What to Know About Resizable BAR?

Resizable BAR, also known as Base Address Register, is a technology that is rapidly gaining popularity in the world of gaming and other GPU-intensive applications. This technology enables a CPU to directly access the memory of a graphics processing unit (GPU), resulting in significant improvements in performance.

Though AMD is already using this technology with their Smart Access Memory which has been around since 2020, Nvidia improved this technology and gave a better performance on their 40xx Series of GPU.

The History of Resizable BAR

Resizable BAR has been around for a few years, but it wasn’t until NVIDIA’s release of its Ampere GPUs and AMD’s RDNA2 GPUs that it gained mainstream attention. The technology itself dates back to the days of PCI Express 2.0, but it wasn’t until the release of PCI Express 3.0 that it became standardized.

Before resizable BAR, graphics cards used a technique called “bounce buffering” to transfer data between the GPU and the CPU. Bounce buffering works by copying data between system memory and the graphics card’s memory, which is a slow and inefficient process. Resizable BAR, on the other hand, enables the CPU to directly access the GPU memory, resulting in much faster data transfers and improved gaming performance.

Technical Details

At a high level, resizable BAR works by enabling the CPU to directly access the GPU memory. When a game or other application requests data from the GPU, the CPU can access it directly without the need for copy operations between system memory and GPU memory. This results in faster data transfers, reduced latency, and improved performance.

To implement resizable BAR, both the GPU and the CPU must support it. Currently, resizable BAR is supported on AMD’s RDNA2 GPUs, NVIDIA’s Ampere GPUs, and Intel’s 11th Gen CPUs. It also requires support from the motherboard’s BIOS, so it’s important to ensure that your system supports resizable BAR before enabling it.

Benefits of Resizable BAR

The most significant benefit of resizable BAR is improved gaming performance. By enabling the CPU to directly access the GPU memory, data transfers are much faster, resulting in smoother gameplay and higher frame rates. Additionally, resizable BAR can also reduce latency, resulting in faster response times and better overall performance. Improved data transfer speeds can also benefit other GPU-intensive applications, such as video editing or machine learning.

Another benefit of resizable BAR is energy efficiency. By reducing the need for copy operations between system memory and GPU memory, resizable BAR can reduce the overall power consumption of your system, resulting in longer battery life for laptops and lower electricity bills for desktops.

Resizable BAR in Action

Real-world benchmarks have shown that resizable BAR can provide significant performance improvements in gaming. In some cases, frame rates have increased by as much as 20% in games like Assassin’s Creed Valhalla and Cyberpunk 2077. In addition, resizable BAR can also improve performance in other GPU-intensive applications, such as 3D rendering and machine learning.

Potential Issues

While resizable BAR can provide significant performance improvements, there are a few potential issues to be aware of. First, compatibility can be an issue with older hardware and software. Not all GPUs and CPUs support resizable BAR, and some games and applications may not be optimized for it. Additionally, there are security concerns related to the direct access of GPU memory by the CPU, although these risks are relatively low.