Definition: MCM

(MultiChip Module or MicroChip Module) A chip package containing several bare die known as "chiplets" that are mounted close together on a substrate (base). The short tracks between the chiplets eliminate much of the noise that external lines between separate chip packages can pick up. Multichip packaging also allows different chip technologies to be used in the same package; for example, CMOS and bipolar.

Chiplets Make One Large Chip
An MCM is an option for fabricating a system-on-chip (SoC), which has several specialized processing circuits. By combining several small chiplets on the same substrate, a comprehensive system can be manufactured at less cost because when everything is built on one large chip, the failure rate of the die on the wafer is higher. See SoC and die.

More Flexible for the Future
In addition, there is often no need to have all circuits on a chip at the same technology level. For example, the CPU and AI processor may be state-of-the-art, while memory and other components may not require upgrading as often. The critical components can be continuously enhanced without redesigninig the entire chip. See chiplet printer, MCM classes and MCP.