This is an interesting story, apparently AMD secured the luxury of getting exclusive access to Hynix HBM2 graphics memory. The second iteration of High bandwith memory (stacked memory to be used on-die on the GPU) would be limited in its availability, AMD this way can secure exclusive access to it.

The rumor comes from wccftech though, so that is a bit icky as any news is news for that website, whether it's wrong or right doesn't matter. Based on a claim from 'sources within AMD' AMD is trying to get their hands on pretty much all HBM2 memory to block Nvidia. Nvidia will be using HBM2 with Pascal GPUs that should be released in 2016.

It also isn't sure if Hynix indeed is the company involved, however since Hynix is the only party making 3D stacked HBM graphics memory, that kinda speaks for itself. The current limitation for HBM graphics memory basically is the clock frequency, the number of stacks and thus the 4 GB limitation. Foir HBM2 that will change ,more stacks means more memory and the bandwidth in gen 2 would be higher as well. looking at some documents, the memory bandwith will be doubled up and HBM2 will allow for a total of 8GB of graphics memory.