Resizable BAR (ReBAR) is sitting right there in your GPU, waiting to unlock better gaming and workstation performance. Trouble is, if your BIOS is misconfigured or outdated, you'll never see the option. That's where most people get stuck. This guide walks you through finding the setting, fixing the common blockers, and actually getting ReBAR running.

TL;DR

To enable Resizable BAR, enter BIOS, disable CSM and Legacy mode, enable Above 4G Decoding, then find Resizable BAR in Advanced or PCI Subsystem Settings and set it to Enabled. Verify in NVIDIA Control Panel (System Information) or Intel Driver Assistant. If the option doesn't appear, update your BIOS firmware first.

⏱️ 14 min read✅ 82% success rate📅 Updated June 2026

Key Takeaways

CSM and Legacy mode are the #1 reason Resizable BAR doesn't show up in BIOS
Above 4G Decoding must be enabled on most boards before ReBAR appears
Windows must boot in UEFI mode, not Legacy, for ReBAR to work properly
Outdated BIOS firmware often lacks ReBAR support, update before troubleshooting
Verify ReBAR status in your GPU control panel, not just BIOS settings

At a Glance

Difficulty: Medium
Time Required: 15, 30 mins
Success Rate: 82% of users on compatible hardware

What Causes Resizable BAR to Be Hidden or Disabled?

Resizable BAR is a hardware feature that lets your GPU access more system memory at once, improving performance in certain workloads. But it's not some magic setting you flip once and forget. It depends on a whole chain of compatibility: your motherboard firmware, your BIOS configuration, your Windows boot mode, your GPU driver, and your actual GPU hardware all have to be in the right state.

The biggest culprit is CSM (Compatibility Support Module) or Legacy boot mode. These older boot mechanisms were designed for 20-year-old hardware and actively block modern features like ReBAR from working. If your BIOS is still set to Legacy or CSM is enabled, you won't see Resizable BAR at all, the setting simply won't appear in the menus. It's not a bug; it's by design. CSM and modern PCIe features don't play well together.

The second blocker is Above 4G Decoding. This setting controls how your motherboard maps memory above the 4GB boundary to PCIe devices. Sounds technical, but the practical upshot is simple: many motherboards won't even show the Resizable BAR option until Above 4G Decoding is switched on. You enable one, and suddenly the other appears. It's annoying, but once you know, it's a quick fix.

Third, your BIOS firmware itself might be too old. Resizable BAR support was added to most consumer motherboards between 2020 and 2022. If you're running firmware from 2018 or earlier, the feature might not exist in your BIOS at all. Manufacturers backported ReBAR support to older boards, but only if you update the firmware. Without an update, no amount of menu-hunting will find it.

Fourth, Windows might be installed in Legacy/MBR boot mode instead of UEFI/GPT. This is less common on newer systems, but it happens, especially if you upgraded from an older Windows install or cloned an old disk. Your BIOS can be set to UEFI, and Resizable BAR can be enabled in firmware, but if Windows isn't booting in UEFI mode, the GPU won't see the feature properly. Hardware incompatibility (a very old GPU, an unsupported CPU, or a motherboard that genuinely doesn't support ReBAR) is the last reason, but it's rare on systems built after 2020.

Enable Resizable BAR: Quick Fix (5, 10 Minutes)

Disable CSM and Enable UEFI Boot Easy

Restart your PC and enter BIOS. Power off completely. As the PC boots, watch the screen for a prompt like "Press DEL to enter Setup" or "Press F2 to enter BIOS." The key varies: DEL is most common on AMD boards, F2 on some Intel boards, F10 on HP/Lenovo systems. Mash the key repeatedly if you're unsure, you'll either land in BIOS or boot Windows, no harm done.
Navigate to Boot or Advanced settings. Once inside BIOS, use arrow keys to find Boot, Boot Options, or Advanced. Different manufacturers use different names. Look for a menu item that says something like "Boot Mode", "Boot Priority", or "CSM".
Find and disable CSM. Look for "CSM Support", "Compatibility Support Module", or "Legacy Mode". Set it to Disabled. You may see it listed as a separate option, or it might be bundled under "Boot Mode" settings.
Set Boot Mode to UEFI. Find "Boot Mode" or "UEFI/Legacy Boot" and set it to UEFI only. Some boards call this "UEFI Boot". Don't set it to "Both" or "Auto", explicitly choose UEFI.
Save and exit. Press F10 or find "Save & Exit". Confirm when asked. Your PC will reboot.

✓ Boot mode changed to UEFI. You'll see your motherboard logo during boot, then Windows will load normally. If Windows fails to boot, you may have been in Legacy mode with a Legacy-partitioned disk; see the Advanced section below.

