difference between 6th and 7th generation

You're probably not going to ditch that Skylake-powered machine you picked up last winter in favor of one with a 7th-Gen Core CPU. You'll see performance gains over last year's CPUs. So in order of performance, the 4.5-watt chips are named Core m3, Core i5 Y series and Core i7 Y series. To make matters more interesting, Intel is keeping the Core M brand for its entry-level Core m3 chip, which is the slowest and least expensive of the bunch. If you see a 'Y' at the end of the SKU, you have one of the chips formerly known as Core m5 or m7. However, because the 4.5-watt CPUs, also known as Kaby Lake Y series chips, are lower-power, they won't perform the same as a U series 15-watt CPU. The company hopes this change will help consumers, many of whom didn't understand the difference between a Core i5 and a Core m5. Intel has made a change to the way it names its low-power chips, eliminating the Core m5 and Core m7 designations and turning those two 4.5-watt chips into Core i5 and Core i7-branded SKUs. The result is a microarchitecture that's more power-efficient, so that the 7th-Gen Core chips can offer a performance boost over previous generations of Intel processors. Specifically, Intel said it improved the transistor channel strain on these CPUs.

Difference between 6th and 7th generation