when aer fragments groupped per tile

from PowerVR Series5 Graphics.SGX architecture guide for developers.1.0.8.External,

“the TSP can submit groups of visible fragments to the USSE via the CGS to be textured and shaded (visible fragments are grouped by the ISP during the HSR process)”, while “the ISP submits fragments to the TSP in groups of fragments that belong to the same primitive”. So the result of TSP is that fragments are grouped per primitive.

“During the rasterization, texturing and shading process, each additional graphics core allows another tile to be processed in parallel. To enable this, the hardware manages a queue of all tiles that need to be processed and each graphics core fetches and processes a tile from this queue.”, at this time, the fragments are grouped per tile.

So, my question is when are the fragments grouped from per primitive to per tile, thanks.

Please see this topic for more information

The ISP is the unit that takes the geometry and tiling information from the parameter buffer and actually determines which fragments must be processed per tile. As the document says, these are grouped together by primitive to help with the efficiency of their processing.