Here are two side X-rays of the A4 processor.
The dark dots along the inside of the processor are solder balls connecting the dies together. These are known as Ball Grid Arrays (or BGAs) in the industry.
These pictures are shot at two focal points across the width of the processor. They were quick shots, so we apologize if they're a little fuzzy.
The DRAM in the A4 is made by Samsung, so wirebonds are coming from both sides—unlike other DRAM modules Chipworks has seen from other manufacturers.
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.
This is the SDRAM inside the A4. Yes, that's a Samsung logo. No, that doesn't mean Samsung designed the A4—just the RAM.
Samsung's 1 Gb mobile DDR SDRAM (x2)
The part number on each die is K4X1G323PE.
Decoding this part number shows there is 2Gb of memory inside. This translates into ~128MB of memory per die, for 256 MB total.
So now that we've seen the inside, what can we conclude?
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.
It's quite challenging to identify block-level logic inside a processor, so to identify the GPU we're falling back to software: early benchmarks are showing similar 3D performance to the iPhone, so we're guessing that the iPad uses the same PowerVR SGX 535 GPU.
The iPad has 256 MB RAM, same as the iPhone.
The A4 sips power. In fact, power consumption is probably the reason Apple hasn't stepped up performance much from the iPhone. In order to get 10 hours of battery life, the entire iPad (including display) has to pull less than 2.5 Watts on average.
That's it for the A4. Let's take a look at some of the other chips inside the iPad.