- Above 4G Decoding allows mapping GPU memory above 4GB, which is essential to take advantage of modern graphics cards and multi-GPU configurations.
- Resizable BAR (or SAM on AMD) requires Above 4G Decoding enabled and can significantly improve performance and smoothness in certain games.
- Compatibility depends on CPU, motherboard, BIOS and GPU; AMD, NVIDIA e Intel ARC supports these functions, but requires drivers and updated firmware.
- Some devices may experience side effects (USB, mouse, stability), so it's advisable to test with caution and, if necessary, perform a complete CMOS reset.
If you've been tinkering with the BIOS of your modern motherboard, you've probably come across these options. Above 4G Decoding and Resizable BAR (or SAM) without really knowing what they do. Many videos and forums talk about activating these functions as if it were some kind of "hidden turbo" for your graphics card, but some people have also experienced strange problems when trying to use them.
In this article we will calmly examine exactly what these technologies are, What are they for, what real profit can they give you in games?what risks or side effects may appear and how to activate them correctly in the BIOS depending on the type of hardware whichever you have (AMD, NVIDIA, or Intel ARC). Everything is explained in Spanish (Spain), without unnecessary technical jargon, but with the level of detail that many of us appreciate when opening the BIOS.
What exactly is Above 4G Decoding?
The first thing is to understand what problem this option solves. A modern graphics card is almost like a small computer inside yours: it has its own BIOS, dedicated video memory, power circuitry and a graphics processing unit (GPU)However, to do anything useful, it needs to constantly communicate with the CPU via the PCI Express bus.
For many years, due to limitations inherited from 32-bit systems, the memory area reserved for mapping PCIe devices, including graphics, It was restricted to the first 4 GB of address spaceIn other words, all input/output (MMIO) communication to the GPU had to fit into that lower memory range, even if you had 16, 32 or more GB of RAM installed.
With the widespread arrival of the OS And with 64-bit processors, that historical limit became irrelevant. Today, hardware and software can handle much larger amounts of memory: At a theoretical level, astronomical figures (exabytes) can be reached.and in real desktop implementations, up to hundreds of terabytes of addressable space are handled.
Above 4G Decoding is precisely the BIOS option that allows you to take advantage of that extra space: Enables the use of memory addresses above 4 GB to map PCIe deviceslike your GPU. This way, the system isn't as limited when it comes to reserving space for the graphics card and other devices, especially when we're talking about cards with a lot of VRAM or configurations with multiple GPUs.
Relationship between Above 4G Decoding and Resizable BAR/SAM
Once you understand the above, it makes sense why many BIOSes require you to enable the Resizable BAR before activating it. Above 4G Decoding as a prerequisiteThey are different but closely related technologies.
Resizable BAR (or “Re-Size BAR Support” in BIOS) is a PCI Express feature that allows the CPU to access GPU memory more flexibly. Traditionally, the system mapped only a small window of the graphics card's VRAM (for example, 256 MB) and moved it around as needed; with Resizable BAR, That window can be made much larger and even encompass the entire VRAM, as long as the hardware supports it.
In the AMD ecosystem, this technology is marketed as SAM (Smart Access Memory)But technically, it's the same as Resizable BAR. Modern NVIDIA cards and Intel ARC cards also support this feature, provided the CPU, motherboard, and GPU are compatible and your BIOS and drivers are up to date.
Therefore, on many motherboards (for example, certain MSI or Gigabyte models) the typical path within the BIOS is something like this: go to advanced mode, enter the PCI Express settings, first enable Above 4G Decoding and, once done, the option will appear or be enabled. Resizable BAR or “Re-Size BAR Support”, which you can leave on Auto or Enabled.
Performance benefits: real-world examples and in-game improvements
Beyond the theory, what's really interesting is whether it makes a difference while playing. There are very clear testimonials from users who, by activating Above 4G Decoding and Resizable BAR, They have seen very considerable improvements in specific titles, especially in heavy open-world games or those with a lot streaming of data.
