The official press release JEDEC committee informed about the availability of updated standard specification High-Bandwidth Memory or HBM. Formally, the basic standard JESD235 updated to version JESD235A. This is what we mean by the earlier second generation memory or HBM HBM 2.0.
Meanwhile, there is significant changes in specifications . Until now, the HBM stack comprises four layers, each of which - a memory chip (not including a separate layer controller). The updated standard allows not only the arrangement of the four memory chips, but also from two or eight (two-high, four-high, high-8). Of course, all vertical connections - is through TSVs-holes). The total capacity of chips in the stack can range from 1 GB to 8 GB.
The width of the stack memory interface has not changed and is 1024 bits, but the exchange rate is raised . If each chip as part of HBM graphics AMD Radeon R9 Fury X communicates with GPU Fiji at speeds up to 128 GB / s, the updated standard allows the exchange rate to each stack (each chip) at up to 256 GB / s. The four chips on a substrate, as it is easy to calculate the exchange will provide speeds of up to 1 TB / s.
It is worth noting that the number of channels when accessing memory segments has not changed and is 8 (128 Gbit / s per channel). In the case of eight layers on each crystal will occur in one channel, whereas in the case of four layers for each memory layer may consist of two channels. This allows memory manufacturers to create easy-to-stack combination of them playing capacity and bandwidth.
The Committee also made a number of additions to the standard HBM. These changes include the emergence of new architecture (for the internal breakdown of the 1024-bit bus on separate channels), as well as improved self-test function. An important addition is the appearance of the "temperature alarm", which in the case of overheating of the stack provides all the power controller stack to return to a temperature in the working channel. The updated specifications are available for download from JEDEC.