Intel's multithreading architecture. Hyper-Threading makes one physical CPU appear as two logical CPUs. It uses additional registers to overlap two instruction streams in order to achieve an approximate 30% gain in performance. Multithreaded applications also take advantage of multicore CPUs. See multithreading
Standard Modes vs. Hyper-Threading
Applications must be multithreaded in order to take advantage of Hyper-Threading whether in single-core or dual-core machines.