Intel Hyper Threading

    Отсюда (Hyper-Threading Technology.pdf):
    "Hyper-Threading Technology makes a single physical processor appear as two logical processors; the physical execution resources are shared and the architecture state is duplicated for the two logical processors. From a software or architecture perspective, this means operating systems and user programs can schedule processes or threads to logical processors as they would on multiple physical processors. From a microarchitecture perspective, this means that instructions from both logical rocessors will persist and execute simultaneously on shared execution resources."
    "Hyper-Threading Technology makes a single physical processor appear as multiple logical processors [11, 12]. To do this, there is one copy of the architecture state for each logical processor, and the logical processors share a single set of physical execution resources. From a software or architecture perspective, this means operating systems and user programs can schedule processes or threads to logical processors as they would on conventional physical processors in a multiprocessor system. From a microarchitecture perspective, this means that instructions from logical processors will persist and execute simultaneously on
shared execution resources."
    "Each logical processor maintains a complete set of the architecture state. The architecture state consists of registers including the general-purpose registers, the control registers, the advanced programmable interrupt controller (APIC) registers, and some machine state registers. From a software perspective, once the
architecture state is duplicated, the processor appears to be two processors. The number of transistors to store the architecture state is an extremely small fraction of the total. Logical processors share nearly all other resources on the physical processor, such as caches, execution units, branch predictors, control ogic, and buses."
    В статье стоит прочитать хотя бы начало, для составления представления об общей архитектуре процессоров и набраться buzzwords:) вроде chip multiprocessing (CMP), time-slice multithreading, cache miss, branch mispredictions, simultaneous multi-threading, logical/physical processor, out-of-order execution.