Intel Core i7-3940XM vs Intel Celeron 3965Y vs Intel Core i7-3517U

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 Celeron 3965Y

The Intel Celeron 3965Y is a low power entry level processor for small laptops or tablets and based on the Kaby Lake architecture. It was announced in Q2 2017 and offers two processor cores clocked at 1.5 GHz (no Turbo Boost). Compared to the Pentium 4410Y, the Celeron 3965Y offers no HyperThreading and therefore can execute only up to two threads simultaneously. The chips also includes the Intel HD Graphics 615 GPU, a dual-channel memory controller (DDR3L/LPDDR3) as well as VP9 and H.265 video de- and encoder. It is still produced in a 14 nm process with FinFET transistors. Currently (2017) it is the slowest Kaby-Lake based processor.

Architecture

Intel basically used the familiar micro architecture from the Skylake generation, so the per-MHz performance is identical. Only the Speed-Shift technology for faster dynamic adjustments of the voltages and clocks was improved, and the matured 14 nm process now also enables much higher frequencies and better efficiency than before. 

Performance

Due to the missing HyperThreading, the Celeron 3965Y is slightly slower than the similar clocked Pentium 4410Y in some multi threaded benchmarks. The single thread performance is due to the missing Turbo Boost significantly worse than the more expensive Core m3-7Y30. This should be noticeable in daily tasks. 

Graphics

The integrated Intel HD Graphics 615 GPU has 24 Execution Units (EUs) like the old HD Graphics 515 and runs with clocks between 300 and 850 MHz in combination with this processor. The performance heavily depends on the TDP limit as well as the memory configuration; with fast LPDDR3-1866 RAM in dual-channel mode, the GPU should sometimes be able to compete with the HD Graphics 520, but can also be much slower in other scenarios. Modern games from 2016 will, if at all, only run smoothly in the lowest settings.

Contrary to Skylake, Kaby Lake now also supports hardware decoding for H.265/HEVC Main10 with a 10-bit color depth as well as Google's VP9 codec.

Power Consumption

The chip is manufactured in an improved 14 nm process with FinFET transistors, so the power efficiency was once again improved significantly. The TDP is rated at 6 Watt and can be reduced to 4,5 Watt (cTDP down).

Intel Core i7-3517U

The Intel Core i7-3517U is a fast ULV-processor for laptops based on the Ivy Bridge architecture released in Q2 2012. Due to Hyperthreading, the two cores can handle up to four threads in parallel leading to better utilization of the CPU. Each core offers a base speed of 1.9 GHz but can dynamically increase clock rates with Turbo Boost up to 2.8 GHz (for 2 active cores) and 3.0 GHz (for 1 active core). As its Sandy-Bridge-based predecessors, it offers a 4 MB L3-Cache.

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 i7-3517U is slightly above a similarly clocked Sandy Bridge processor due to the architectural improvements. Therefore, and because of the higher clock speed, the older Core i7-2677M is easily outperformed.

The integrated Intel HD Graphics 4000 offers 16 Execution Units (EUs) clocked at 350 MHz up to 1150 MHz with Turbo Boost, delivering a performance comparable with an AMD Radeon HD 6620G.

The ULV-CPUs are rated at a TDP of 17 W including graphics card and memory controller.  Therefore, the CPU is suited for small laptops and ultrabooks.