The Mafia II engine passes physics handling over to the NVIDIA PhysX libraries and takes advantage to offer high physics settings which can be partially accellerated by the GeForces.
To measure performance we used the built-in benchmarks and all graphics options were pushed to a maximum, first without activating PhysX effects accelerated by the GPU:
The Radeon HD 6990 has the advantage here at 2560x1600 while the GeForce GTX 590 takes the lead at 1920x1200.
Next, we set all PhysX options to high:
With PhysX effects pushed to a maximum, performance levels dive. Note that they are in part limited by the CPU, as not all additional PhysX effects are accelerated. The Radeons are of course a long way behind.
Mafia II can detect when a large display area is made up of three monitors and registers them as 3 x 1920x1080 and not 5760x1080, which enables it to adapt the user interface automatically. For reasons unknown however, this detection system fails with a Radeon HD 6990 + Radeon HD 6970 pairing (triple CrossFire X) as well as with the Radeon HD 5970. The interface is then unusable and the rendering of the benchmark mode is only displayed on one screen.
On the GeForce side, activating antialiasing has no effect. We imagine that NVIDIA must have blocked the activation of antialiasing in its drivers to prevent the impact of lack of memory.
The GeForce GTX 590 steals a march on the GTX 580 when antialiasing is activated, but remains behind the GeForce GTX 570s in SLI.