Nvidia has added SLI support specifically for Darkfall in their new beta drivers.
To get them go to
HERE and select 'beta' in the options, your graphics card, your OS and use the search option.
For Windows7 / Vista 32bit you can get them
HERE
Please note that these are beta drivers, however we've cooperated with Nvidia on this, and we've tested them in-house and they work for our configurations.
C&P from
HERE