Nvidia Quadro Workstation User Manual page 184

Chapter 9
Using NVIDIA Scalable Link Interface (SLI)
5 Check Enable SLI multi-GPU.
6 Click the Select display list arrow, then click the display that you want to use as
the SLI display.
7 Click OK.
You can now configure your system to use SLI, as explained in the next section.
172 Quadro Workstation User's Guide