An interesting article over at The Linley Group discusses Apple’s work in churning out the A6 and how they got there. It’s a great read and well worth checking out.
Although Apple has been licensing cores from ARM for its previous processors, the company’s interest in CPU design dates back to its $278 million acquisition of PA Semi in April 2008. That acquisition included a CPU design team that had developed a high-performance PowerPC processor under the leadership of Jim Keller and Pete Bannon. More important, some of the team members had previously worked on low-power StrongArm processors under PA Semi CEO Dan Dobberpuhl at Digital Equipment (DEC) in the 1990s. Within a month of that deal, Apple secretly signed an architecture license with ARM that allowed the company to develop its own ARM-compatible CPUs, becoming one of the few companies in the world with that right.
While one group of PA Semi employees set to work on the Apple A4 processor using an ARM CPU core, another group began defining the microarchitecture for the new CPU. According to one source at Apple, Steve Jobs initially set an “insanely great” bar for the performance of the new CPU, but he eventually realized that his CPU team was limited by the same laws of physics that apply to everyone else. For whatever reason, the project took a long time to get through the initial definition and design phase.