Resizable BAR, also called Smart Access Memory on AMD platforms, is a PCIe interface feature that lets your CPU see your GPU’s entire VRAM pool at once instead of in tiny 256 MB segments. Enabling it is free, takes five minutes in your BIOS, and on the right hardware configuration it unlocks measurable frame rate gains in CPU-bound scenarios. This guide walks through exactly how to turn it on, how to confirm it’s active, and what performance you can realistically expect at each resolution.
The Short Answer
Yes, you should enable Resizable BAR. The one condition that changes the calculus: your GPU must support it (RTX 3060 and newer, GTX 16 series with a compatible BIOS, or Radeon RX 6000 and newer) and your motherboard must offer Above 4G Decoding alongside the ReBAR toggle. If you’re running a CPU that bottlenecks at 1080p, the gains are real. If you’re already GPU-bound at 4K with a high-end card, the improvement is negligible.
How to Tell
Before and after enabling the feature, you need a reliable way to verify it’s active. Here are the concrete checks:
GPU-Z. Open GPU-Z (TechPowerUp’s free utility), go to the Advanced tab, and look for the “Resizable BAR” field. It will read either “Supported, Enabled” or “Supported, Disabled.” This is the single most definitive confirmation. If it says unsupported, your BIOS or GPU doesn’t offer the feature.
BIOS inspection. Enter your motherboard’s UEFI setup (typically DEL or F2 at boot). Navigate to the PCIe or Settings section. You should see toggles for “Above 4G Decoding” and “Resizable BAR Support” (sometimes labeled “ReBAR” or “Smart Access Memory” on AMD boards). Both must be enabled. Legacy CSM must be off.
In-game overlays. The NVIDIA GeForce Experience overlay and AMD Adrenalin software do not always expose ReBAR status directly, but MSI Afterburner with HWiNFO64 integration can pull the PCIe status. If the GPU VRAM mapping field shows a single large allocation rather than chunked accesses, the feature is working.
Task Manager and frame time deltas. On a borderline system (older CPU, high-refresh 1080p monitor), enable ReBAR, restart, and run a game with a built-in benchmark. Compare average FPS and 1% low. A shift of 3-10% in either metric, with no other variable changed, is the practical signal that the feature is contributing.
GPU usage percentage. In CPU-limited scenarios, Resizable BAR can reduce the number of memory-mapping calls the driver makes, which occasionally shows as slightly lower GPU utilization at identical frame rates. This is a subtle indicator and not a reliable standalone check, but it supports the other methods.
By Resolution
1080p
This is where Resizable BAR has the most measurable impact. At 1080p, frame rates are high and the CPU is frequently the limiting factor, meaning the PCIe memory-mapping overhead matters more. TechPowerUp’s RTX 3060 launch coverage and Hardware Unboxed’s cross-title testing in their Radeon RX 6000 and GeForce RTX 30-series evaluations consistently identified the 1080p range as the highest-gain scenario, with improvements typically falling between 4% and 12% depending on the title, with outliers above 15% in engine-limited games like Far Cry 6 and Borderlands 3.
1440p
At 1440p, the GPU workload grows large enough to mask much of the PCIe mapping overhead, but a CPU bottleneck can still persist on mid-range processors. Tom’s Hardware and TechSpot reported average gains in the 2-7% range at this resolution across their broader game test suites, with the upper end appearing in titles that stress VRAM streaming or have large texture working sets.
4K
At 4K, the GPU is almost always the limiting factor. The data from Gamers Nexus and Hardware Unboxed converged on a finding that most titles show 0-3% change at this resolution, and a meaningful number show zero difference. Gamers Nexus noted in their platform analysis that the overhead ReBAR addresses is simply too small a fraction of total frame time at GPU-bound settings to register on most benchmarks.
| Resolution | Typical Gain Range | Best-Case Title Example | Worst Case | Source Outlet |
|---|---|---|---|---|
| 1080p | 4-12% average, up to 15%+ in outliers | Far Cry 6, Borderlands 3 | 0-1% (GPU-bound titles) | TechPowerUp, Hardware Unboxed |
| 1440p | 2-7% | Assassin’s Creed Valhalla, Control | 0-1% | Tom’s Hardware, TechSpot |
| 4K | 0-3% | Horizon Zero Dawn (marginal) | 0% (no measurable change) | Gamers Nexus, Hardware Unboxed |
What to Do About It
The steps below apply to most modern platforms as of 2026. Specific menu names vary by motherboard vendor.
