The folks at iFixIt hired the computer forensics muscle of Chipworks to X-ray, cross-section, grind through, and thoroughly photograph the Apple A4 processor used in the iPad. Here’s some of what they found:

* 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.
* Software benchmarks indicate that the A4 has the same PowerVR SGX 535 GPU as the iPhone 3GS, but verifying this via hardware analysis is quite difficult. If this is true, and it likely is, graphics performance on the iPad is fairly poor relative to the screen size.
* 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.

IFixIt also identified several other manufacturers, including Linear Technologies, Intersil, ST Micro, NXP, Cirrus Logic, Texas Instruments, and Broadcom. More information on these parts can be found toward the end of the teardown.

Chipworks’ lab is still running full-tilt, analyzing the iPad, and they’ll be updating their site as they discover more.

Photos courtesy of iFixIt and Chipworks.

A4 Teardown