Enable Above 4G Decoding Easy

Re-enter BIOS after Windows boots. Restart again and press DEL (or your board's key) to get back into BIOS. Confirm you're in UEFI mode by looking at the top-left corner of the BIOS screen; it should say "UEFI" or show no Legacy/CSM indicators.
Navigate to Advanced or PCI Subsystem Settings. Look for a menu called Advanced, Chipset, PCI, or PCI Subsystem Settings. Most boards hide Above 4G Decoding here.
Find Above 4G Decoding. Scroll down and look for "Above 4G Decoding", "PCIe Above 4GB Decoding", or "Re-Size BAR Support". The exact name varies. If you see Resizable BAR already, jump to the next step. If Above 4G is there, enable it first.
Set Above 4G Decoding to Enabled. Highlight the option and press Enter. Choose Enabled from the dropdown. Don't worry about the technical explanation, just switch it on.
Look for Resizable BAR in the same menu. Scroll up or down slightly. After you enable Above 4G Decoding, the Resizable BAR option should now be visible. If it was greyed out before, it should be clickable now.

✓ Above 4G Decoding is now on. If Resizable BAR is now visible in the menu, proceed to enable it (next box). If it's still nowhere to be found, your BIOS might be outdated; skip ahead to the Intermediate section.

Enable Resizable BAR Easy

Locate Resizable BAR in the BIOS menu. While still in the Advanced or PCI Subsystem Settings menu, find "Resizable BAR", "Re-Size BAR Support", or "ReBAR". Location varies wildly; check under Advanced > PCIe settings, Advanced > PCI Subsystem, or even Chipset menus depending on your board.
Set it to Enabled or Auto. Highlight the option and press Enter. You'll see a dropdown with options like Enabled, Disabled, or Auto. Choose Enabled if available. If only Auto is offered, that's fine, it does the same job on modern systems.
Save and exit BIOS. Press F10 and confirm. Your PC will reboot into Windows.
Wait for Windows to fully load. Don't restart again immediately. Let it boot normally and settle for 30 seconds. Some systems need a moment to recognize the new settings.

✓ Resizable BAR is now enabled in BIOS. Next step: verify it actually took effect in Windows.

Verify Resizable BAR Status in Windows Easy

For NVIDIA GPUs: open NVIDIA Control Panel. Right-click on your desktop and select "NVIDIA Control Panel". If you don't see this option, the driver isn't installed or you have an older version. Click the NVIDIA icon in your system tray (bottom-right corner) if it's there.
Go to System Information. In the left sidebar, find and click "System Information". A new window opens showing your GPU details.
Look for Resizable BAR status. Scroll down slightly. You should see a line that says "Resizable BAR" with a "Yes" or "No" next to it. If it says Yes, you're done, ReBAR is live.
For Intel GPUs: use Intel Driver and Support Assistant. Download it from Intel's driver page. Open the app, and it will report whether ReBAR is enabled on your system.
For AMD GPUs: open AMD Radeon Settings. Right-click your desktop and select "AMD Radeon Settings". Go to Advanced and look for GPU Memory settings. You should see ReBAR status there.

✓ Resizable BAR shows Yes (NVIDIA) or Enabled (AMD/Intel). Feature is active and working. If it still shows No or Disabled, proceed to the Intermediate section, something didn't stick.

Advanced Enable Resizable BAR Fixes (30+ Minutes)

Convert Legacy/MBR Disk to UEFI/GPT Hard

This is the nuclear option. If your system is stuck in Legacy mode and your disk is MBR-partitioned, nothing else will work. Resizable BAR fundamentally requires UEFI firmware and GPT partitioning. The good news: the conversion can be automated, but there's always a small risk of boot failure if something goes wrong. Have a recovery USB handy before you start.

Back up your data. This is critical. Use an external drive or cloud service. If the conversion fails partway through, you want your files safe. Even with a successful conversion, things can go wrong.
Create a Windows recovery USB. On another PC, download the Windows Media Creation Tool from Microsoft. Create a bootable USB with your Windows version. You'll use this if things break.
Run the MBR2GPT conversion tool. This is built into Windows 10 and 11. Press Windows key + R, type cmd, right-click Command Prompt, and select "Run as administrator". Type: mbr2gpt /convert /disk:0 (assuming Disk 0 is your system drive; use mbr2gpt /list first if unsure). The tool will scan your disk and report whether conversion is safe. If it says yes, confirm and let it run. This takes 5-10 minutes.
Restart into BIOS after conversion. When complete, restart and enter BIOS (DEL key). Confirm that Boot Mode is set to UEFI, not Legacy. If your BIOS reset to Legacy, change it back now.
Verify Windows boots normally. Save BIOS changes and let Windows boot. It should load without error. If it does, you're converted. If Windows fails to boot, use your recovery USB to repair it or restore from backup.
Verify Windows now shows UEFI boot mode. Open System Information (msinfo32) again and confirm BIOS Mode shows UEFI. Check Disk Management and confirm your system drive now shows GPT as the partition style.
Re-enable Resizable BAR in BIOS if needed. If your BIOS reset to defaults during the boot-mode switch, go back in and enable ReBAR settings again: disable CSM, enable Above 4G Decoding, enable Resizable BAR.
Verify ReBAR status in Windows. Open your GPU control panel and check that Resizable BAR now shows Yes or Enabled.