Step 1: Update your BIOS. Visit your motherboard manufacturer’s support page and flash to the latest BIOS version. On many boards shipped in 2021-2022, Resizable BAR support was added via a firmware update even though the hardware supported it from day one. Intel’s non-K 12th and 13th gen desktop CPUs required specific microcode revisions for full ReBAR compatibility.
Step 2: Enter UEFI settings. Reboot and press DEL or F2. Navigate to the Settings, Advanced, or PCIe submenu depending on your vendor.
Step 3: Disable CSM (Compatibility Support Module). This is critical. Resizable BAR requires pure UEFI boot mode. If your display is showing through a legacy boot path, you will need to reformat your boot drive to GPT and switch your Windows installation to UEFI mode. If you already installed Windows in UEFI mode (which most 2020+ systems use), simply toggle CSM off.
Step 4: Enable Above 4G Decoding. This toggle must be on. It appears in the same PCIe settings area.
Step 5: Enable Resizable BAR / Smart Access Memory. On Intel-based boards, look for “Resizable BAR Support” or “ReBAR Support.” On AMD 500- and 600-series boards, the toggle is often labeled “Smart Access Memory.” Set it to Enabled or Auto.
Step 6: Update your GPU driver. NVIDIA GeForce drivers from 471.96 onward and AMD Adrenalin 21.12.0 onward support ReBAR natively. On a clean install, the driver should auto-negotiate the feature if BIOS settings are correct.
Step 7: Verify. Boot into Windows, open GPU-Z, and confirm the Advanced tab reads “Supported, Enabled.”
Recommendation by User Type
Competitive 1080p esports player (360Hz monitor, Ryzen 7 or Core i7): Enable it immediately. You are the exact persona who benefits most. Every 1% of frame time reduction matters at 360 FPS.
1440p mid-range gamer (RTX 3060 Ti / RX 6700 XT, Core i5 or Ryzen 5): Enable it. The gains are modest but free, and your CPU is close enough to the bottleneck that some titles will show measurable improvement.
4K high-end gamer (RTX 4080+ / RX 7900 XTX, Core i9 or Ryzen 9): Enable it anyway. The performance difference will likely be invisible, but the feature carries no downside, no stability risk on modern drivers, and no measurable latency penalty.
Older platform (pre-RTX 3060 or pre-RX 6000 GPU): You cannot enable it. The hardware does not support the PCIe capability. Upgrade the GPU to get ReBAR access.
FAQ
Does Resizable BAR work with all GPUs?
No. On the NVIDIA side, RTX 30-series and RTX 40-series cards support it, plus the GTX 1650 Super with a BIOS update on select boards. AMD’s RX 6000 and RX 7000 series all support it. Older cards lack the required PCIe capability regardless of driver settings.
Can enabling Resizable BAR cause instability?
On current driver and BIOS versions, no credible reports of instability specific to ReBAR exist. The feature changes how memory is mapped, not how the GPU computes. If you experience issues after toggling it, the cause is almost certainly an unrelated BIOS setting (such as PCIe Gen speed negotiation) that you changed simultaneously.
Why doesn’t my BIOS show the option?
The most common reason is a BIOS version predating ReBAR support. Many boards received it via update. Second most common reason: CSM is enabled, which hides or grays out the toggle. Third: the motherboard chipset genuinely lacks support, which is limited to very low-end or pre-2019 boards.
Does it help with VRAM usage or stuttering?
Some users anecdotally report reduced stutter in open-world titles because the CPU can page larger texture blocks without repeated memory-mapping calls. However, controlled testing from Hardware Unboxed did not isolate a consistent stutter-reduction benefit. The measurable effect is on frame rate, not frame time variance, in the titles tested.
Sources and Methodology
Performance ranges cited in this article reflect published benchmark data from TechPowerUp (RTX 3060 and RX 6700 XT launch reviews and follow-up multi-title coverage), Hardware Unboxed (GeForce RTX 30/40-series and Radeon RX 6000/7000-series testing across resolutions), Tom’s Hardware (Smart Access Memory feature review and platform comparisons), Gamers Nexus (PCIe mechanism analysis and RTX 30-series benchmark suites), and TechSpot (multi-title GPU launch coverage). All figures are approximate ranges compiled from these outlets’ published results. No original benchmark testing was conducted for this article.
