JEDEC Solid State Technology Association, the organisation responsible for worldwide standards in microelectronics, has now formally published the finalised GDDR5X SGRAM standard for implementation in the next generation of high performance graphics solutions. GDDR5X is a extension to the widely-used GDDR5 memory, building on it to offer VRAM at higher bandwidth without incurring the level of cost associated with entirely new memory manufacturing techniques such as High Bandwidth Memory (HBM).
The GDDR5X spec moves from an 8N-prefetch structure to 16N, which is a similar extension made in the derivation of DDR2 standards from DDR, and DDR3 from DDR2. GDDR5X signalling is capable of transferring 64 Bytes of data per memory access rather than 32, doubling the theoretical memory data rate from ~6Gbps to between 10 and 12 Gbps. As memory speeds continue to increase JEDEC are projecting a maximum possible date rate of up to 16Gbps.
Critically GDDR5X mandates no major design or electrical changes and uses a similar signalling model, so the relative additional cost of implementation should be low.
GDDR5X is likely to feature on next-generation high performance graphics that don't fit into the cost bracket of an HBM2 solution, but still justifies the increased performance over GDDR5. 2017's equivalent of the GTX 970 and R9 385 would be ideal candidates, potentially filtering down into the mid-range and mainstream sectors depending on how the new generation shakes out.
Adoption of GDDR5X is seen as critical improving performance in system workloads where memory bandwidth sees a high level of importance - most specifically very high resolution textures and new development paradigms such as Virtual Reality.
More information, including the full standards document, can be found at https://www.jedec.org/