HBM

High-bandwidth memory (HBM) is made by stacking memory chips vertically and placing them right beside a GPU or other AI chip. That arrangement lets data move to the processor much faster than conventional memory, which matters because large models must constantly move huge amounts of data.

HBM is produced by only a few manufacturers and is harder to make than ordinary memory, so its supply can limit how many AI chips get built. Memory makers' results and investment plans are often reported as signals of AI demand.

When a story says chip output is constrained, the limit may be HBM or advanced packaging rather than the processor itself.