HBM base die
Beginner
The bottom chip in a memory stack. It doesn’t store data. It passes data between the memory chips above it and the processor.
Novice
The logic die at the bottom of an HBM stack. Through-silicon vias bring data down from the DRAM dies above, and the base die drives the wide interface to the processor through its microbumps.
Expert
Holds the PHYs that drive the stack’s interface. That interface sits within a few millimeters of the processor’s PHY because the unterminated interposer wires lose bandwidth quickly with length.
Explained in Packaging and chiplets (Systems).
See also: HBM (High Bandwidth Memory), Through-silicon via (TSV).