Intel Core i7-3940XM vs Intel Core i7-7920HQ vs Intel Core i3-7100U

Intel Core i7-3940XM

The Intel Core i7-3940XM is the fastest quad-core processor for laptops (at the time of introduction in September 2012) an successor of the i7-3920XM. 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 3.0 GHz but can dynamically increase clock rates with Turbo Boost up to 3.7 GHz (for 4 active cores), 3.8 GHz (for 2 active cores) and 3.9 GHz (for 1 active core). Furthermore, the Extreme CPUs offer an unlocked multiplicator for easy overclocking.

Ivy Bridge is an enhanced die shrink of the Sandy Bridge architecture with improvements on both GPU and CPU performance. The CPUs are produced in 22nm (versus 32nm Sandy Bridge CPUs) and are the first to introduce 3D transistors for increased energy efficiency when compared to similarly clocked Sandy Bridge processors. Other new features are integrated PCI Express 3.0 and  DDR3(L)-1600 support.

The performance of the Core i7-3940XM should be slightly above a similarly clocked Sandy Bridge processor due to slight architectural improvements. Because of the higher clock speed, the former champion Core i7-3920XM should be outperformed by about 3%.

The integrated Intel HD Graphics 4000 offers 16 Execution Units (EUs) clocked at 650 MHz up to 1350 MHz with Turbo Boost, making it the fastest variant.

The XM CPUs are rated at a TDP of 55 Watts including graphics card and memory controller and therefore 10 Watt higher than the other quad-core models.  Therefore, the CPU is well-suited for laptops 17-inches or greater.

Intel Core i7-7920HQ

The Intel Core i7-7920HQ is a fast quad-core processor for notebooks based on the Kaby Lake architecture and was announced in January 2017. It is the top model of the consumer series at the time of the announcement. Only the Xeon E3-1535M v6 is faster (100 - 200 MHz higher Turbo clocks). Besides four cores including Hyper-Threading support running at 3.1-4.1 GHz (4 cores up to 3.7 GHz, 2 cores up to 3.9 GHz), the processor is also equipped with the HD Graphics 630 GPU as well as a dual-channel memory controller (DDR3L-1600/DDR4-2400). It is manufactured in a 14nm process with FinFET transistors.

Architecture

Intel basically uses the same micro architecture compared to Skylake, so the per-MHz performance does not differ. The manufacturer only reworked the Speed Shift technology for faster dynamic adjustments of voltages and clocks, and the improved 14nm process allows much higher frequencies combined with better efficiency than before.

Performance

The performance is a bit higher compared to the Skylake predecessor Core i7-6920HQ (2.9-3.8 GHz) thanks to slightly higher clocks (up to 7.9%), so it is the fastest mobile consumer processor in the beginning of 2017 (mobile Xeon E5-1535M v6 has even higher Turbo clocks). The performance is sufficient even for very demanding tasks and on par with powerful desktop quad-core processors.

Graphics

The integrated Intel HD Graphics 630 has 24 Execution Units (similar to previous HD Graphics 530) running at 350 - 1100 MHz. The performance depends a lot on the memory configuration; it should be comparable to a dedicated Nvidia GeForce 920M in combination with fast DDR4-2133 dual-channel memory.

Contrary to Skylake, Kaby Lake now supports hardware decoding for H.265/HEVC Main 10 with a 10-bit color depth as well as Google's VP9 codec. The dual-core Kaby Lake processors, which were announced in January, should also support HDCP 2.2.

Power Consumption

The chip is manufactured in an improved 14nm process with FinFET transistors, which improves the efficiency even further. Intel still specifies the TDP with 45 Watts, but it can also be reduced to 35 Watts by the notebook manufacturers (cTDP down). This will obviously affect the performance, because the Turbo Boost cannot be maintained for longer periods.

Intel Core i3-7100U

The Intel Core i3-7100U is a dual-core processor of the Kaby Lake architecture. It offers two CPU cores clocked at 2.4 GHz (without Turbo Boost) and integrates HyperThreading to work with up to 4 threads at once. The architectural differences are rather small compared to the Skylake generation, therefore the performance per MHz should be very similar. The SoC includes a dual channel DDR4 memory controller and Intel HD Graphics 620 graphics card (clocked at 300 - 1000 MHz). It is manufactured in an improved 14nm FinFET process at Intel. Compare to the old Skylake Core i3-6100U, the i3-7100U offers a 100 MHz improved clock speed.

 Architecture

Intel basically uses the same micro architecture compared to Skylake, so the per-MHz performance does not differ. The manufacturer only reworked the Speed Shift technology for faster dynamic adjustments of voltages and clocks, and the improved 14nm process allows much higher frequencies combined with better efficiency than before.