At the start of this article, we mentioned how 4GB of HBM may seem paltry compared to today's much larger GDDR5 capacities, but AMD does not see its memory capacity as a potential performance limitation. Larger GDDR5 memory capacities have been an inevitable byproduct of the need to increase memory bandwidth by increasing memory bus width, which in turn required more GDDR5 chips. AMD says that this has actually resulted in more capacity than is actually needed, and unused frame buffer capacities effectively serve no functional purpose whatsoever.
Now, because of the impressive 512GB/s of bandwidth made available by HBM, AMD no longer needs to increase memory capacity for the sake of more bandwidth. Instead, it all comes down to efficiency and how effective drivers are at managing the 4GB frame buffer.
Nevertheless, we expect larger HBM capacities in the future, either by utilizing larger DRAM dies per stack or increasing the number of stacks.