Q. Explain about Hyper-threading?

Non threaded program instructions are executed in a single order at a time until the program completion. Presume a program have four tasks namely A, B, C, D. Assume that every task comprises 10 instructions involving a few I/O instructions. A simple sequential execution would need A→ B→ C→ D sequence.

In a threaded system these tasks of a single program/process can be performed in parallel offered is no data dependency. Because there is just one processor these tasks will be executed in threaded system like interleaved threads e.g. 2 instructions of A, 3 instructions of B, 1 instruction of C, 4 instruction of D, 2 instruction of C until completion of threads.

Hyper-threading allows 2 threads A & B to execute at the same instance. How? Some of the more significant parts of CPU are duplicated. So there exist 2 executing threads in CPU at the exact same instance. Please note that both these sections of the CPU works on same memory space (because threads are same program). Ultimately dual CPUs will enable computer to execute two threads in two different programs at the same instance.

So Hyper-threading technology enables a single microprocessor to behave as two separate threaded processors to operating system and application program which use it.