AMD Smart Access Memory technology works with Ryzen 5000 and Radeon RX 6000 — and not exclusively. In fact, NVIDIA and Intel claim that this is simply a PCI Express feature that is also supported by GeForce and Intel Arc graphics cards. In some cases, even over PCIe 3.0, gaming performance gains can reach up to 15%, although it ultimately depends on the specific scenario.
This article explains how to enable AMD Smart Access Memory using the Re-Size BAR Support and Above 4G Decoding settings as examples. My test systems include a Ryzen 5 3600 with an MSI B450 Gaming Plus MAX and an ASUS STRIX RX 580 8 GB, as well as a Ryzen 7 7700X with a GIGABYTE B650 AORUS ELITE AX and an RTX 3080 Ti 12 GB. Real-world testing confirms that enabling this feature is worthwhile.
Table of contents:
AMD Smart Access Memory technology. According to AMD, previously the CPU could access only a portion of the video memory, which limited performance. However, PCI Express bandwidth is significantly higher. The technology expands the data channel, allowing the GPU to make full use of its memory.
In the BIOS, these features are located next to each other:
Important! Smart Access Memory requires UEFI mode and a drive using the GPT partition style. If Windows 10 was installed in MBR boot mode, it will not be possible to enable Resizable BAR. Compatibility Support Module (CSM) must be disabled. In Windows 11, UEFI mode and GPT are used by default.
| Motherboards | Processors | Video cards | Drivers |
| X570, B550, A520 chipsets, as well as X470 and B450 (after a BIOS update). | AMD Ryzen 5000 and 3000 series (except Ryzen 5 3400G and Ryzen 3 3200G). | AMD Radeon RX 6000 (RX 6900 XT, RX 6800, RX 6700), RX 5000, and RX 5500 XT. | AMD Radeon Software Adrenalin Edition 20.11.2 or newer. |
| Z690, H670, B660, Z590, B560, Z490, B460, and some Z390 boards. | Intel 10th and 11th Gen Core S-series, 12th Gen and newer. | All Intel Arc discrete GPUs (including mobile) require it. | |
| Official support for GeForce RTX 3060 and newer; may require vBIOS updates. | Supported from Game Ready Driver or NVIDIA Studio Driver version 465.89 onward. |
In the GPU-Z application, all the criteria required to support this feature are displayed. These can be seen using my laptop with a GeForce RTX 3080 Ti as an example. If “Yes” is shown next to each item, it means that everything is enabled and working correctly.
And at the bottom, we can see BAR0, BAR1, and BAR2 — these are separate Base Address Registers (BARs), i.e. memory regions of the device exposed to the OS and CPU via PCIe. On my previous RX580, only a single BAR0 was present — 8192 MB. On a mobile RTX 3080, BAR0 is 16 MB (responsible for GPU registers and control), BAR1 is 16384 MB (VRAM), and BAR2 is 32 MB (reserved region).
The enabling process is universal. In the BIOS of my motherboard, go to Advanced > PCIe/PCI Subsystem Settings > Re-Size BAR Support. Set it to Enable, and Above 4G Decoding/Crypto Currency mining will also be enabled. Make sure to Save Changes and Reboot.
By the way, when updating the article, I tried to find and disable Above 4G MMIO BIOS Assignment on my laptop. It could not be re-enabled until I had to reset all settings. Depending on the manufacturer and BIOS version, the location and name of this setting may vary.
| Motherboard | BIOS Section | Settings |
| MSI | Advanced > PCIe/PCI Subsystem Settings Advanced > System Agent (SA) Configuration | Re-size BAR Support Above 4G Decoding/Crypto Currency mining Above 4GB MMIO BIOS assignment |
| ASRock | Advanced > Chipset Configuration Advanced > PCI Configuration | C.A.M. (Clever Access Memory) Re-Size BAR Support Above 4G Decoding |
| ASUS | Advanced > PCI Subsystem Settings EZ Mode > Resize BAR > On | Resizable BAR Support Above 4G Decoding |
| Biostar | Advanced > PCI Subsystem Settings Chipset > System Agent (SA) Configuration | Re-Size BAR Support Above 4G Decoding Above 4G MMIO BIOS Assignment |
| Gigabyte | Advanced Mode > Settings > IO Ports | Re-Size BAR Support Above 4G Decoding |
| Colorful | Advanced > ChipSet | Re-Size BAR Support Above 4GB MMIO BIOS assignment |
| Evga | Advanced > PCIe Configuration | Resizable BAR Support Above 4G Memory Assignment |
In the NVIDIA driver, it already specifies which games support Resizable BAR. Using the NVIDIA Profile Inspector tool, you can open the profile for Forza Horizon 6 and see that it has already been tested and that optimal settings have been defined.
