It seems that I'm getting the same performance whether I use 1 card or both.
 
The benchmarks are almost identical (within +/- 2 fps average) if I have one card physically installed or both installed.
 
1x GTX 470 is good for about 55 fps (1920x1200, 16xAF, no AA, max detail, no physx, no vsync)
If I bump up the physx to high I get about 22 fps) . I thought one of the cards may be bad, but I tried each one indvidually, and they benchmarked about the same.
 
With 2x GTX470's performance is identical. Even if i dedicate one to physx duty there is no meaningful improvement. If I have both in SLI, again there is no real improvement.
 
I've tried a couple things so far. I unistalled the Nvdia/Physix drivers, ran a driver cleaner, reinstalled the lasted Nvidia drivers and the latest Physx driver. I also ran the latest EVGA SLI enhancements, but nothing has helped. My PC isn't a spring chicken anymore, but I was hoping for bit better performance, since I've seen benchmarks of people with similar setups getting better results. Any ideas on why the game is running so slowly for me? Specs are as follows:
 
CPU :  Intel Q6700 @3.2 Ghz
Mobo: EVGA 680i LT SLI
RAM :  8GB Corsair Dominator 1066
GPU :  2x EVGA GTX 470 in SLI
HDD:  2x 500 GB Seagate 7200 RPM SATA
PSU:  850 watt Thermaltake Toughpower
Monitor: Dell Ultrasharp 2408 24 inch
OS: Windows 7 Pro 64 bit
 

kram36

55 fps with an old mobo, memory and cpu you have and you call it lacking?

Well, yeah. I've seen people with significantly slower rigs post better benchmarks. I'm mainly concerned about the fact that the pressence of a dedicated 470 as a physx card seemed to make no difference at all vs. running the game with a single card with the physx set at high.  Yes my CPU and mobo are old, but I think I should be doing better than a rig with a dual core Athlon and single 5870.

be lucky that you're able to play it with that system. i get 50fps with 1 480 SC w/ physx enable or around 95-100fps with no AA and physx off. (1920x1080 res).

u need faster CPU, its a bottleneck for 1 GPU let alone 2 in SLI.

Q6700..  Sorry nothing personal but that chip is a real dog.  If you wanted to go cheap, step up to a Yorkfield. That would give you better performance without investing in a i7 platform. 

But yea, i7 brings whole lot to the table in everything...it was a game changer at the time it was released (almost two years ago now...man how time flies!)

If you are in the market for an i7, the 950 model just dropped down to $300. A helluvalot better than the 600+ they were asking before.