Apple A4 Dissected

Ifixit and Chipworks look into all the chips (by Xraying them) on the iPad board, including the Apple A4 processor. Then they dismantled it. Complete process is detailed at ifixit.

Step 6

• So what is a package? You're looking at one.

• This is a cross-section of the iPhone's ARM processor + RAM package. Click here to see it in its full, 2854x313 glory.

• The processor itself is the center rectangle. The silver circles underneath it are solder balls.

• The two rectangles above the processor are RAM dies. They are offset from each other to make room for the wirebonds, which you can't see in this shot.

• Having the RAM so close to the processor both reduces latency—making RAM access faster—and cuts power consumption, helping your battery last longer.

Step 16

• Before dismantling it, Chipworks took an X-ray image of the A4 processor to get a feel for how things are laid out inside.

• If you look closely, you can see hundreds of thread-like interconnects (wirebonds) that carry electronic signals between dies.

• The A4 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.

Step 18

• This is a die metal 8 layer.

• Every iPhone processor that we have dissected has had a Samsung part number on the processor die. We have not found any Samsung markings on the A4 (outside of the DRAM), perhaps the clearest sign to date that Apple is in firm control of the semiconductor design.

• 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.