NVIDIA formally brought its Kepler graphics core to the market Thursday, starting with its desktop line. The GeForce GTX 680 introduces new multiprocessing core groups known as SMX; they reportedly provide twice as much performance for the same energy as the GeForce 500 series. With three times as many cores as its ancestor (1,536), 2GB of 256-bit GDDR5 memory, and a 1GHz base clock, it's purportedly 43 percent faster in a game like Skyrim than AMD's Radeon HD 7970, even as it uses 28 percent less power.