A multiprocessing system is disclosed. The system includes a multithreading microprocessor including a plurality of thread contexts (TCs), each having a program counter and a general purpose register set for executing a thread. The microprocessor also includes a shared privileged resource, shared by the plurality of TCs rather than being replicated for each of the plurality of TCs, and privileged to be managed only by operating system-privileged threads rather than by user-privileged threads. The system also includes a multiprocessor operating system (OS), configured to manage the shared privileged resource, and to schedule execution of both the operating system-privileged threads and the user-privileged threads on the plurality of TCs.