Intel’s Additional DirectX Extensions for Haswell
Currently Intel's integrated graphics are synonymous with minimal available performance, competing with lowest-end dedicated GPUs. However, it seems that Intel wants to get to the point, where their iGPUs will be more competitive. At GDC 2013 Intel has announced the features supported by iGPUs inside Haswell CPUs, including DirectX 11.1 and two new Intel-exclusive DirectX extensions – Instant Access and PixelSync. Intel has revealed that GRID 2 and Rome 2 will both support these new extensions.
Instant Access is Intel's approach to sharing CPU and GPU memory (similar to AMD's HSA). With it CPU can directly access memory used by GPU and vice-versa. This should allow avoiding many performance drops, associated with treating iGPU the same way as dedicated GPU further away from CPU.
PixelSync is more interesting of two when it comes to game graphics. Order Independent Transparency (OIT) is the rendering technology for correctly drawing transparent objects, even in cases when they intersect. DirectX 11 allows implementing OIT, but such implementations are quite heavy on memory and memory bandwidth. Intel's hardware solution uses some clever tricks to reduce the memory requirement, while using OIT, without sacrificing too much accuracy. With PixelSync, enabling OIT in games running on Haswell's iGPU reduces performance by 10%.
Overall, the performance improvements of Intel's integrated graphics are good news, considering its prevalence among Steam users. It will also help a lot for lighter laptops capable of gaming and gaming on x86 tablets.