How to Enable Resizable BAR for Gaming (ReBAR Guide)
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Resizable BAR (ReBAR) lets your CPU access the full GPU memory at once instead of in small chunks, and in supported games that’s free FPS. This guide shows you how to enable it safely and confirm it’s actually working.
ReBAR gains vary by game — some see a nice boost, a few regress slightly. It’s easy to toggle, so test and keep what’s faster.
What is Resizable BAR?
Normally the CPU sees GPU video memory through a small 256 MB window. Resizable BAR (called Smart Access Memory on AMD systems) opens that window to the full VRAM, reducing overhead in games that benefit. NVIDIA, AMD, and Intel GPUs all support it on modern platforms.
Requirements
- A GPU that supports ReBAR (NVIDIA RTX 30-series and newer, AMD RX 6000 and newer, Intel Arc).
- A motherboard and CPU that support it (most boards from the last several generations, often after a BIOS update).
- UEFI boot mode with CSM (Compatibility Support Module) disabled.
Step 1 – Update your BIOS if needed
Older boards added ReBAR support via a BIOS update. If you don’t see the option, update first — carefully. See How to Update Your BIOS Safely.
Step 2 – Enable the right BIOS options
Enter BIOS by tapping Delete (or F2) at boot, switch to Advanced mode, and look for these:
| BIOS brand | Where to look |
|---|---|
| ASUS | Advanced → PCI Subsystem Settings → Above 4G Decoding + Re-Size BAR Support |
| MSI | Settings → Advanced → PCI Subsystem Settings → Above 4G Memory + Re-Size BAR |
| Gigabyte | Settings → Above 4G Decoding + Re-Size BAR Support |
| ASRock | Advanced → PCIe Configuration → Above 4G Decoding + Re-Size BAR |
- Set Above 4G Decoding to Enabled (required first).
- Set Re-Size BAR Support to Enabled (or Auto).
- Make sure CSM is Disabled (ReBAR needs pure UEFI).
- Save and exit (F10).
Step 3 – Confirm ReBAR is active
- NVIDIA: open NVIDIA Control Panel → System Information → look for Resizable BAR: Yes.
- AMD: AMD Software → Performance/Hardware → Smart Access Memory: Enabled.
- GPU-Z: the Resizable BAR field shows Enabled.
If it still says disabled, CSM is usually still on, or Above 4G Decoding wasn’t enabled.
Should you keep it on?
In most modern titles ReBAR is neutral-to-positive, so leaving it on is fine. A handful of games regress slightly — if you suspect that, benchmark with it on and off using benchmarking tools and keep whatever’s faster.
Related guides
- How to Update Your BIOS Safely
- How to Enable XMP or EXPO for Gaming
- Best NVIDIA Control Panel Settings for Gaming
- Testing PC Components Using Benchmarking Tools
Enabling Resizable BAR is a two-toggle BIOS change — Above 4G Decoding plus Re-Size BAR, with CSM off. Confirm it’s active in your driver software, then benchmark to lock in the gain.
Menu names vary by brand and BIOS version; if a label differs, apply the same logic: enable Above 4G Decoding first, then Re-Size BAR, and disable CSM.
Frequently asked questions
What does Resizable BAR actually do?
It lets the CPU access the GPU's entire memory at once instead of in small 256 MB windows, which removes overhead and improves performance in supported games.
How much FPS does Resizable BAR add?
Typically 0 to 10 percent depending on the game, with some titles seeing more. It is a free upgrade, so it is worth enabling even if the average gain is modest.
What do I need to use Resizable BAR?
A modern GPU, a compatible motherboard with the option in BIOS, UEFI boot mode with CSM disabled, and updated firmware. On AMD cards it is called Smart Access Memory.
Is enabling Resizable BAR safe?
Yes. It is a standard PCIe feature, and you can switch it off again in BIOS at any time if a specific game misbehaves.