Resizable BAR (ReBAR) Explained: Requirements and Benefits
Graphics · Updated · First published · By the Hardware Spec Index editors
Resizable BAR is a PCI Express capability that lets the CPU map the graphics card's entire VRAM into its address space instead of accessing it through a 256 MB window. AMD markets its implementation as Smart Access Memory.
Key facts
| Full name | Resizable Base Address Register |
|---|---|
| Default BAR window | 256 MB |
| AMD name | Smart Access Memory |
| BIOS settings | UEFI boot, CSM off, Above 4G Decoding on, ReBAR on |
| Typical gain | 0–10% depending on the game |
How it works
Without ReBAR, the CPU transfers data to the GPU through a fixed 256 MB base address register window, moving it in many small chunks. With ReBAR, the window can cover all VRAM, so large transfers such as textures can be written directly.
Requirements
ReBAR needs a supported CPU, motherboard firmware, graphics card and driver. In the BIOS, the system must boot in UEFI mode with the Compatibility Support Module (CSM) disabled, and both Above 4G Decoding and Resizable BAR must be enabled.
Performance
Gains vary by game, from none to around 10 percent; a few titles run slightly slower, which is why some drivers enable it per game. Some graphics architectures rely on ReBAR heavily and lose significant performance without it.
Top-ranked matching records
Highest normalized benchmark index among Graphics Cards, Motherboards in our database that match this guide. Rankings are data, not reviews.
| Model | Category | Benchmark | Price |
|---|---|---|---|
| Teralux GX-7066 Edge 32GB GDDR6X Graphics Card | Graphics Cards | 42,383 | $2,499 |
| Orbita GX-3989 Pro 32GB GDDR6 Graphics Card | Graphics Cards | 40,768 | $2,299 |
| Nexora GX-7181 Prime 32GB GDDR6X Graphics Card | Graphics Cards | 39,124 | $1,719 |
| Kyndral GX-7119 Prime 16GB GDDR7 Graphics Card | Graphics Cards | 38,614 | $1,559 |
| Veltrix GX-8107 Ultra 32GB GDDR6X Graphics Card | Graphics Cards | 38,351 | $1,509 |
| Teralux GX-5181 Prime 32GB GDDR7 Graphics Card | Graphics Cards | 35,236 | $1,349 |
| Veltrix GX-5189 Ti 24GB GDDR6X Graphics Card | Graphics Cards | 35,220 | $1,589 |
| Orbita GX-4156 Edge 16GB GDDR7 Graphics Card | Graphics Cards | 34,712 | $1,709 |
Frequently asked questions
How do I check if ReBAR is enabled?
Your GPU control panel or system information tool lists Resizable BAR status.
Do I need to reinstall Windows to enable ReBAR?
Only if Windows was installed in legacy BIOS mode; it must boot in UEFI mode, which may require converting the disk from MBR to GPT.
Does ReBAR work with older GPUs?
It requires firmware support on the graphics card; some older cards received updates, many did not.
Can ReBAR reduce performance?
In a small number of games, yes, which is why drivers may enable it selectively.
Is Smart Access Memory the same as ReBAR?
Yes, it is AMD's name for the same PCIe feature.
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Cite this page: Hardware Spec Index, “Resizable BAR (ReBAR) Explained: Requirements and Benefits”, https://vextor7.com/topics/resizable-bar (accessed 2026-10-22).