Intel Core i5-8400 vs Intel Core i7-8650U

Intel Core i5-8400

The Intel Core i5-8400 is a mid-range 6-core CPU. The processor belongs to the Coffee Lake generation and was presented in September 2017. It does not support Hyper-Threading, which means it can run six threads simultaneously. The base clock rate is 2.8 GHz and the CPU can speed up to 4.0 GHz under high load. Despite belonging to the new generation of CPUs, the Core i5-8400 is manufactured in an improved 14nm process.

Performance

The processor offers a strong performance increase compared to the Core i5-7400 due to its two additional cores. Single-core performance has not improved significantly compared to its Kaby Lake predecessor. As a mid-range model, the Core i5-8400 should be suitable for demanding games and programs.

Graphics

The integrated Intel UHD Graphics 630 iGPU is supposed to offer higher performance as its clock rate has been increased by 50 MHz. The build is identical to that of the Intel HD Graphics 630. We do expect a performance improvement, but as a low-end solution it will probably only display current games smoothly at reduced details - if at all.

Power Consumption

Intel specifies the TDP with 65 watts. Therefore, well-dimensioned cooling systems should easily manage to deal with the created heat. We expect increased efficiency due to the higher performance.

Intel Core i7-8650U

The Intel Core i7-8650U is a power efficient quad-core SoC for notebooks and Ultrabooks based on the Kaby Lake Refresh generation and was announced in August 2017. Contrary to its direct predecessor the Core i7-7600U, which were still dual-cores, the i7-8650U is equipped with four cores but at a lower base frequency of 1.9 GHz. The Turbo Boost can go up to 4,2 GHz and therefore also offer good short term single core speeds. The GPU is now named Intel UHD Graphics 620 but otherwise identical to the Intel HD Graphics 620. The integrated memory controller supports DDR4-2400 / LPDDR3-2133 and dual channel memory.

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

According to Intel, the new quad core models are up to 40% faster than their dual core predecessors. Due to the reduced TDP and the same 14nm+ process, the long term performance and throttling behaviour will be interesting and depending on the laptop design. Therefore, the older 35 Watt quad-core models should be faster in applications that demand longer CPU loads. The performance however is highly depending on the TDP settings and cooling solution of the laptop. Especially, longer loads will show varying results in different laptops.

Graphics

The integrated Intel UHD Graphics 620 (Intel Gen 9.5) is untouched from the 8th Gen Kaby Lake chips. With fast dual-channel memory it can reach the performance of a dedicated GeForce 920M.

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 (14nm+), the same as the 7th Gen Kaby Lake processors. 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.