1. A multiprocessing system, comprising: a multithreading microprocessor, comprising: a plurality of thread contexts (TCs), each having a program counter and a general purpose register set for executing a thread; and a translation lookaside buffer (TLB), shared by said plurality of TCs rather than being replicated for each of said plurality of TCs, and privileged to be managed only by operating system-privileged threads rather than by user-privileged threads; and a multiprocessor operating system (OS), configured to manage said TLB, and to schedule execution of both said operating system-privileged threads and said user-privileged threads on said plurality of TCs.