Hyper Threading

  Intel’s Hyper-Threading Technology brings the concept of simultaneous multi-threading to the Intel Architecture. 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 processors will persist and execute simultaneously on shared execution resources.

The first implementation of Hyper-Threading Technology was done on the IntelXeonprocessor MP. In this implementation there are two logical processors on each physical processor. The logical processors have their own independent architecture state, but they share nearly all the physical execution and hardware resources of the processor. The goal was to implement the technology at minimum cost while ensuring forward progress on logical processors, even if the other is stalled, and to deliver full performance even when there is only one active logical processor.

The potential for Hyper-Threading Technology is tremendous; our current implementation has only just begun to tap into this potential. Hyper-Threading Technology is expected to be viable from mobile processors to servers; its introduction into market segments other than servers is only gated by the availability and prevalence of threaded applications and workloads in those markets.