SLI: a joke?

Hi

I have the Europeian model of Toshiba X200 sli, and i have tryed different games with sli on and off, and with sli enabled the frames is much higher, but with most games like crysis the game stutter then i have around 20 frames sec with sli enabled and with sli off the game run much smother with 20 frames second, and the same is for MS flightsim x, and word in conflict. I realy dont see any benefit with sli enabled, exept higher framerate, but as i say, with sli games stutter with framerate like 15-20 and with sli off they dont

Could someone give me a (very) good explanation?

Sorry for my bad english

 

Different games Run better in different modes of SLi settings
From wiki -
# Split Frame Rendering (SFR), the first rendering method. This analyzes the rendered image in order to split the workload 50/50 between the two GPUs. To do this, the frame is split horizontally in varying ratios depending on geometry. For example, in a scene where the top half of the frame is mostly empty sky, the dividing line will lower, balancing geometry workload between the two GPUs. This method does not scale geometry or work as well as AFR, however.
# Alternate Frame Rendering (AFR), the second rendering method. Here, each GPU renders entire frames in sequence – one GPU processes even frames, and the second processes odd frames, one after the other. When the slave card finishes work on a frame (or part of a frame) the results are sent via the SLI bridge to the master card, which then outputs the completed frames. Ideally, this would result in the rendering time being cut in half, and thus performance from the video cards would double. In their advertising, Nvidia claims up to 1.9x the performance of one card with the dual-card setup.

I think Crysis is supposed to work better in Alternate Frame mode?

 

Many thanks for you reply TonyZ

THAT was a good explanation

Could i enable Alternate frame rendering in crysis?

 

I dont think you can IN Crysis, but you can right click on the Desktop (in Vista) and open up Nvidia Control Panel and set it from there.

In 3D settings goto 'manage 3D settings'

It will now show Global settings and a Program Settings TAB

goto Program Settings and find Crysis in the games list.

scroll down to SLi performance mode in the second list and select Alternate Frame rendering
I'm not too sure if its 1 or 2, but you could try both

 

Again many many thanks Tonyz

I would try this then i come back from work

 

The best setting for the games i have tried (Crysis, Bioshock, World in Conflict, Need For Speed ProStreet, UT3, Timeshift, FIFA 08, NBA LIVE 08, etc...) is Alternate Frame Rendering 2... With that i always get around 60~80 % more perfomance than with split frame rendering or AFR 1...
Use it and you will see the real gain of SLI...

BTW remember to change the setting for EACH GAME INDIVIDUALLY because nvidia, almost always, set as default the split frame rendering or even one gpu for most games...