So the early reports claim that GTX 1080 is about 25% (1.25) faster compared to Titan X in game performance. This is achieved however with 2560 CUDA cores, compared to the 3072 CUDA cores of the Titan X, or with 20% (1.2) less. Overall, this gives 50% (1.2 x 1.25) better performance in game performance.
However 1080 runs at 1.6GHZ base clock, which is >50% more compared to the ~1GHZ for the Titan X.
In the best case scenario, we have 0 (zero) improvement in game performance per clock in Pascal compared to Maxwell.
But 1080 (GP104) gets exactly the same game performance per clock as Titan X (GM200) for 180W, compared to the 250W of the Titan X, which is ~40% improvement. Meaning, that most likely the Pascal architecture is exactly as efficient as Maxwell for games and that this 40% improvement are coming from the new 16nm FinFet process (the lower price comes as a bonus).
I expect there to be some (or a lot) of improvement per clock for GPGPU apps, mainly because of the doubled amount of registers – 32k vs 16k (game shaders care about those register far less compared to the GPGPU apps) and the native 16bit floating point number support. Pascal has a number of other GPGPU specific features, like: compute preemption, which allows using of GPGPU apps with 1 GPU without the OS UI becoming sluggish; shared virtual memory with the CPU; nvlink which should allow stacking of the GPU memory frame buffers (so 2 GPUs with 16GB memory each will give 32GB of usable memory); more shared memory. All of these take a lot of transistors to make and don’t really contribute to gaming. Finally after Kepler and Maxwell, it seems like NVidia are focusing not only in games …
Good thing is that it seems that AMD Polaris should be better suited compared to the current GCN architecture as well. It will have new L2 Cache (critical for GPGPU) and new memory controller. On top of that it seems to have new dynamic instruction scheduler, which happens to help a lot of the complex GPGPU apps (this was last seen in the nVidia Fermi GPUs, which probably was one of the reasons the Fermi cores were that powerful). AMD will most likely go for performance per watt, and not necessarily the highest performance (so the Polaris GPUs will be relatively small).
All we have to do is wait and see if all of this will actually work …
p.s. check the follow up of this post here.