Resizable BAR and AMD Smart Access Memory are often presented as competing gaming features, but they are closely related. Both change how the CPU accesses the graphics card’s VRAM. The goal is to reduce inefficient transfers and improve performance in games that benefit from larger, more flexible data access.
If your PC supports the feature, enabling it is usually worthwhile. It is not a universal FPS switch, and it will not fix shader stutter, insufficient VRAM, or a slow GPU.
What Resizable BAR actually changes
Resizable BAR is an optional PCI Express feature. In a traditional configuration, the CPU accesses the GPU frame buffer through smaller windows, moving game assets in repeated transfers. With Resizable BAR active, the CPU can access the full frame buffer and request larger assets as needed.
NVIDIA’s technical overview explains that modern games constantly move textures, shaders, and geometry between the CPU and GPU. Full frame-buffer access can make those transfers more efficient and allow multiple requests to occur without the same queueing behavior.
This does not add VRAM or make the PCIe link physically faster. It changes the size and organization of the addressable memory region.
Is Smart Access Memory different?
Smart Access Memory, usually shortened to SAM, is AMD’s implementation and branding around Resizable BAR for compatible Ryzen and Radeon systems. AMD describes it as giving the processor immediate, full access to Radeon graphics memory for faster transfers.
The underlying concept is therefore the same. “SAM” does not mean the PC has a second memory pool, and it is not a replacement for system RAM. On an all-AMD system, the firmware or AMD Software may use the Smart Access Memory name. Other combinations usually call it Resizable BAR or Re-Size BAR.
Compatibility has expanded over time, so do not rely on an old launch-day hardware list. Check the current support pages for your CPU, GPU, motherboard, and laptop model.
What hardware and firmware are required?
A working setup needs support across the entire chain:
- A compatible processor and motherboard chipset
- A motherboard BIOS or laptop firmware that exposes the feature
- A compatible graphics card and, on some older cards, an updated VBIOS
- A recent graphics driver
- UEFI boot configuration rather than a legacy-only setup
NVIDIA specifically notes that desktop support depends on the graphics card, motherboard, and driver. AMD’s Smart Access Memory documentation likewise ties support to selected Ryzen, Radeon, and motherboard configurations.
Laptops require extra caution because their BIOS options are often locked down. If the manufacturer enables the feature automatically, there may be no manual switch.
How to enable Resizable BAR or SAM
Update the motherboard BIOS and graphics driver first. If the graphics card manufacturer provides a VBIOS tool for your exact model, read its instructions carefully and never flash firmware intended for a different card.
In the motherboard’s UEFI menu, the relevant options are commonly named Above 4G Decoding and Re-Size BAR Support. AMD boards may display Smart Access Memory. Some systems also require the Compatibility Support Module, or CSM, to be disabled so Windows boots in full UEFI mode.
Option names and locations vary. Use the motherboard manual instead of copying a random set of screenshots. Changing CSM on an older Windows installation can prevent the system from booting if its system disk was configured for legacy BIOS mode.
How to verify that it is active
For a GeForce system, open the NVIDIA app or NVIDIA Control Panel and inspect the system information page for a Resizable BAR status. Radeon Software can report Smart Access Memory under its performance or tuning information. Hardware tools may also show a ReBAR status, but the graphics driver’s own report is the best first check.
If the motherboard option is enabled but the driver says the feature is off, check UEFI boot mode, Above 4G Decoding, GPU firmware, and the latest motherboard BIOS. On a laptop, consult the manufacturer before attempting any firmware workaround.
Does it improve every game?
No. The result depends on how a game streams assets and how the driver handles the title. Some games gain measurable performance, some change very little, and a poorly matched configuration can perform worse. That is why graphics drivers may use game profiles or expose per-game controls.
Resizable BAR also does not solve every type of hitch. If a game pauses when new effects appear, the cause may be shader compilation rather than memory transfers. Our shader compilation stutter guide explains that separate problem.
Should you turn it on?
Enable it when your CPU, motherboard, GPU, firmware, and driver officially support it. Leave the global driver behavior at its default first, then benchmark the same repeatable scene if you experiment with a per-game override.
Do not buy a new graphics card solely for Resizable BAR. Treat it as a free platform optimization, not a substitute for a faster GPU, adequate VRAM, or sensible game settings.