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Upgrading And Repairing PCs 21st Edition: Processor Features

Hyper-Threading Technology

Intel’s HT Technology allows a single processor or processor core to handle two independent sets of instructions at the same time. In essence, HT Technology converts a single physical processor core into two virtual processors.

HT Technology was introduced on Xeon workstation-class processors with a 533 MHz system bus in March 2002. It found its way into standard desktop PC processors starting with the Pentium 4 3.06 GHz processor in November 2002. HT Technology predates multicore processors, so processors that have multiple physical cores, such as the Core 2 and Core i Series, may or may not support this technology depending on the specific processor version. A quad-core processor that supports HT Technology (like the Core i Series) would appear as an 8-core processor to the OS; Intel’s Core i7-3970X has six cores and supports up to 12 threads. Internally, an HT-enabled processor has two sets of general-purpose registers, control registers, and other architecture components for each core, but both logical processors share the same cache, execution units, and buses. During operations, each logical processor handles a single thread.

A processor with HT Technology enabled can fill otherwise-idle time with a second process for each core, improving multitasking and performance of multithreading single applications.

Although the sharing of some processor components means that the overall speed of an HT-enabled system isn’t as high as a processor with as many physical cores would be, speed increases of 25% or more are possible when multiple applications or multithreaded applications are being run.

To take advantage of HT Technology, you need the following:

  • Processor supporting HT Technology—This includes many (but not all) Core i Series, Pen-tium 4, Xeon, and Atom processors. Check the specific model processor specifications to be sure.
  • Compatible chipset—Some older chipsets may not support HT Technology.
  • BIOS support to enable/disable HT Technology—Make sure you enable HT Technology in the BIOS Setup.
  • HT Technology-enabled OS—Windows XP and later support HT Technology. Linux distributions based on kernel 2.4.18 and higher also support HT Technology. To see if HT Technology is functioning properly, you can check the Device Manager in Windows to see how many processors are recognized. When HT is supported and enabled, the Windows Device Manager shows twice as many processors as there are physical processor cores.