This brings us to speed. Most of what systems can handle is limited by the types of rendering and the total number of objects a particular scene can support before a slideshow ensues. AFR is one way to maximize the total number of frames the graphics subsystem can push out. 3Dfx's Scan Line Interleave was a first step into this direction; the first line of the frame is rendered by the first core and the second is rendered by the second and so on. Quad SLI takes this to the next level.
The fastest way Quad SLI can render frames is by having every fourth frame rendered by a single GPU. This mode is called 4-way AFR. The first frame to be rendered is managed by the first GPU (GPU0 in the diagram below) while the next is rendered by the second and so on.
A hybrid of image quality and speed is what is referred to as "AFR of SFR". The first two GPUs work on the odd frames (1,3,5,...) and the even frames are rendered by the second set of GPUs.