By this i take it you are talking about the rendering modes, well what i know about it there are 4 for nVidia and like 8 for ATI, thus this ATI/AMD fanboi concludes ATI>>>AMD sorry i dont use SLI/CF so i am not to familiar with the rendering modes but search google for SLI rendering modes or summin.
oh you want just more frame rates
open the nvidia control panel set all the driver settings to default and disable vertical sync in games
download fraps from guru3d and give it a try before and after
btw i read an article which says if you have a SLI mobo and you have installed just one card and you enable the sli option in the nvidia control panel ...well you should see an improvment in fps....well i have to verify this myself 8O
Split frame rendering is where each card works at the same time. For every frame, 1 card does the upper half, and the other card generates the lower half of your screen. The other modes are when you force your main card to produce every even numbered frame, and the slave card does every odd numbered frame, or vice versa, im not sure what single gpu is there for???????????
i did a liitle bit of research
here we go
according to nvidia SLI Frame Rendering: Combines two PCI Express graphics cards with an SLI connector to transparently scale application performance on a single display by presenting them as a single graphics card to the operating system. here
you can find more info Alternate Frame Rendering Alternate Frame Rendering 2
that's it for now i did not sleep all night tommorow i will post more info 'yawning'