Video cards also have their own memory, separate from the main computer memory. It is usually much faster than main computer memory, too. This helps the GPU do its graphics calculations even faster. Most video cards also can make one computer use more than one computer monitor at one time. Graphics manufacturers Nvidia and AMD (Advanced Micro Devices) have special technologies that allow two identical cards to be linked together in a single computer for much faster performance. Nvidia calls their technology and AMD calls their technology . Some modern graphics cards can even process physics calculations to create even more realistic-looking 3D worlds.