JEDEC this week published an updated version of its JESD235 specification, which that describes HBM and HBM2 DRAM. The new version of the standard allows memory manufacturers to increase capacities of future HBM stacks to 24 GB and boost their bandwidth to 307 GB/s per stack.
On the capacity front, the new version of the specification, JESD235B, had added support for 12-Hi chip stacks. With 4 more layers than the previous limit of 8-Hi stacks, this will allow memory manufacturers to produce 12 GB stacks at current densities, and 24 GB stacks in the future when 16 Gb layers become available. Though it's worth noting that while 12-Hi stacks are now part of the HBM specification, the group still lists the physical dimensions of a 12-Hi KGSD (known good stacked die) as "TBD", so it's not immediately clear right now whether 12-Hi stacks will follow the same 720μm typical/745μm maximum stack height rules as the current 2/4/8-Hi configurations. Otherwise the configuration of the stacks themselves are unchanged; the new KGSDs will continue to feature up to eight 128-bit channels as well as a 1024-bit physical interface.
https://www.anandtech.com/show/13732...-gbs-per-stack
JEDEC Updates HBM Spec to Boost Capacity & Performance
20th December 2018, 09:29
JEDEC Updates HBM Spec to Boost Capacity & Performance 
