As usual with product releases from Apple, numerous online sources compete to show detailed teardowns of the devices when they are available. Not only do people test the physical durability (even going so far as to blend the original iPhone), but they also benchmark the devices to see if they live up to the advertised specifications. With the iPad, however, some folks have gone one step further to bring a full teardown of the custom A4 chip.
The repair site iFixIt has teamed up with the semiconductor analysis company Chipworks to bring a very detailed view of the A4 chip, where they dissect it and look at it under high-powered optical and scanning electron microscopes as well as zap it with X-rays to take a peek inside.
Here are some of the details:
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 it wants; it's not locked into Samsung.
Samsung's 1Gb mobile DDR SDRAM (x2), with part number on each die being K4X1G323PE.
Decoding this part number shows there is 2Gb of memory inside. This translates into ~128MB of memory per die, for 256MB total.
There's not much revolutionary here. In fact, the A4 is quite similar to the Samsung processor Apple uses in the iPhone. 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.
In addition to looking at the details of the A4 chip, the teardown takes a peek at other components of the iPad, including the Broadcom and Texas Instruments controllers for the touch screen, as well as the audio, I/O, and power management units in the device.
If you like close-up pictures of circuit boards and semiconductors, check out the full teardown.
For the original iPad teardown from iFixIt, see this article.