Intel Core i7-3517U vs Intel Core i7-7660U vs Intel Core i7-7700HQ

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.

Intel Core i7-7660U

The Intel Core i7-7660U is a fast dual-core SoC for notebooks and Ultrabooks based on the Kaby Lake architecture and was announced in January 2017. The CPU has two processor cores clocked at 2.5-4 GHz (two cores up to 3.8 GHz). The processor can execute up to four threads simultaneously thanks to Hyper Threading. It is also equipped with an Intel Iris Plus Graphics 640 GPU with 64 MB eDRAm, a dual-channel memory controller (DDR4) as well as VP9 and H.265 video decoding as well as encoding. The chip is still manufactured in a 14nm process with FinFET transistors.

Compared to the Core i7-7600U, the 7660 does have a higher single-core Turbo of 4 GHz (+100 MHz), but a lower dual-core Turbo (-100 MHz) and a lower base frequency (-300 MHz). However, the CPU part can also use the 64 MB eDRAM as L5 cache.

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

At 2.5-4 GHz, the Core i7-7660U has a slightly lower frequency (except for the single-core Turbo) compared to the Core i7-7600U, but the CPU part can also use the 64 MB eDRAM, so the performance should be similar.

Graphics

The integrated Intel Iris Plus 640 Graphics is the GT3e model of the Kaby Lake GPU (Intel Gen. 9.5). It has 48 Execution Units running at 300-1050 MHz and the performance is comparable to a GeForce 920MX thanks to fast eDRAM cache. However, there aren't any significant improvements compared to the old Iris Pro 540, so modern games can often not be played smoothly or only at the lowest or medium settings, respectively.

Contrary to Skylake, Kaby lake now also supports H.265/HEVC Main 10 with a 10-bit color depth as well as Google's VP9 codec. The dual-core Kaby Lake processors 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 15 Watts, which is typical for ULV chips. Depending on the usage scenario, the TDP can vary between 7.5 (cTDP Down) and 25 Watts.

Intel Core i7-7700HQ

The Intel Core i7-7700HQ is a fast quad-core processor for notebooks based on the Kaby Lake H architecture (7th generation Core), which was announced in January 2017 at CES. It is the successor to the Core i7-6700HQ from the Skylake generation and is manufactured in an improved 14 nm+ process, so the clocks are 200 MHz higher at the same TDP. The architecture was not changed, only the video engine got an update (see our Kaby Lake article).

The integrated graphics card is called Intel HD Graphics 630, but the architecture does not differ from the 530 GPU from the Skylake generation and only the clocks are slightly higher. 

Performance

Thanks to the 200 MHz higher clocks (5.5-7.6% depending on the Boost), the CPU performance is increased and roughly on par with the Core i7-6970HQ (2.8-3.7 GHz but with 128 MB eDRAM). The TDP can also be reduced to 35 Watts (cTDP down), but this will reduce the performance.

Power Consumption

Due to its 45-Watt TDP, the CPU will be used in bigger notebooks with at least 15 inches most of the time.