There has been no shortage of rumors and speculation surrounding Apple's upcoming tablet PC (which for want of a better name will be referred to as the iSlate for the rest of this post), but the most recent talk from multiple sources inside Taiwan's component supply chain is that Apple plans to put a GPU from AMD inside the device. This rumor, however, couldn't get past our editors and so wasn't posted as news on the Digitimes front page, but it is still interesting to speculate how such rumors come into circulation.
As far as we know (and we did ask but received a "no comment" from a company spokesperson), AMD does not currently have any GPUs that support ARM processors. In fact it sold its related assets to Qualcomm in January 2009. Since developments inside AMD are usually leaked out to reporters well ahead of time, it seems highly unlikely that AMD could complete development on a whole new chip without any hints until now.
Second, even supposing AMD could complete initial design on a chip completely in secret, once it comes time to start planning how to manufacture it, AMD would need to let a foundry partner in on the project. Since AMD usually uses Taiwan-based foundries for its GPU manufacturing, the leaks would have started then. In order to get a chip out completely under the radar, AMD would have to be using a different foundry, most likely one of Globalfoundries' or its newly acquired Chartered ones, with a newly tailored process.
Put simply, that is a lot of secrecy and a lot of risk (combining a new chip design with a new manufacturing process only multiplies the number of issues) for Apple to go through, especially when there are already plenty of suitable GPU options for the iSlate available; Nvidia's Tegra or Qualcomm's Snapdragon for example. (If it turns out Apple does go with Snapdragon it would mean the rumors have a kernel of truth since Snapdragon most likely contains at least some IP originally developed by ATI.)
But the most logical supplier for the iSlate's graphics is Imagination Technologies. Apple has investment in Imagination and the company supplies graphics for the iPhone. Additionally, Imagination already has products available, such as its PowerVR SGX545, that are capable of meeting the expected needs of the iSlate in terms of 3D and multimedia performance.
With Apple already having several GPU options to power its iSlate, the idea that it has commissioned AMD to roll a whole new one seems like a joke. However, since there are no definites in the IT industry, we'll just have to wait until January 27 to find out.