NVIDIA uses all possible tricks with their Max-Q technology. Its main aim is to reduce heat output, making it possible for smaller laptops to integrate more powerful graphics cards.

Specs overview

Spec-wise both graphics cards are a bit different from each other – the newer one uses the 12nm manufacturing process of the Turing architecture, whilst the older Pascal GPU is built around a 16nm one. This helps the GTX 1660 Ti Max-Q to use 60W of power, compared to the 80-90W of the GTX 1070 Max-Q. Additionally, the GTX 1660 Ti Max-Q uses 1536 CUDA cores, compared to 2048 for the older GPU.
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https://laptopmedia.com/comparisons/nvidia-geforce-gtx-1660-ti-max-q-vs-gtx-1070-max-q-battle-of-the-max-qs/