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The Tegra K1 comes in two pin-compatible configurations. In addition to the Denver-based duallie, there's a quad-core version based on ARM Cortex-A15 cores similar to those used in the Tegra 4. That second chip is limited to 32-bit applications, and its CPU cores will only scale up to 2.3GHz.
Based on Nvidia's die shots, two Denver cores appear to have the same silicon footprint as four Cortex-A15s. It will be interesting to see how the two implementations compare.
At the very least, both chips should have plenty of graphics horsepower. The Tegra K1's DirectX 11-class integrated graphics has 192 shader processors based on the Kepler microarchitecture. In Nvidia's desktop and notebook GPUs, each Kepler SMX unit also has 192 shader processors. The low-end GeForce GT 640 includes two SMXes, while the high-end GeForce GTX 780 Ti has 15 of them.