What is Hyper-Threading?

Hyper-Threading technology is a technique which enables a single CPU to act like multiple CPU's.

A CPU is made up of many smaller components. At any given time, one of these components might be busy, while the other components are waiting to be utilized.

Hyper-Threading enables different parts of the CPU to work on different tasks concurrently. In this way, a CPU with Hyper-Threading appears to be more than one CPU.

A CPU with Hyper-Threading has two sets of the circuits which keep track of the state of the CPU. This includes most of the registers and the instruction pointer. These circuits do not accomplish the actual work of the CPU, they are the temporary storage facilities where the CPU keeps track of what it is currently working on.

The vast majority of the CPU remains unchanged. The portions of the CPU which do computational work are not replicated, nor are the onboard L1 and L2 caches.

Hyper-Threading duplicates about 5% of the circuits of the CPU. Depending upon the software applications in use, Hyper-Threading can results in a performance increase up to six times that amount.

Hyper-Threading is Intel's trademark for what is more commonly referred to in the industry as Simultaneous Multi-Threading (SMT).

Software Support for Hyper-Threading

Hyper-Threading performance advantages will only be realized when using Operating Systems which support multiple CPU's.

In these operating systems, each CPU with Hyper-Threading will be seen as two CPU's.

Operating Systems which support Hyper-Threading include Microsoft Windows NT 4.0, Microsoft Windows 2000, Microsoft XP Professional, and most Unix variants.