Apple GPUs are based on AMD's Polaris 11
 

AMD has two GPUs which should make future Mac notebooks and PCs and both are based on Polaris 10 and 11 GPUs. Our original story yesterday smoked out a few more details from our industry sources.

The first chip which will probably head to Mac All-in-Ones or notebooks is a less than 40W TDP part MXM based GPU that has 10 Compute Units each with 64 compute cores. The total number of compute units is 640 and the card has 4GB RAM. The memory works at 8 GBbps and the card has up to five Display Ports or other video connectors. With 14nm FinFET manufacturing, AMD / RTG can squeeze much more performance in the same power envelope compared to 28nm GCN cards. These R2x0 models are Apple's current flavour. Radeon R2x0 parts have been around since late 2013 and now is a good time to replace them with 14nm new GCN 4.0 architecture.

http://fudzilla.com/news/graphics/40...laris-11-based