I was talking about a technique where deferred rendering, GPU is used in modern PS3 games to render surface normals, material index, Z-buffer, texture color, etc. in a buffer. Typically 128 bits per pixel.

This buffer is then DMA transferred to SPUs, where final lighting and fragment shading is performed.

Final step is to transfer 32-bit RGB data back to GPU's frame buffer for displaying.

Here's a link about one implementation: http://www.slideshare.net/DICEStudio/spubased-deferred-shadi...