Competition is good, and perhaps one of the most obvious examples of this is the fact that AMD now has 8GB models inbound. Ofcourse, there was no technological restriction on it being 4GB in the first place as we pointed out before, and with the TITAN-X launch with 12GB the pressure is on for AMD to release an 8GB card.
AMD's Fiji Flagship Launches with 8GB 2.5D Interposer HBM Chip
We are growing ever closer to the launch of AMD's next high end flagship and Fudzilla.com have stated, citing internal sources, that the card will actually launch with 8GB of frame buffer. Considering the fact that we are talking about high bandwidth memory, that is an absolutely insane amount. 8GB HBM is in its early development stages and is very obviously the cutting edge of video graphics memory. The First Generation 4-Hi stack could only go upto 4GB but Second Generation 4-Hi stacks are capable of 8GB worth of capacity under high density PKG.
It is worth pointing out that it was the same pub which initially stated that the flagship would be limited to 4GB due to a technical limitation - something we pointed out as inaccurate in our article. The GPU will be using an interposer to stack the die in a 2.5D fashion so size of upto 2000mm^2 (for the interposer) are possible with 8GB being a laughably easy amount to achieve. Ofcourse it goes without saying that if AMD choses to go with high density PKG, the yield of said component would be lower than the lower density variants which net 4GB in the same footprint.
The bandwidth of the card will most probably be either 512 GB/s - 1024 GB/s depending on the combination used. 2.5D is the best option for high performance ASICs currently primarily because 3D stacking would result in a very very bad heat management. Since the memory would be stacked on top of the die, it would become very difficult to control the heat produced from the power hungry chips that are modern GPUs. Needless to say, this generation of GPUs just got very exciting and AMD's HBM memory appears to be on the cutting edge of Industry technology.