You can see the GPU clusters in the blue boxes in the image below, the two CPU cores are in the green box. Notably, Imagination Technologies, the company who supplies the GPU IP, only lists variants of its Series 7XT graphics IP with 2, 4, 6, 8, and 16 "shading clusters". That means that Apple has likely used a semi-custom implementation.
The A9X chip is 147 square millimeters in size. That is 40% larger than the TSMC A9 chip in the iPhone 6s. The site notes that the L3 cache may not be present because the A9X features a memory interface twice as wide as the A9 which allows the chip to pass data to and from memory at twice the speed.
"I believe that this is enabled by the fact that a chip like the A9X, which powers a relatively large device such as the iPad Pro, has both more thermal headroom than the A9 (since the iPad Pro is a larger device that can handle a more power hungry chip) and can take up a larger area footprint than a phone chip (the memory inside of the iPhone 6s/6s is stacked on-top of the A9 package; the memory in the iPad Pro sits on the logic board)."
Check out the image and hit the link below for more detailed analysis on the A9X.
Read More [via Rick]