TechInsights reveals the innards of SK Hynix's high bandwidth memory, in AMD's Radeon 390X Fury X graphics card.
SK Hynix, the Korean memory chip manufacturer, announced its high bandwidth memory (HBM) product in early 2014, claiming it to be the world’s first 8Gb module made using 2Gb, 20nm node, DDR4 SDRAM. It took nearly a year for the HBM modules to show up in a downstream product: in this case, AMD’s Radeon 390X Fury X graphics card.
We at TechInsights have a few of the Fury X cards in our lab and its GPU unit is shown below in Figure 1. The GPU die is seen in the center of the module with four Hynix HBM memory modules arranged around its perimeter. Both the GPU and the HBM modules are flip-chip bumped to a UMC fabbed interposer. This interposer is, in turn, bumped to a laminate substrate. The GPU is massive measuring in at 23mm by 27mm large, and is believed to be fabricated using TSMC’s 28nm HKMG process.
The HBM uses through silicon vias (TSVs) to connect the DRAM dies and base logic die together, and this is a fairly new technology for DRAM. Samsung has a 20nm DDR4 with four stacked DRAM dies with TSVs, but this part is not a wide I/O device, nor does it contain a base logic die. Hynix’s HBM has a 1,024-wide bus qualifying it as wide I/O. It employs a base logic die as an interface between the four DRAM die stack and an interposer that supports both the HBM modules and the AMD GPU. The HBM can be considered 3D packaging, while the laterally spaced apart layout for the GPU and HBM modules on the interposer makes for a 2.5D package.