GlobalFoundries only have 28nm HP process for GPUs, which AMD will use in 2015. So both Nvidia and AMD will use 28nm process throughout 2015 and won`t switch to newer nodes until 2016.
AMD = 28nm SHP Global Foundries
Nvidia = 28nm HPM TSMC
Well hopefully the SHP process allows AMD to increase clock speeds due to lower voltages and helps to increase the performance.. If they can get HBM memory in, it should make up for the shortfall from not using the 20nm process…