Games tend to be more and more glorious when it comes to visual attraction. There is a tremendous difference in quality of the GLQuake released a decade ago with the Half-Life 2: Lost Coast released months back. It is not a secret that pixel shaders significantly simplify development of modern games and it is obvious that next-generation titles will only have more of them. A question for hardware developers is what will the next-generation pixel shaders look like. Particularly, it is completely clear that pixel shaders will tend to be more math1ematically intensive, as we mentioned above, but what remains unknown, is the ratio between arithmetic and texture operations required by future titles.
In fact, we still do not know the demands of even current games: the developers are tight-lipped over the technologies they use to create effects. We have seen very few software suites that can actually determine the bottlenecks of the current games – one is ATI’s plugin for Microsoft’s PIX , another one is Nvidia’s PerformanceHud . A problem with launching such suites is that game developers protect their titles from being analyzed by such software by third parties. That said, we have to believe what hardware developers are reporting about requirements of modern games based on claims allegedly made by game developers.
ATI claims that even current games like F.E.A.R. requires a GPU to perform up to 7 arithmetic operations on one texture operation, whereas the ratio for the Splinter Cell: Chaos Theory is 8 arithmetic operations on 1 texture operation. Keeping this in mind, ATI’s latest graphics processors – Radeon X1600- and Radeon X1900-series – feature three times more pixel shader processors compared to texture address units. The company believes that 3:1 ratio of arithmetic to texture units provides the ideal balance for current and future 3D performance.
While generally ATI’s approach seems to be correct since the company has to consider transistor count and die size for its chips, texture fetch performance and bandwidth are still crucial for the graphics processors. For instance, when creating a realistic material, a pixel shader has to do a number of lookups to large textures, which means that performance limitations will come from both insufficient number of texture address units and/or insufficient memory bandwidth. While game developers have chances to reduce the demand of their titles for high memory bandwidth and texture operations by using more pixel shaders to create certain effects, they seem to have been reluctant in doing so for a while as there are a lot of graphics processors for which high math1ematical load may mean significant performance degradation; hence, ATI’s new chips won’t necessarily become the winners across the board just now.
However, when games will acquire math1ematically intensive effects, such as parallax occlusion mapping and others, when the main performance limiter will be pixel shader performance, the new approach to design a GPU is likely to show its advantages.