The new memory is per-pin compatible with GDDR5 and its biggest advantage is that it offers 10-12Gbps of bandwidth, versus the 7Gbps offered by today's GDDR5 memory. Longer-term, GDDR5X could eventually reach a bandwidth of up to 16Gbps.
In a presentation by a DRAM maker leaked to the web, GDDR5X is touted as offering double the data-rate per memory access, at 64 byte/access, compared to 32 byte/access by today's fastest GDDR5 standard, which is currently saturating its clock/voltage curve at 7 Gbps. GDDR5X breathes a new lease of live to the ageing DRAM standard, offering 10-12 Gbps initially, with a goal of 16 Gbps in the long term. GDDR5X chips will have identical pin layouts to their predecessors, and hence it should cost GPU makers barely any R&D to implement them.GDDR5X will be mass produced by firms like Micron and according to the rumor mill, both AMD and NVIDIA are considering adopting it. It seems the high-end GPUs will get HBM2 whereas mid-stream and performance cards will transition to GDDR5X to keep costs down.