This paper presents a technique to implement operating system software more efficiently: as part of the processor architecture. Such an'architectural'implementation has two significant advantages over a conventional'software'implementation. First, it allows performance critical modules of the operating system to be implemented through specialized hardware or firmware. Second, it allows the implementation of the operating system to evolve with technology without any change to the basic design structure. The basis for the proposed technique is the application of a software structuring methodology called'type extension'. A model for the architectural implementation of a subsystem, which is structured through this methodology, is presented. It is shown that this model encompasses all conventional forms of implementation—hardware, firmware, software. The model establishes that architectural implementation allows a range of implementation choices; a software implementation utilizes only a small subset of these choices.