One little tidbit we didn't know before about AMD's Radeon R9 Fury "Fiji" lineup is that you will not be able to overclock the memory. AMD claims the HBM technology is too new and argues that it already has more than enough bandwidth, therefore they won't enable this feature in AMD Overdrive.
One of the biggest features of Fiji is the inclusion of 4GB of HBM1 memory. We’ve already talked about high-bandwidth memory extensively in this article, so we’ll just leave it at that and you can go back and read that if you need more information. AMD is letting us say that the 4GB of HBM1 memory is running at 500MHz on a 3096-bit wide memory bus. At this clock speed it is capable of hitting 512GB/s of memory bandwidth. One interesting thing that we just learned this week is that AMD will not allow you to overclock the memory when the first Fiji cards are released. AMD feels that the memory technology is too new and there is more than enough bandwidth, so they are locking down the ability to overclock the memory in AMD Overdrive. This might change down the road, but for the time being only the core clock can be overclocked by end users.