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? 

Related documents: [0]  [DOC] The Apple A4 is a 32-bit package on package (PoP) system-on-a-chip (SoC) designed by Apple Inc. and manufactured by Samsung. It combines an ARM Cortex-A8 CPU with a PowerVR GPU, and emphasizes power efficiency. The chip commercially debuted with the release of Apple's iPad tablet; followed shortly by the iPhone 4 smartphone, the iPod Touch (4th generation), and the Apple TV (2nd generation). It was superseded by the Apple A5 processor used in the iPad 2 released the following year, which was then subsequently replaced by the Apple A5X processor in the iPad (3rd generation). [END] 
[1]  [DOC] Jim Keller is a microprocessor engineer most well known for his work at AMD and Apple. He was the lead architect of the AMD K8 microarchitecture (including the original Athlon 64) and was involved in designing the Athlon (K7) and Apple A4/A5 processors. He was also the coauthor of the specifications for the x86-64 instruction set and HyperTransport interconnect. From 2012 to 2015, he returned to AMD to work on the AMD K12 and Zen microarchitectures. [END]  
Answer: Apple A4
Apple A4