Deconstructing processors like the A4 usually happens behind the closed doors of only a handful of companies. These global reverse engineering firms are the investigative arm of the electronics marketplace, gumshoes who do research for the people who need to find out who is making what circuitry, as well as what manufacturing process they’re using to do it.
They’re the ones who delve deep into processors, audio controllers, and every other part you’d find inside a cell phone or iPad, figuring out layer by layer the exact composition of each package.
We partnered with the best company in the semiconductor reverse engineering trade, Chipworks, to bring you a closer look at how semiconductor teardowns are conducted, as well as a peek inside the iPad’s chips.
Chipworks has X-rayed, cross-sectioned, and ground through the A4 processor. In addition to showing you what’s inside, we’re also going to show you how they did it.
What did we find?
- The A4 package has three layers: two layers of RAM (Samsung K4X1G323PE), and one layer containing the actual microprocessor.
- This Package-on-Package construction gives Apple the flexibility to source the RAM from any manufacturer they want—they’re not locked into Samsung.
- It’s clear from both hardware and software that this is a single core processor, so it must be the ARM Cortex A8, and NOT the rumored multicore A9.
- We don’t expect to find any markings from PA Semi, Apple’s recent acquisition, but it’s safe to assume they played a major role in designing this package.
- Every iPhone processor that we have dissected has had a Samsung part number on the processor die. We have not found any such Samsung markings on the A4 (outside of the DRAM), perhaps the clearest sign to date that Apple is now in firm control of their semiconductor design.
- There’s nothing revolutionary here. In fact, the A4 is quite similar to the Samsung processor Apple uses in the iPhone. The primary focus of this design was minimizing power consumption and cost.
- Software benchmarks indicate that the A4 has the same PowerVR SGX 535 GPU as the iPhone 3GS, but verifying this via hardware is quite difficult. If this is true, and it likely is, graphic performance on the iPad is fairly poor relative to the screen size.