AMD Smart Access Memory (SAM) is AMD’s branded implementation of PCIe Resizable BAR. On a compatible system, enable it by using UEFI boot mode, disabling CSM, turning on Above 4G Decoding, and enabling Re-Size BAR Support (or setting it to Auto). Check compatibility and your Windows boot mode before changing firmware.
What Smart Access Memory does
Normally, the processor accesses a graphics card’s VRAM through a relatively small address window. Resizable BAR allows the CPU to map a larger portion—or, where supported, all—of the discrete GPU’s memory address space. AMD presents that capability as Smart Access Memory.
SAM is not extra VRAM, an overclock, or a frame-generation feature. It is a PCI Express memory-mapping capability. Intel and other vendors generally call the same underlying standard Resizable BAR; motherboard firmware may label it Re-Size BAR, Resizable BAR, SAM, or Clever Access Memory. See AMD’s overview at AMD Smart Access Memory and Intel’s technical explanation at Intel Resizable BAR support.
Performance is workload-dependent. Some games and applications can improve, while others change little. Results vary with the game, driver, resolution, processor, graphics card and firmware. SAM is free when your existing platform supports it, but it is not a guaranteed frame-rate increase.
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Check whether your PC supports SAM
Support is determined by the complete platform, not just the Radeon model. AMD’s published compatibility material identifies the following broad desktop combinations:
| Component | Broad AMD guidance | Important qualification |
|---|---|---|
| Graphics card | Radeon RX 5000 series or newer | OEM systems, firmware and unusual configurations can impose additional limits. |
| Processor | Ryzen 3000 desktop series or newer; AMD desktop kits beginning with 4800S and later are also listed | AMD’s published list includes exceptions such as Ryzen 5 3400G and Ryzen 3 3200G. Check the exact CPU and board combination. |
| Motherboard | AMD 500-series or newer, with a suitable BIOS | The required firmware and AGESA support depend on the board model and revision. |
| Laptop or prebuilt | Vendor-specific | The BIOS may hide the controls, enable SAM automatically, or require the manufacturer’s graphics driver. |
These are platform guidelines rather than a guarantee for every cross-generation combination. Check the support page, manual and BIOS notes for your exact motherboard, laptop or prebuilt model. AMD’s published references include RX 6000-series compatibility information and a launch-era reference with AGESA requirements. The original launch combinations and driver versions are not the only current way to use the underlying Resizable BAR feature.
On some MSI notebooks with Ryzen 5000H processors and Radeon RX 6000M graphics, MSI says SAM is enabled by default and cannot be manually switched. That is model-specific, not a general laptop rule; see MSI’s SAM guidance.
Confirm that Windows boots in UEFI mode
Do this before disabling CSM. A Windows installation using Legacy BIOS mode may stop booting when CSM is turned off.
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- Press the Windows key and type System Information.
- Open the System Information app.
- Find BIOS Mode.
- Continue only if it says UEFI. Back up important files before making firmware changes.
If BIOS Mode says Legacy, leave CSM enabled for now. Converting an MBR installation to GPT with Microsoft’s MBR2GPT utility may be possible, but it is a separate system-maintenance operation. Read Microsoft’s requirements, validate the disk and create a recovery plan before attempting it; do not treat conversion as a casual SAM toggle.
Update the motherboard BIOS and graphics driver
- Identify the exact motherboard model and revision (or the exact laptop/prebuilt model).
- Download firmware only from that manufacturer’s support page. Match the model and revision exactly.
- Read the vendor’s flashing instructions and do not interrupt power during the update.
- Record your current settings. A BIOS update can reset memory profiles, fan curves, boot order and other preferences.
- After the update, restore only the settings you actually need.
- Install a current Radeon Software Adrenalin package for your GPU and Windows version. On a laptop or OEM desktop, use the manufacturer’s driver if AMD’s package causes compatibility problems; AMD notes that OEM drivers may be required on some systems in its driver release notes.
Do not install a beta BIOS unless the manufacturer specifically requires it for your model. A BIOS update is normally free, but it carries model-selection, interruption and configuration-reset risks.
Enable SAM in BIOS or UEFI
Names and locations vary by motherboard model and firmware revision. The following sequence is the common pattern.
- Restart the PC and enter firmware setup. Begin tapping Delete or F2 immediately after powering on; some systems use F10, F11 or F12. The motherboard or system manual is authoritative.
- If the firmware opens in an Easy or simplified view, switch to Advanced Mode.
- Look under a menu such as Advanced, PCI Subsystem Settings, PCIe/PCI Configuration, I/O Ports or Chipset.
- Set Above 4G Decoding to Enabled.