In this way, you can test ReBAR in any game. It is worth noting that the maximum value does not always improve performance. There are cases where 1.5 GB performs better than 1 GB by 10 FPS, but if you set it to 8 GB, performance may decrease. In practice, you may only need the rBAR settings — Enable and Size Limit.
| rBar – Enable | Enable or disable Resizable BAR usage for the game profile. |
| rBar – Flags (0x000F00BE) | 0x00000000 — the feature is completely ignored by the driver for this game; 0x00000001 — enables full access to VRAM without restrictions; 0x00000003 — optimizes real-time high-resolution texture streaming. |
| rBar – Flags (0x000F00BF) | 0x00000000 — no restrictions, for optimized projects; 0x40000000 — 1 GB limit, for games that may use large amounts of VRAM; 0x80000000 — loading of memory blocks up to 2 GB. |
| rBar – Intel CPU Exclusion | Allows disabling the feature on certain Intel CPUs. |
| rBar – Options | 0x00000000 — Auto 0x00000001 — Default mode 0x00000002 — Compatibility mode 0x00000004 — Cautious (Stable) mode 0x00000008 — Aggressive (Full) mode. |
| rBar – Size Limit | Size limit mapping: 0x0000000040000000 = 1 GB 0x0000000080000000 = 2 GB 0x0000000100000000 = 4 GB 0x0000000200000000 = 8 GB. |
We use the universal application HWiNFO64. Run the Full mode, and in the Video Adapter list select your GPU — in my case: NVIDIA GeForce RTX 3080 Ti Laptop. Locate Resizable BAR Support and Resizable BAR (ReBAR) State.
In the Win+X menu, open Device Manager. Expand the Display adapters list and select your Graphics card. In the Resources section, an entry called Large Memory Range will appear. As a reminder, before enabling this technology, it was simply labeled Memory Range there (apparently, something has changed after all…).
The GPU-Z application also displays some of this information. In the Graphics Card tab, Resizable BAR is set to Enable (which is a good sign). Expand the Advanced section and select PCIe Resizable BAR from the list. Instead of BAR0 being 256 MB, it is now 8192 MB. This is a significant change, but it still needs testing — so far, I haven’t noticed any difference.
In AMD Software: Adrenalin Edition, go to Performance > Settings. At the bottom, AMD SmartAccess Memory should be Enabled, allowing the full available memory to be used. If it is Disabled, only the default 256 MB of memory will be used.
If you are an Intel Arc user, this feature should be enabled. In Intel Graphics Software, Resizable BAR is shown in green. You can open Settings > System to get more information.
With NVIDIA drivers, things are somewhat limited. In the classic NVIDIA Control Panel, go to System Information, where you can find the Resizable BAR entry. However, it has largely been replaced by the NVIDIA App. As soon as it gains the ability to check whether this feature is working, we’ll cover it.
MSI Center shows whether Resizable BAR is enabled. EVGA Precision X1 also has a dedicated section where you can check the status and compatibility. For example, if a graphics card vBIOS or driver update is required, it will be shown there.
Conclusions
My motherboard is fine — the BIOS has been updated. After enabling AMD Smart Access Memory, the RX 580 8 GB graphics card now shows a large memory range. At the same time, the GPU-Z application reports that GPU Hardware Support and Graphics Driver Support are not supported. However, performance still increases even without using a modified driver.
On the GIGABYTE B650 AORUS ELITE AX motherboard with an RTX 3080 Ti, everything works fine out of the box. However, by default, Resizable BAR is not enabled. Once everything is enabled, the NVIDIA driver will determine which games can use it and how. Using NVIDIA Profile Inspector, you can force-enable Resizable BAR for a game.
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