Power, Temperature, Noise
There's always an energy price to pay for excellent performance. A second card adds just over 200W to our system-wide figure.
The extra noise generated by a second card depends on how good the chassis airflow is and how the cards are positioned. We noted a single card's fan would increase to around 2,400rpm after 10 minutes of gaming. The second, SLI-forming card's fan jumps up to 2,900rpm while the first runs only marginally slower.
Want a very quiet experience with two-card Titan X? It's best to opt for something along the lines of the EVGA Hydro Copper.