I’m fairly new to Blender. I just upgraded from a laptop to a desktop with dual 6 core Xeon processors and dual K4200 NVIDIA graphics cards. Will Blender automatically use both processors for rendering or do I need to change a setting? Is it faster to use the CPU or GPU rendering?
Blender should automatically pick up on all available CPU cores. Whether GPU is faster is heavily dependent on scene and materials, and whether or not the scene can even fit into vRAM. Depending on the Xeon model, there’s a good chance your CPU setup will be substantially faster than the GPUs.