This work presents an Advanced Interface Bus (AIB)-compatible microcontroller unit (MCU) chiplet in 16nm FinFET CMOS. The MCU chiplet consists of three AIB channels, each providing 20 Tx and Rx pairs to support 80Gb/s/channel over 55μm - pitch microbumps. Two multi-chip modules (MCM) were constructed, one made of two MCU chiplets integrated on a 180nm passive silicon interposer, and the other made by pairing an MCU chiplet with a Stratix 10 FPGA over an Embedded Multi-die Interconnect Bridge (EMIB). The AIB interface provides 256Gb/s/mm-shoreline, consuming 0.83pJ/b at 0.9V and 1GHz. The two MCMs demonstrate the ease and versatility of modular 2.5D integration.