I have been using SLI for a long time now but its supposed to be broken with not only AHII but FSX also. NickN of the UTX utility for FSX wrote a configuration writeup on FSX to lay to rest what works and what doesnt. I was reading through that when I found that he thinks Nhancer is absolutely required for a card (Nvidia) to control antialiasing in FSX for example. I knew the opposite to be true in AHII so I set about experimenting for myself. When the recent series of patches and updates came out for AHII I discovered that setting everything to application controlled was the best way to work with my setup but then I got to wondering why I was using SLI at all! I mean it doesnt make sense that Nvidia would create SLI if it doesnt do anything because return customers would be nonexistent. So I wanted to find out how to make things work for the best.
FSX details include UTX (USA Canada and Europe all options active) and Ground Environment X and Active Sky Advanced (w/ X Graphics textures) over 500 airliners from WOAI all sliders set to max (except ground traffic which is 8%) and all aircraft shadows on at 1920x1200x32 bit. I have airlines and standard textures on one drive and photo-terrain on another (I sometimes use TileProxy also).
I started with FSX by setting the card to application controlled on everything and setting FSX for best appearance. Second I decided to try something new and go with 'Enhance the application setting' for Antialiasing mode whereas normally this was set to Application controlled. Next I set antialiasing to a minimal setting like 4x and noticed not much improvement but I wanted to see how far the card (in this case 8800GTs) could go. To my surprise the higher I moved antialiasing the higher the frame rate went (bear in mind FPS improvements in FSX are counted in single digits). Finally I ended up with SLI 32x and the highest frame rates I have ever had. In the end I think this 'Enhance the application setting' approach is the best way to go (also use Nvidia recommended (SLI) for performance mode) and make sure to set Texture filtering - Negative LOD bias to 'Clamp.'
When I set AHII to the exact same settings all video flashes and shimmering terrain and stutters disappeared. Now I have moved to the 295s and I have all AHII settings at maximum (textures and shadows) and frame rates remain at 59 and 60 (refresh rate).
I would like to have anyone else with an SLI setup try the same thing and report back their findings. I hope things improve as much for you as they did for me.
