NVIDIA GeForce RTX 4080 vs AMD Radeon RX 7900 XTX – Test of graphics cards with Resizable BAR enabled. Which will be faster?

The rivalry between NVIDIA GeForce RTX 4080 and AMD Radeon RX 7900 XTX graphics cards aroused a lot of emotions, especially if the final results did not meet the expectations of fans of one or the other manufacturer. Then, traditionally, the search for the reasons for the failure of your favorite began, often having little to do with reality, but the shape of the graphs could certainly have been influenced by the use of AMD Smart Access Memory or Resizable BAR. Some reviewers include such features, while others omit them as optional. Personally, I was in the second group so far, but as promised, I decided to check what the relationship between the cards would look like after turning on RBAR.

Author: Sebastian Oktaba

AMD Smart Access Memory and Resizable BAR it can hardly be called a revolution, because the mechanism used has long been part of the PCI-Express standard. However, it was only in recent months that it began to play a more important role. The first initiative came from AMD adding support to the Radeon RX 6000 family, then NVIDIA joined with the premiere of the GeForce RTX 3060 (older cards required a BIOS update), while Intel in the characteristics of its graphics systems directly communicates that it practically requires RBAR activation for proper operation. However, the principle of operation of both solutions is identical, so at least theoretically, the differences in performance should be marginal. The technology itself is about the possibility of expanding the base address register, where instead of the existing 256 MB blocks, the central processor receives access to the full VRAM capacity. This should dramatically reduce or completely eliminate the bottleneck in transferring data between components, as the CPU coordinates the work of the graphics chip.

Will the AMD Radeon RX 7900 XTX by enabling RBAR beat the NVIDIA GeForce RTX 4080? How much efficiency can be gained thanks to such a treatment?

To activate AMD Smart Access Memory or Resizable BAR, you must have a compatible hardware platform, where the minimum in the form of AMD Ryzen 3000 / Intel Core 10 GEN is specified by the manufacturers, but in fact there is a free American here. Ultimately, you just need to verify whether your set supports SAM / RBAR, which requires visiting UEFI and checking the appropriate tab, most often described as PCI Subsystem Settings. You may also need to update your motherboard’s BIOS and some older graphics cards. Then we set the Re-Size Bar to Enabled, save the changes and return to the operating system. Whether the function is enabled will be indicated by the software, e.g. CPU-Z. It should be remembered that SAM / RBAR techniques can increase the number of frames per second, although they do not always work correctly and bring the expected results. However, the balance of benefits is usually profitable, so it’s worth at least checking out the SAM / RBAR capabilities, especially if you occasionally play Forza Horizon 5, Horizon: Zero Dawn or Call of Duty: Modern Warfare II.

NVIDIA GeForce RTX 3090 Ti vs AMD Radeon RX 6950 XT – Performance AMD Smart Access Memory vs Resizable BAR

Returning to the NVIDIA GeForce RTX 4080 and AMD Radeon RX 7900 XTX tests – the premiere ones were made without activating Resizable BAR, while today’s ones include the above function. This will allow us to check whether AMD really manages to overtake the NVIDIA model in classic rasterization as well as ray tracing. At the same time, I already wanted to enter measurements with it turned on HAGS (Hardware Accelerated GPU Scheduling), a feature that is part of Windows 10/11, which can also slightly improve the number of frames per second. Unfortunately, although it was supported in older AMD drivers, it currently remains inactive and it’s hard to say when this will change. NVIDIA, in turn, supports HAGS each time, because it is needed to enable DLSS 3. Therefore, basic measurements do not include HAGS, while in DLSS 3 mode it will be temporarily turned on (note applies to measurements for the full procedure). I have vain hopes that any doubts about the results will be dispelled, and you can check the test site as always on the next page. The final countdown begins…