So what you're saying is that it makes no difference if you have 4Gb vs 8Gb on 4k resolutions? Or how does it not 'change performance'? Of course having only 4Gb addressable is a huge disadvantage. Once the tech matures and they go higher the old technology will be sitting in the dust.
No, I did not say any such thing. Allow me to highlight what I said.
The performance does not surprise me at all. They can throw 100GB of memory at it and it is not going to make any difference at less than 4K resolutions where most people are today and where the 980Ti ate the R9's lunch.
The HBM memory is doing about what I would expect, in the real world.
The cards performance was poorer at HD resolutions than the NVidia card. It remains to be seen what additional memory will do for UHD performance, as it will depend on the application being used. To suggest it would be better or worse is simply speculation, at this point.
However, AMD again screwed up their marketing by insisting this card is best at UHD. If they really believe that, then why bother with only 4GB of RAM when it needs more than that to realize its full potential at UHD resolutions? The contradiction is rather blatant.
They would have been better off waiting until they could populate the card with 6GB of RAM, or more, before claiming the performance is best at UHD resolutions.
At this point, it is not much more than an embarrassment for AMD.