- Set Re-Size BAR Support to Enabled or Auto, following your firmware manual. Some boards enable Above 4G Decoding automatically when Re-Size BAR is selected; check both settings.
- Open the Boot menu and set CSM, Compatibility Support Module or Legacy Compatibility to Disabled.
- Save changes and reboot.
Typical vendor locations are examples, not universal paths:
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- MSI: Advanced → PCI Subsystem Settings.
- ASRock: Advanced → PCI Configuration.
- ASUS: Advanced → PCI Subsystem Settings or a related PCIe configuration menu.
- Gigabyte: Settings or Advanced Mode → I/O Ports.
ASRock’s BIOS guides show the relevant options under PCI Configuration for example B650 and X870 firmware: B650 BIOS guide and X870 BIOS guide. Intel’s generic requirements likewise call for UEFI boot, disabled CSM, Above 4G Decoding and Re-Size BAR enabled or set to Auto.
On fast-boot systems, you can enter firmware from Windows: Settings → System → Recovery → Advanced startup → Restart now → Troubleshoot → Advanced options → UEFI Firmware Settings.
Verify that SAM is active
Radeon Software Adrenalin
Open Radeon Software and inspect the GPU information, performance, tuning or Smart Technology area. The label and location change between driver versions. A status such as Enabled or Available is useful evidence, but do not rely on an old screenshot or a historical menu path.
GPU-Z or another hardware-information utility
Use a current hardware-information utility with a Resizable BAR status field. This gives you an independent check of what the GPU and platform negotiated, rather than relying only on BIOS settings.
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BIOS settings
Above 4G Decoding enabled and Re-Size BAR set to Enabled or Auto confirm that firmware is configured correctly. They do not always prove that Windows and the graphics driver activated the feature, so pair this check with Radeon Software or a hardware-information utility.
MSI notebook-specific check
For certain MSI notebooks, MSI says that Large Memory Range under the discrete GPU’s Resources tab in Device Manager indicates SAM is enabled. This is an OEM-specific diagnostic, not a universal Windows rule.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.If Re-Size BAR is missing or SAM is unavailable
The option is missing
- Confirm the exact motherboard model and revision and update to a supported BIOS if appropriate.
- Switch to Advanced Mode and search for Resizable BAR, Re-Size BAR, SAM or Clever Access Memory.
- Check that CSM is disabled and that the GPU is recognized correctly.
- Review the board manual and release notes. Laptop and OEM firmware may intentionally hide the setting.
The option is greyed out or keeps resetting
Load optimized BIOS defaults, save, reboot into firmware and configure only UEFI boot, CSM, Above 4G Decoding and Re-Size BAR first. A BIOS reset can also have reverted the setting. If it repeatedly disappears, contact the motherboard or system manufacturer rather than forcing an unofficial BIOS modification.
Windows will not boot after CSM was disabled
- Re-enter BIOS/UEFI.
- Re-enable CSM or Legacy Compatibility.
- Restore the previous boot order and configuration.
- Boot Windows and check System Information → BIOS Mode.
- Back up the system before considering an MBR-to-GPT conversion.
Re-enabling CSM is the immediate recovery step; converting Windows to UEFI is a separate operation that requires validation and a backup.
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SAM still reports unavailable
- Recheck GPU, CPU, motherboard and OEM compatibility.
- Confirm the BIOS is current for the exact model.
- Confirm Windows uses UEFI mode and CSM is disabled.
- Enable Above 4G Decoding and Re-Size BAR (or Auto).
- Install a current Radeon driver, or the OEM driver on a laptop or prebuilt.
- Perform a full Windows reboot, then check with a second verification method.
- If settings remain inconsistent, reset BIOS to optimized defaults and repeat the minimal configuration.
Do not use registry edits, unofficial BIOS files or a forced driver switch to manufacture support.
Should you leave SAM enabled?
Usually, it is worth testing because it has no separate license or subscription cost. Use a repeatable benchmark in the games you actually play, with the same resolution, settings and driver, once with SAM enabled and once disabled. Keep it enabled if it helps or makes no measurable difference and the system remains stable; turn it off if it causes instability or a repeatable regression.
Do not replace a working CPU, motherboard or graphics card solely for SAM. A hardware upgrade should be justified by the broader performance, memory, power and feature gains. Resizable BAR is also used on some Intel and NVIDIA platforms under their own support policies, but the AMD procedure above applies to Radeon systems.
Quick Recap
How to disable SAM
- Enter BIOS/UEFI.
- Set Re-Size BAR Support to Disabled.
- Disable Above 4G Decoding only if your board’s documentation requires it for this configuration.
- Re-enable CSM only when the Windows installation requires Legacy boot; changing CSM can affect bootability.
- Save, reboot and verify the resulting status in Windows.
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