AtlasOS

GPU settings - Resizable BAR

Enable Resizable BAR (Base Address Register), also known as Smart Access Memory (SAM) on AMD systems, to improve communication between your CPU and GPU. This can significantly improve in-game FPS, sometimes by up to 15%, by allowing your CPU to access the GPU’s entire frame buffer at once.

How it works

When playing a game, your GPU requests textures, shaders, and other assets from your CPU. These are stored in the graphics card’s VRAM before being rendered.

Traditionally, the CPU could only access 256MB chunks of VRAM at a time, requiring multiple sequential transfers. As games have become larger and more complex, this limitation becomes more significant.

Resizable BAR allows your CPU to access the GPU’s entire frame buffer at once, enabling more efficient concurrent transfers and boosting performance.

Requirements

Resizable BAR requires the following graphics cards:

  • NVIDIA GeForce 30 series or newer
  • AMD Radeon RX 6000 Series or newer

Hardware Requirements

If you do not meet these specifications, it’s recommended to not enable the feature.

Update BIOS First

Before enabling Resizable BAR, update your BIOS. If you enable it first, the settings may not be visible in your BIOS, and you’ll need to repeat these steps after updating.

How to check if Resizable BAR is enabled

  1. Download GPU-Z and open the application
  2. Check to see if Resizable BAR is disabled or enabled
  3. GPU-Z allows you to see why it’s disabled. Click on Disabled to see more information about what you’re missing

How to enable Resizable BAR

  1. Boot into the BIOS by pressing the BIOS key while your PC starts

    • Commonly Del or F2 , but check your motherboard manual

  2. Disable Compatibility Support Module (CSM) from the Boot menu

  3. Enable the following options:

    • Above 4G Decoding
    • ReSize BAR Support (or similar wording)
    • These are usually found under PCI Subsystem Settings or on the main BIOS screen

  4. Save and exit the BIOS

  5. Verify it’s enabled using GPU-Z (see above)

Next steps

After enabling Resizable BAR: