The Intel Core i7-6600U is an ULV (ultra low voltage) dual-core SoC based on the Skylake architecture. In September 2015, it's the fastest CPU of the 15 W series, which can be found in ultrabooks as well as normal notebooks. In addition to two CPU cores with Hyper-Threading clocked at 2.6 - 3.4 GHz (2 cores: max. 3.2 GHz), the chip also integrates an HD Graphics 520 GPU and a dual-channel DDR4-2133/DDR3L-1600 memory controller. The SoC is manufactured using a 14 nm process with FinFET transistors.
Skylake replaces both Haswell and Broadwell and brings the same microarchitecture in every TDP class from 4.5 to 45 W. The extensive improvements of the Skylake design include increased out-of-order buffers, optimized prefetching and branch prediction as well as additional performance gains through Hyper-Threading. Overall, however, performance per clock has been increased by only 5 to 10 percent (compared to Haswell) respectively under 5 percent (compard to Broadwell), which is quite modest for a new architecture ("Tock").
According to the specified clock rates and the improved architecture, the Core i7-6600U should perform similar to a Core i5-4310M (Haswell, 37 W) and is one of the fastest ULV dual-cores as of late 2015. Thus, the CPU has sufficient power for office and multimedia purposes as well as more demanding applications and multitasking.
The integrated graphics unit called HD Graphics 520 represents the "GT2" version of the Skylake GPU (Intel Gen. 9). The 24 Execution Units, also called EUs, are clocked at 300 - 1050 MHz and offer a performance somewhere in range of a dedicated GeForce 820M. Games of 2015 can thus be played smoothly in low settings. For more information about performance and features, check our page for the HD Graphics 520.
Specified at a TDP of 15 W (including CPU, GPU and memory controller), the CPU is best suited for small notebooks and ultrabooks (11-inches and above). Optionally, the TDP can be lowered to 7.5 watts (cTDP down), reducing both heat dissipation and performance and allowing even more compact designs.