PowerVR

1. The PowerVR chipset uses a method of 3D rendering known as tile-based deferred rendering.
2. Rays are cast onto the triangles associated with the tile and a pixel. PowerVR hardware typically calculates the depths associated with each polygon for one tile row in 1 cycle.
3. Unlike a more traditional z-buffered rendering pipeline, no calculations need to be made to determine obscured.
4. Allows for correct rendering of partially transparent polygons, independent of the order.(It is generally not included for lack of API support and cost reasons)
5. As the rendering is limited to one tile at a time, the whole tile can be in fast onchip memory, which is flushed to video memory before processing the next tile.

         http://en.wikipedia.org/wiki/PowerVR