[EDIT]hmmm.....whats going on at AMD? (and history of 3Dfx Rampage)

[SteelCrysis]

http://wccftech.com/sk-hynix-hbm2-radeon-vega-2017/

There have been slight modifications to the catalog. Previously, SK Hynix had listed both 1.6 Gbps and 2.0 Gbps HBM2 for availability in Q4 2016 but that doesn’t seem to be the case anymore. Currently, only one product has been mentioned. The specific part number is “H5VR32ESM4H-H1K” and comes in the 5mKGSD package. This is a part holding a capacity of 4GB on a 4-Hi stack that operates at 1.2V. The package operates at 1.6 Gbps with a total bandwidth output of 204.8 GB/s.
...
Some calculations reveal that the Radeon Vega graphics card with HBM2 will feature a lower bandwidth than the competing enthusiast product. The card will be considered flagship by AMD and NVIDIA’s flagship right now is the Titan X (Pascal). This card features a memory bandwidth of 480 GB/s on a GDDR5X interface that carries a 12 GB VRAM buffer.

We know this as fact that Vega GPU comes with two HBM2 stacks that are 4-Hi configured and hold 4GB capacity. This would indicate that the card would feature up to 8 GB VRAM until higher density memory or more number of stacks are available on the HBM2 products. This also gives us a total bandwidth of 409.6 GB/s which is lower than AMD’s first generation HBM product, the Fury X, which operated with a bandwidth of 512 GB/s.