Multi-chip module hybrid integrated circuit with multiple power zones that provide cold spare support

A multi-chip module hybrid integrated circuit (MCM-HIC) provides cold spare support to an apparatus comprising a plurality of ICs and/or other circuits that are not cold spare compliant. At least one core IC and at least one cold spare chiplet are installed on an interconnecting substrate having a plurality of power zones to which power can be applied and withdrawn as needed. When powered, the cold spare chiplets serve as mediators and interfaces between the non cold spare compliant circuits. When the cold spare chiplets are at least partly unpowered, they protect all interconnected circuits, and ensure that interconnected circuits that remain powered are not hindered by unpowered interconnected circuits. Cold spare chiplets can extend across boundaries between power zones. External circuits can be exclusively interfaced to a subset of the power zones. Separate power circuits within a power zone can be sequenced during application and withdrawal of power.