Ok and the results are in for single and SLI after i finally managed to get a custom SLI profile to work!
All setting at 1920x1200
2 graphics settings tested
1. Everything high settings and 4xAA with all checkboxes selected vsync off (almost maxed out)
2. Maxed out settings with 4xAA with all checkboxes selected vsync off
Firstly what I noticed.
The GTX580 in both single and SLI is way smoother than my old setup. (for dual SLI only - see notes below)
Only graphical anomaly was in SLI mode with ocassional slight shadow flicker from smoke and very small frame jitter. MUCH SMOOTHER! Likely some more fiddling with more custom settings in SLI profile would all but remove this. An official driver profile from nvidia is the best bet.
Final Performance Notes...
There is currently no benefit with current driver SLI support and game optimisation going further than a 2 card SLI setup with GTX 580.
You get a very minor max increase for TRI SLI and slightly negative scaling for AVG FPS.
Negative scaling for QUAD SLI on both AVG and MAX.
You need mega power supplies for QUAD SLI!
Nvidia 580 has the edge for less big stutters and pauses compared to the ATI 5870 in SLI/Xfire but Nvidia has a noticeable microstutter and surging with anything above 2 card SLI. Compared with the ATI 5870s which have some bigger hiccups and pauses but they are generally smoother.
Nvidia is quicker to settle with scene changes when changing internal and external views with very minimal texture draw delay and stutter.
5870 QuadFire seems to scale a little bit better in terms of MAX and AVG FPS compared to NV QUAD SLI... with the caveats below...
Overall both SLI and Xfire are not officially working and both required work arounds which are not optimal so there will be further hope for future driver profiles and game optimisation.
Image Quality Notes
Anti Aliasing looks better on NVIDIA but not for everything. Mind you I was using standard driver settings so it might be possible to tweak AA quality a bit.
Final conclusion...
A dual SLI GTX580 setup would appear to be the optimal smoothness and performance with current drivers and game code at 1920x1200 res.
OK some stats and pics
Single 580 on high
avg 52
max 98
min 14
SLI 580 on high
avg 64
max 152
min 6
TRI SLI 580 on high
avg 60
max 146
min 9
QUAD SLI 580 on high
avg 55
max 142
min 12
Single 580 Vhigh (Maxed)
avg 48
max 94
min 5
SLI 580 Vhigh (Maxed)
avg 58
max 144
min 18
TRI SLI 580 Vhigh (Maxed)
avg 56
max 139
min 9
QUAD SLI 580 Vhigh (Maxed)
avg 50
max 134
min 8
Single 580 High
Single 580 Vhigh (Maxed)
SLI 580 High
SLI 580 Vhigh
TRI SLI High
TRI SLI Vhigh
Quad SLI High
Quad SLI Vhigh
