March 22, 2012 — Apple’s ARM-based processors have created a point of hardware differentiation in applications processors. With the A5X, Apple is going with a much larger die at the 45nm node (shared across the 2 prior generations), shares Chipworks. It’s also turned off the PoP track.
The Apple A4, still a commercially viable Apple processor, measures 53.3mm². Only two (and a half?) generations later, the Apple A5X form factor is 165mm² — 3.1x larger. All three of the processors — A4, A5, and A5X — are 45nm chips. By way of further comparison, another flagship applications processor, the NVIDIA Tegra 3 is 82mm², and fabricated in a similar 40nm generation by TSMC, so it is (more or less) consistent with the A5.
Apple changed its chip packaging with the A5X, moving from a package-on-package (PoP) design with the DRAM to DRAM going on the other side of the substrate. This type of packaging theoretically has disadvantages in bill of materials (BOM) simplification and performance, due to the increased chip-to-memory routing. Chipworks considers potential heat issues might be to blame for decoupling the chip and DRAM in the new layout. At the 32nm node, Apple should see lower power consumption and return to the PoP packaging.
Apple A4 Polysilicon Die = 7.3 x 7.3mm
Apple A5 Polysilicon Die = 10.09 x 12.15mm
Apple A5x Polysilicon Die = 12.90 x 12.79mm
Access the teardown report and download images of the Apple A5X and prior-generation die at http://www.chipworks.com/en/technical-competitive-analysis/resources/recent-teardowns/2012/03/the-apple-a5x-versus-the-a5-and-a4-%E2%80%93-big-is-beautiful/