One of the most interesting news of yesterday apart from the launch of the iPad itself is that Apple officially joined the ranks of fabless semiconductors designers, alongside AMD, VIA, Qualcomm and so many others.
Apple purchased PA Semi back in April 2008 for $278 million and the A4 is the first product of this acquisition.
Although PA Semi (Palto Alto Semiconductors) had its roots in PowerPC rather than ARM, the fact that both were part of the RISC family possibly made it easier for its engineer to work on ARM designs. The list of ARM licensees can be found here.
Apple is reportedly one of the ARM architecture licensee although the Cambridge-based company has never officially confirmed this. Apple has an extensive history of partnership with ARM, back from the days when it was Acorn. The resultant fruit of their collaboration was the chip used in Apple's first PDA, the Newton.
Apart from the fact that the chip is known as the A4 and runs at 1Ghz, we don't know much about it. From Apple's official video, we can guess the following markings : h8mbt00v0mtr-oem; VTJK00782; 1SB009A 0940. It is likely that the chip was manufactured back in the fourth quarter of 2009 accoring to iFixit.
Brightsideofnews posits that the chip is a Cortex A9 MPCore model (Fudzilla says ARM Cortex 8) with an integrated memory controller and a Mali 50-series graphics processing unit which supports Open GL ES. This would make the A4 fairly similar to the Nvidia Tegra 2.
This does make sense however, we're sure that somehow Apple managed to integrate some custom designs in there particularly as it has some stake in ARM's graphic rival, another UK based company, Imagination Technologies.
In December 2008, we wrote that "The purchase of PA Semi will reduce Apple's dependence on Samsung's ARM technology and will give it more control over the development of the chip architecture and reduce the risk of product delays."