After nine years of designing Chips at Apple, Gerard Williams III, has departed Apple last month ,

Lead designer of Apple's custom iOS chips from A7 to A12X,  Gerard Williams III, rumored to have departed the company. Gerard Williams III, senior director in platform architecture, departed Apple last month after nine years, according to CNET.
According to his Linked in page, Williams' presence goes back even further into Apple device history, as he served as the technical lead for the Cortex-A8 design, ARM's first super scalar core design and the heart of the iPhone 3GS. His role evidently grew over the years, with CPU architecture responsibilities eventually evolving into ownership of the entire system on chip (SoC), which houses CPU, graphics, image processing, secure enclave, motion, and AI cores.

A look at his patent portfolio shows he was a key force behind Apple's foray into mixed CPU core clusters starting with the A10 Fusion chip, and transitioning into full heterogeneous cores with the A11 Bionic. His body of work also includes an emphasis on cache, memory, and energy efficiency. These have become key differentiating features as seen in performance bench marking from sites such as AnandTech.
Via Macrumors