For example, a player with a AMD RX 6600 with overclock with AMD Ryzen Master or Intel XTU32 GB of RAM at 3200 MHz and an Intel i5-11600KF I was having trouble maintaining a stable 75 fps in Forza Horizon 5 using Proton. LinuxThe frame rate fluctuated between 60 and 90 fps, and the game suffered from constant stuttering. With all settings on Ultra and TAA enabled, performance barely reached 54 to 72 fps.
After entering his Gigabyte BIOS, he enabled the “Above 4G Decoding” option, and upon doing so, the Resizable BAR setting appeared, which he left on Auto. After that, Forza Horizon 5 went from running at a constant 110-115 fpsWith Ultra quality, TAA enabled, and no trace of the annoying stuttering I had before, all using Proton 7.0-3.
Since his MSI monitor only supports FreeSync up to 75 Hz, he locked the FPS at 75, and even then, it never drops below that. The player describes the experience as spectacular: Total fluidity, without those micro-cuts every few secondsThis is especially annoying in a racing game. In fact, he mentions that he didn't even know that feature was available and is now eager to see the improvements in other titles that were already working well in [the game/platform]. Windows.
This type of case perfectly illustrates the potential of Above 4G Decoding + Resizable BAR in certain hardware and game combinations: It's not magic, but in some titles it can mean significant performance leaps., both in average fps and, above all, in stability and elimination of stuttering.
How to enable Above 4G Decoding and Resizable BAR in the BIOS
If your curiosity has been piqued and you want to try it, the first step is to enter your computer's BIOS/UEFI. On desktop computers, this is almost always the classic key press. Press Delete (Del), F2 or another key during the BootBut portable It can vary quite a bit depending on the manufacturer, so it's best to check the official website or the manual.
Once inside, the exact path to find these options depends heavily on the brand and model of your motherboard. On many modern MSI motherboards with an AM5 socket, for example, you need to navigate to advanced BIOS mode Then go into the PCIe or CPU/PCI Subsystem settings. That's where the "Above 4G Decoding" option usually appears.
When enabled, the BIOS allows mapping memory addresses above 4 GB for the GPU and other devices. Immediately afterward, or even on the same screen, You will see the option for Resizable BAR / Re-Size BAR SupportMany guides recommend leaving it on Auto so that the system manages it according to the detected compatibility, but you can also force it to Enabled if your hardware is fully compatible.
On Gigabyte, ASUS, and other motherboards, the process is similar, although the menus have different names. On some models, Above 4G Decoding may also be linked to mining options. cryptocurrencies, , under names like “Crypto Currency mining”, since it was used (and is still used) to facilitate the use of multiple GPUs in mining tasks.
A key point is that for all of this to work properly, it is usually necessary to have the CSM (Compatibility Support Module) disabled and use UEFI boot with GPT partitionsIn addition, a relatively recent BIOS version and current graphics drivers are almost always required, especially for NVIDIA and Intel ARC, which have incorporated Resizable BAR support through updates.
Compatible with AMD, NVIDIA, and Intel ARC
Although there's a lot of talk about Above 4G Decoding and Resizable BAR as something almost exclusive to AMD, in reality All major modern GPU brands support it, with its nuances and trade names.
In the case of AMD, both in current Ryzen CPUs and Radeon GPUs, the function is usually presented as SAM (Smart Access Memory), which is simply a resizable BAR with their own branding. In the BIOS, you'll also see the Above 4G Decoding option, and it's essential to enable it for SAM to function; then, from within the Radeon Adrenalin software itself, in the "Performance" tab and the "Tuning" section, You can check and manage SAM activation And, to measure the effect, you can View GPU usage in Windows.
On NVIDIA, the latest generation RTX cards include support for Resizable BAR. Once enabled in the BIOS (along with Above 4G Decoding) and with the appropriate drivers, you can open the NVIDIA control panel and go to “System Information” To check if Resizable BAR is listed as enabled. It is usually shown as a specific line indicating "Yes/No".
Intel ARC GPUs also benefit greatly from this technology, to the point that manufacturers and analysts themselves strongly recommend it. have Above 4G Decoding and Resizable BAR enabledThe status of the function can be checked from your control panel in the "System info" section or similar, as well as in tools like GPU-Z, just like with NVIDIA and AMD.
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