JEDEC announced an update to the the JESD235 memory standard that deals with the second generation of high bandwidth memory (HBM). This update brings two key feature enhancements to the standard. First, it raises the capacity limit for each device to 24GB, and it also raises the speed threshold to 307GB/s.

If you are unfamiliar with HBM

Source: Hot Hardware – JEDEC Updates High Bandwidth Memory (HBM) Standard To 24GB Per Stack At Blistering 307GBps