iFixit's iPad teardown turned up the expected huge battery and dinky circuit boards, but of course our prime interest has been in the custom Apple A4 processor that keeps the iPad whipping along. While we know it's ARM based, Apple have been unduly coy in spilling any other information about the 1GHz chipset; iFixit decided to send the die over to Chipworks, who specialise in taking a more forensic look at silicon.
They found that, despite the "revolutionary" billing, in actual fact the A4 looks to consist of pretty straightforward components selected for their cost and sandwiched together into a custom package. The A4 has three layers - two of RAM, currently sourced from Samsung, and the microprocessor layer - with a single-core ARM Cortex A8 bearing neither Samsung nor PA Semi markings.
That means early speculation that Apple might use a dual-core ARM Cortex A9 was unfounded, and it also allows Apple to switch RAM providers without too much trouble should a better deal come along in the future. Chipworks reckon the GPU is the same PowerVR SGX 535 from the iPhone 3GS, though that's not definite yet. Overall, though, they believe Apple selected the components based on cost rather than innovation.