Speculation around the design of the A6 processor at the core of the iPhone 5 has reached a fever pitch in the last few days. All that I have seen so far focuses on particular variants of the CPU and GPU. One might even say these cores are the whole discussion. It is widely believed that the A(x) processors are simply a CPU and GPU (now with multiple cores) tied together with a bit of transistor glue that makes everything work. If true, that's a shame.
Back in January 2010, before the iPad was introduced, I recounted a comment Steve Jobs made after Apple's 2008 acquisition of PA Semi acquisition in April 2008. Paraphrasing Jobs: "We want to further differentiate our products through IC design." I have always taken this to heart, making it the working premise of our analyses of the A4 and A5. We now extend this approach to the A5X and forthcoming A6.
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The A5X variant emerged in March with the introduction of the iPad3. It was a relative huge die. One can quickly compare the A5 and A5X die photos and see the majority of the increase in die size is related to the addition of two GPU cores. I say majority because there is more to it than that.
The A5 GPUs consumed approximately 30 mm2, or 24 percent of the total die area. This number increases to 62 mm2 , or 40 percent of the total die area for the A5X. In both cases, the dual ARM cores consume approximately 18 mm2.
Does this account for all the increase in die size? The short answer is no.