply optimizes how data is shared between your CPU and GPU.