Question: Jim Keller is a microprocessor engineer most well known for his work at AMD and Apple, he was involved in designing which 32-bit package on package (PoP) system-on-a-chip (SoC) designed by Apple Inc. and manufactured by Samsung? 
Sentence (from "Apple A4"): It combines an ARM Cortex-A8 CPU with a PowerVR GPU, and emphasizes power efficiency.
Relevant evidence: No