2D Dual-Rate Texturing in D-Series GPUs

By _Imagination Blog

August 26, 2024

For every GPU generation the performance teams within Imagination run through a wide range of content, analysing and understanding the different workload types and their bottlenecks. As part of this analysis, the data revealed that many modern games spend an increasing amount of time executing post-processing algorithms to enable depth of field, bloom, blur and other effects.

Most of these post-processing passes are texture-sampling heavy filter effects which are modest in ALU requirements but bottlenecked by the throughput rate of the Texture Processing Unit (TPU). One approach to resolve this would be to simply brute force change the ratio of the number of TPU units versus the USC/ALU rate. However, our analysis indicated this was not a good strategy, for several reasons.

First, in regular render passes the ratio of ALU versus TPU in D-Series GPUs was already optimal and adding another TPU would simply not result in any benefits as the workload would become ALU limited. Meanwhile, other processing passes were TPU-heavy but also bandwidth-heavy, and hence boosting the TPU would not help, as there would be insufficient bandwidth to feed the extra TPU throughput so performance would not be enhanced.

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