A leak from Kepler_L2 on X has provided new details about the changes AMD is planning for its upcoming RDNA 4 GPU architecture, specifically in relation to ray tracing. While some of the updates hint at significant improvements in certain aspects of the algorithms, the leak also suggests that there may not be a complete overhaul of the ray tracing units as a whole.
‘Double Intersect Ray Tracing Engine’ Update
One key update highlighted in the leak is the introduction of a ‘Double Intersect Ray Tracing Engine.’ This could mean that AMD’s RT units in RDNA 4 will either be doubled in number compared to RDNA 3, or they may simply be capable of processing twice as many ray-triangle intersection calculations. The ultimate goal is to enhance ray tracing performance, which is currently lagging behind Nvidia’s RTX 40-series GPUs.
Beyond ray-triangle intersection calculations, the time-consuming traversal through BVH acceleration structures also plays a crucial role in ray tracing performance. AMD is reportedly working on optimizations in this area to improve efficiency, although the details remain unclear. Notably, there is no mention of AMD utilizing ASIC technology to accelerate BVH traversals, which could potentially impact the overall performance.
Potential Challenges with Compute Shaders
In RDNA 2 and 3, BVH traversal is handled through compute shaders running on the GPU’s cores. This can pose limitations as the compute shaders may occupy the GPU’s resources, preventing them from being used for other tasks, such as ray shaders. While this is less of a concern for larger Navi GPUs with plenty of Compute Units, it becomes more noticeable in lower-tier models lacking dedicated traversal units.
Nvidia’s ray tracing units feature independent ray-triangle intersection engines and BVH traversal circuits, leading to superior performance in ray tracing tasks. It remains to be seen whether AMD will introduce similar dedicated traversal units in RDNA 4, as this could potentially address the performance gap between AMD and Nvidia GPUs in ray tracing capabilities.
The leak suggests that most of the RT updates will be utilized in the upcoming PlayStation 5 Pro, with rumors circulating about potential support for BVH8 traversal shaders. This could indicate a significant improvement over RDNA 3, although the actual impact on gaming performance remains to be determined.
As ray tracing becomes a standard feature in modern GPUs, it is crucial for AMD to stay competitive with Intel and Nvidia, both of which are expected to release their next-generation GPUs around the same time as RDNA 4. With Nvidia’s fourth iteration of RTX technology on the horizon, AMD will need to offer something innovative and competitive to establish its GPUs as viable alternatives in the market.
AMD’s updates for ray tracing in the RDNA 4 GPU architecture show promise but also raise questions about the extent of the improvements and how they will impact overall performance. As the industry continues to embrace ray tracing technology, it is essential for AMD to deliver a compelling and efficient solution to remain competitive in the GPU market.
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