What is the resizable bar on a GPU and should I use it?

Your GPU isn’t the only component involved in drawing graphics on your screen. The CPU plays an important role in helping the GPU render images, and resizable BAR technology improves the way these two main components can work together seamlessly.

The CPU-GPU relationship

You may have heard of a CPU or GPU “bottleneck” before, and resizable BAR exists to deal with a very specific type of bottleneck that can occur between the CPU and GPU when they work together to draw the next frame.

That naturally begs the question of why the CPU is involved with the GPU in the first place. The two types of processors are good at different things. In a video game, for example, the CPU is responsible for driving animation, calculating the results of physical simulations, character behavior, etc. The GPU can’t draw the next frame until it knows where the objects should be, so it has to wait for the information from

Resizable BAR and smart access memory

Resizable BAR is a specific term for NVIDIA GPUs, but as is often the case, its main competitor, AMD, has its own version of the same technology. AMD calls its version Smart Access Memory or SAM, but in general, both features do the same thing in more or less the same way.

Without this feature, the CPU can only get data to process from the GPU memory in 256MB chunks. This has never been a problem until very recently. After all, it took many years for GPUs to have that much total memory. Even with a size of a few gigabytes, it doesn’t take time to review all 256 MB at once.

However, at the time of writing, GPU memory sizes typically range from 6GB to 12GB, with larger allocations becoming inevitable in the future as resolutions increase, detail levels improve, and technologies like ray tracing really push the limits of memory.

That’s where SAM or Resizable BAR comes into the picture, literally. With this feature enabled, the CPU can access the entire “frame buffer” (another name for GPU memory), meaning it can quickly find and process the data it needs.

It also reduces the amount of transfers between the CPU and the GPU and allows the CPU to only request data from the GPU memory when it needs it and from exactly the right place. In theory, this means that both the CPU and GPU will receive a performance boost because the amount of overhead and traffic is reduced.

Variable Size BAR Requirements

So far this feature sounds great, but who can actually use it? The truth is that resizable BAR is actually a feature of the PCIe standard. That is the GPU protocol to communicate with the rest of the computer.

It is optional for a motherboard, GPU, or CPU to support the feature, and only the latest components offer the option. All three components must support variable-size BAR or SAM.

10th Gen Intel CPUs and newer support resizable BAR, as do Zen 3 and newer AMD Ryzen CPUs. For Intel 10th Gen CPUs, only select chipsets are supported, but all 11th Gen or newer chipsets should be supported.

You will need an NVIDIA 30 series card; most of them are ready to go right out of the box. However, if you purchased a Founder’s Edition card, you may need to perform a firmware update to enable the feature. Speaking of firmware updates, you’ll probably also want to do one for your motherboard while you’re at it.

To use AMD SAM, you need a 6000 series card and a Ryzen 5000 or 3000 CPU, except for 3400G and 3200G models. You also need a motherboard with an AMD 500 chipset or 400 chipset combined with the 3000 series CPUs on the support list.

Assuming you have all the necessary components, with their latest firmware versions, you can enable resizable BAR or AMD SAM from your computer’s BIOS/UEFI menu. You’ll need to consult your motherboard documentation (or look up the information at boot) to see which key to press to access the menu.

Does resizable BAR make a difference?

At this time, it doesn’t seem like this feature will make much of a difference to real-world game performance. While it does increase performance in some titles, the improvement is modest and can even worsen performance in some cases.

NVIDIA, for its part, automatically disables the resizable BAR for games whose performance worsens with the feature enabled, so you really have no reason not to take advantage of it. You’ll get a small performance boost in many games, and you won’t get worse performance in games that aren’t whitelisted. If resizable BAR is causing you any serious problems, you can disable it in the BIOS.

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