How To Check If Resizable BAR Is Enabled Radeon
Resizable BAR (Base Address Register) allows your CPU to access the entirety of your Radeon graphics card's VRAM simultaneously, eliminating traditional data transfer bottlenecks. Verifying that this feature is active requires checking both your system's motherboard BIOS configuration and your AMD Adrenalin software utility in Windows.
Pre-Procedure Planning for Radeon ReBAR Activation
Before diving into configuration diagnostics, it helps to understand the underlying architecture and prerequisites required for Resizable BAR to function correctly. ReBAR is built on the PCI Express standard, specifically utilizing the PCIe protocol to optimize communication channels between the processor and the graphics subsystem. Activating it successfully yields measurable frame-rate improvements in modern titles and better overall memory resource allocation.
- Essential Hardware & Software: An AMD Ryzen processor (Zen 3 or newer recommended, though Zen 2 is supported on select boards), a compatible AMD Radeon RX 5000, RX 6000, or RX 7000 series graphics card, and a UEFI-capable motherboard running the latest AGESA microcode update.
- Mandatory Standards & Settings: Your system drive must be formatted as GPT (GUID Partition Table), and the operating system must run in native UEFI mode with CSM (Compatibility Support Module) permanently disabled. Secure Boot must also be supported, though it does not strictly need to be active depending on the motherboard manufacturer.
- Time & Effort Benchmark: The verification and potential configuration process takes approximately 10 to 15 minutes, with zero financial cost beyond your existing hardware stack.
Step-by-Step Procedure to Verify and Enable Resizable BAR
Step 1: Check Current Status in AMD Software Adrenalin Edition
The fastest way to check if Resizable BAR is enabled on a Radeon system without rebooting into the BIOS is by utilizing the official driver software interface. Right-click on your Windows desktop and select AMD Software: Adrenalin Edition to open the control panel. Navigate to the Performance tab located in the top menu bar, and then select the Tuning sub-tab beneath it. Scroll down the hardware metrics and configuration options until you locate the motherboard or GPU status indicators. Look specifically for the Resizable BAR metric; if it displays as Enabled, your hardware handshake is complete.
Pro-Tip: If the Adrenalin software indicates that Resizable BAR is disabled or unsupported, do not attempt driver reinstalls yet. The bottleneck almost always originates at the motherboard UEFI level, requiring a system reboot.
Step 2: Access Motherboard UEFI/BIOS Settings
Restart your computer and repeatedly press the designated entry key (usually Del, F2, or F12 depending on your motherboard manufacturer such as ASUS, MSI, Gigabyte, or ASRock) during the initial POST screen. Once inside the advanced BIOS interface, switch from EZ Mode to Advanced Mode (often toggled via the F7 key) to gain access to low-level PCIe configuration parameters. Because every motherboard vendor uses slightly different nomenclature, locate the tab governing system agents, peripheral settings, or PCI subsystem settings.
Step 3: Configure Above 4G Decoding and ReBAR Parameters
Inside the advanced PCIe configuration menu, locate the setting labeled Above 4G Decoding. Toggle this setting from Disabled to Enabled. Once Above 4G Decoding is active, a secondary option for Resizable BAR Support will appear directly beneath it or within a nearby submenu. Change this setting to Enabled or Auto.
Warning: If your system drive was originally installed under Legacy BIOS or MBR partitioning, enabling Above 4G Decoding and CSM-disabled UEFI mode will cause your operating system to fail to boot until you convert the drive format to GPT using Microsoft utility tools like MBR2GPT.
Step 4: Save Changes and Confirm in Windows
Press the designated save-and-exit key (typically F10) to commit your new BIOS changes and reboot the system back into Windows. Log into your user account, open the AMD Software: Adrenalin Edition application once more, and navigate back to the Performance and Tuning tabs. Confirm that the Resizable BAR status indicator now reads Enabled. You can additionally verify this via Windows Device Manager by locating your graphics card, opening its Properties, switching to the Resources tab, and checking for a large Memory Range exceeding the traditional 256MB limitation.
Radeon Resizable BAR Compatibility Matrix
| Hardware Generation | Minimum BIOS Version Required | VBIOS Flash Requirement | Expected Performance Gain |
|---|---|---|---|
| Radeon RX 5000 Series | AGESA Combo-AM4 v2 1.2.0.0+ | Mandatory VBIOS Update | 2% to 5% Average FPS |
| Radeon RX 6000 Series | AGESA Combo-AM4 v2 1.2.0.2+ | Factory Default or Update | 5% to 15% Average FPS |
| Radeon RX 7000 Series | AGESA AM5 1.0.0.7c or Newer | Factory Default | 3% to 12% Average FPS |
Common Site Failures and Field Fixes
- Root Cause: Adrenalin software continues to show Resizable BAR as disabled despite enabling it in the BIOS.
- Actionable Fix: Ensure that CSM (Compatibility Support Module) is entirely disabled in your BIOS. If CSM remains active, the system cannot allocate the 64-bit addressing space required for ReBAR.
- Root Cause: The system fails to boot into Windows with a black screen or infinite loop after enabling Above 4G Decoding.
- Actionable Fix: Your Windows installation is utilizing legacy MBR partitioning rather than UEFI/GPT. Clear your CMOS to restore default BIOS settings, boot into Windows, and convert your drive partition using the MBR2GPT command-line tool before re-enabling ReBAR.
- Root Cause: The Resizable BAR option is completely missing from the motherboard BIOS menus.
- Actionable Fix: Your motherboard is running an outdated firmware revision. Visit your motherboard manufacturer support website, download the latest stable BIOS update matching your specific board model, and flash the UEFI.
Frequently Asked Questions
Does Resizable BAR work with all processors on Radeon systems?
No. Resizable BAR requires platform-level support from both your CPU and motherboard chipset alongside your Radeon GPU. Generally, Intel Core processors from the 10th Generation onward and AMD Ryzen processors from the Zen 2 architecture onward fully support the feature when paired with an updated UEFI.
Will enabling Resizable BAR delete my personal files or Windows installation?
No. Simply toggling Resizable BAR, Above 4G Decoding, and disabling CSM does not modify or delete data stored on your storage drives. However, if your system previously relied on legacy boot modes, you may need to adjust partition tables, which requires careful execution.
How much of a performance boost will I actually see with Radeon ReBAR?
The performance increase varies significantly depending on the game engine, graphics API (DirectX 12 and Vulkan benefit the most), and resolution. While some titles see negligible differences, GPU-heavy games and modern AAA releases often experience a 5 to 15 percent increase in average frame rates and improved 1% low metrics.
Why does my older Radeon RX 580 or RX 590 not support Resizable BAR?
First-generation Polaris architecture lacks the native hardware and VBIOS architecture required to process large base address register allocations. Resizable BAR officially begins support with select late-model RX 5000 cards via VBIOS updates and is fully native to the RX 6000 and RX 7000 series.
Can I verify Resizable BAR status using third-party tools?
Yes. Aside from the AMD Adrenalin software, widely trusted third-party diagnostic utilities such as GPU-Z can instantly confirm activation. Open GPU-Z and look at the Resizable BAR field near the center of the main tab to see if it displays as Enabled.
Optimize your gaming performance today by verifying your BIOS settings and confirming your AMD Radeon hardware is running at its absolute maximum efficiency.
