The CUDA engine is supported only in 64-bit builds of V-Ray RT for Fermi- and Kepler-based nVidia cards. It is recommended to use the CUDA engine on nVidia GPUs.
Rendering on multiple GPUs is supported and by default V-Ray RT for GPU will use all available OpenCL/CUDA devices. See the sections below how to choose devices to run V-Ray RT GPU on.
V-Ray RT for GPU has been tested on a number of graphics cards including:
nVidia GeForce 680 GTX;
nVidia GeForce 580 GTX;
nVidia GeForce 590 GTX;
nVidia GeForce 570;
nVidia GeForce 480 GTX;
nVidia Tesla C2050;
nVidia Quadro 2000M;