Quick comment on the tile stuff: Apple GPUs basically rasterize primitives into small tiles (16x16 or 32x32 pixels), tracking primitive coverage and barycentric

Quick comment on the tile stuff: Apple GPUs basically rasterize primitives into small tiles (16x16 or 32x32 pixels), tracking primitive coverage and barycentric coordinates per pixel. Once all primitives are rasterized, the entire tile is shaded at once. That’s where the “deferred” in tile-based deferred shading comes from. This helps to utilize both the compute hardware and memory subsystem more efficiently. Tile data is stored in the very fast on-chip shared memory (essentially large programmable register file). Apple also exposes this abstraction to the user, allowing them to freely manipulate the contents of this memory and persist it through multiple kernel invocations. Using tile memory explicitly can radically simplify some rendering algorithms, improve performance efficiency and reduce the RAM bandwidth needs. Since the concept tiles are so important to Apple GPUs, they also support bulk memory moves which allow one to push the contents of the entire tile (multiple KBs) in one operation, which is obviously more efficient than doing scattered writes. So it’s exactly as you say: of course one can improve performance by using these features, but it’s not that one has to do it to get good performance in the first place. If there are performance issues with the Ultra, memory hierarchy is an unlikely culprit IMO.