Intel Core i7-6600U vs Intel Core i7-4940MX vs Intel Core i7-4558U

Intel Core i7-6600U

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.

Architecture

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").

Performance

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.

Graphics

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.

Power Consumption

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.

Intel Core i7-4940MX

The Intel Core i7-4940MX is a high-end quad-core processor for laptops and successor of the i7-4930MX. It is based on the Haswell architecture and was launched in Q1/2014. Due to Hyperthreading, the four cores can handle up to eight threads in parallel leading to better utilization of the CPU. Each core offers a base speed of 3.1 GHz but can dynamically increase clock rates with Turbo Boost up to 3.8 GHz (for 4 active cores), 3.9 GHz (for 2 active cores) and 4.0 GHz (for 1 active core). Furthermore, the Extreme CPUs offer an unlocked multiplicator for easy overclocking.

Architecture

Haswell is the successor to the Ivy Bridge architecture with improvements on both GPU and CPU performance. The CPUs are produced in 22nm and offer an optimized branch prediction as well as additional execution ports, increasing the performance per clock by about 5 - 10 percent. Furthermore, new features like AVX2 and FMA should increase the performance in future applications.

Performance

Compared to the Core i7-4930MX, the 4940MX is clocked just 100 MHz higher and therefore only slightly faster. Overall, the performance is similar to the Desktop Core i7-4770K. Even extremly demanding software or multitasking will be handled easily.

Graphics

The integrated Intel HD Graphics 4600 offers 20 Execution Units (EUs) clocked at 400 MHz up to 1350 MHz with Turbo Boost, making it about 30 % faster than the HD 4000. This is slightly slower than the AMD Radeon HD 8650G, but similar to a dedicated GeForce GT 720M.

Power Consumption

The i7-4940MX is rated at a TDP of 57 W including graphics card, memory controller and VRMs.  Therefore, the CPU is only suited for laptops 17-inches or greater.

Intel Core i7-4558U