✓ Disk converted to GPT and system boots in UEFI mode. Resizable BAR should now be available and working. If Windows failed to boot during this process, use your recovery USB to restore and consider seeking professional help, disk conversion failures are rare but serious if they go wrong.

Simplify PCIe Configuration and Isolate Hardware Issues Hard

If you've gone through all the above steps and Resizable BAR still isn't working, the problem might be an unusual hardware configuration or a genuine incompatibility. This advanced troubleshooting narrows it down.

Temporarily remove secondary GPUs or PCIe expansion cards. If you have a second GPU, a sound card, or a PCIe NVMe adapter, remove them temporarily. Restart and check ReBAR status. Sometimes multiple PCIe devices create conflicts that hide or disable ReBAR.
Reset PCIe to Auto or Default in BIOS. Go back into BIOS. Look for "PCI Latency", "PCIe Speed", "PCIe Link Speed", or "Slot Configuration" settings. Set any manual overrides back to Auto or Default. Some users lock PCIe speed to Gen 3 or Gen 4, and this can cause ReBAR enumeration to fail on Gen 5 systems.
Confirm motherboard and GPU are officially compatible. Visit your motherboard manual or the manufacturer's website. Search for a list of "Supported GPUs" or "ReBAR Compatibility". Compare it to your GPU model. If your GPU is listed as unsupported, ReBAR genuinely won't work, upgrade is needed.
Check BIOS changelog for ReBAR-specific fixes. Visit your motherboard's support page and read the BIOS changelog for your current version. Search for "Resizable BAR", "PCIe", or "GPU". If recent updates mention fixes for ReBAR enumeration or PCIe device detection, consider updating to the absolute latest BIOS version (even if you've updated recently).
Re-install GPU drivers using DDU (Display Driver Uninstaller). For NVIDIA and AMD, download DDU from Guru3D. Boot into Safe Mode, run DDU, select your GPU, and choose "Uninstall and restart". After restart, install the latest driver fresh. This removes any corrupted driver files that might prevent ReBAR detection.

✓ Hardware simplified, BIOS settings reset, and drivers cleanly reinstalled. Resizable BAR should now be detected if your hardware truly supports it. If it still doesn't work, your motherboard or GPU likely doesn't have ReBAR support in this configuration, and the feature cannot be enabled.

If you've worked through all three tiers above and Resizable BAR still isn't showing as enabled, it's time to contact Vivid Repairs for remote support. We can dig into BIOS dumps, driver logs, and hardware configs that are difficult to troubleshoot alone.

Important: If you converted your disk from MBR to GPT or made significant BIOS changes and Windows is now failing to boot, stop here and use your recovery USB. Attempting further changes without a working Windows install will only make things worse. Restart with a recovery disk and consult a specialist if you can't restore boot.

Preventing Future Enable Resizable BAR Issues

Once Resizable BAR is running, keep it that way. Most users will never need to touch these settings again, but a few practices help.

Keep BIOS updated but don't obsess over it. Check for updates every 6 months. Manufacturers release BIOS updates for stability, security, and feature support. Resizable BAR compatibility improves with newer firmware, especially on older boards. Never update BIOS for a minor feature unless you have a specific reason (e.g., a game just started supporting ReBAR and your BIOS is old).

Document your BIOS settings before making changes. Take a photo of your screen showing CSM, UEFI mode, Above 4G Decoding, and Resizable BAR status. If you ever need to reset or troubleshoot, you'll know exactly what the working configuration looked like.

Keep graphics drivers current. Update your GPU driver every 3 months or when a major update is released. ReBAR support improves with each driver generation, and newer games often have better ReBAR optimization.

Verify ReBAR after each graphics driver update. Open your GPU control panel after installing a new driver and check that ReBAR still shows Yes or Enabled. Sometimes a driver update can reset this status (rare, but it happens). Catching it early saves frustration.

Use UEFI boot with CSM disabled on all new systems. Once your system is in UEFI mode with CSM off, leave it there. This is the standard for modern hardware and is required for Resizable BAR, NVMe SSD speed, Secure Boot, and other modern features.

Enable Resizable BAR Summary

Resizable BAR is a powerful feature hiding just below the surface of your GPU. The reason most people can't find it isn't because it's mysterious, it's because BIOS menus are confusing and modern features are locked behind older, outdated settings like CSM and Legacy boot mode.

Start by disabling CSM, enabling UEFI boot, and turning on Above 4G Decoding. Most of the time, that's all you need. If Resizable BAR still doesn't appear, update your motherboard BIOS. If it's still missing after that, verify Windows is in UEFI mode, update your GPU driver, and re-check. On rare occasions you might need to convert an old MBR disk to GPT, but that's a last resort.

Once enabled, verify the setting in your GPU control panel (NVIDIA Control Panel, Intel Driver Assistant, or AMD Radeon Settings). A "Yes" or "Enabled" status means the feature is live. You may not see a dramatic FPS boost in every game, but newer titles designed to use Resizable BAR will benefit. And now that you know how to enable Resizable BAR, you can actually use the feature instead of leaving performance on the table.

enable Resizable BAR