Processor Types and Specifications - Upgrading and Repairing PCs - page 62

To take advantage of HT Technology, you need the following:
• Processor supporting HT Technology —This includes many (but not all) Core i Series,
Pentium 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.
Multicore Technology
HT Technology simulates two processors in a single physical core. If multiple simulated processors
are good, having two or more real processors is a lot better. A multicore processor, as the name
implies, actually contains two or more processor cores in a single processor package. From outward
appearances, it still looks like a single processor (and is considered as such for Windows licensing
purposes), but inside there can be two, three, four, or even more processor cores. A multicore
processor provides virtually all the advantages of having multiple separate physical processors, all at
a much lower cost.
Both AMD and Intel introduced the first dual-core x86-compatible desktop processors in May 2005.
AMD's initial entry was the Athlon 64 X2, whereas Intel's first dual-core processors were the
Pentium Extreme Edition 840 and the Pentium D. The Extreme Edition 840 was notable for also
supporting HT Technology, allowing it to appear as a quad-core processor to the OS. These
processors combined 64-bit instruction capability with dual internal cores—essentially two
processors in a single package. These chips were the start of the multicore revolution, which has
continued by adding more cores along with additional extensions to the instruction set. Intel
introduced the first quad-core processors in November 2006, called the Core 2 Extreme QX and
Core 2 Quad. AMD subsequently introduced its first quad-core desktop PC processor in November
2007, called the Phenom.
Note
There has been some confusion about Windows and multicore or hyperthreaded processors.
Windows XP and later Home editions support only one physical CPU, whereas Windows
Professional, Business, Enterprise, and Ultimate editions support two physical CPUs. Even
though the Home editions support only a single physical CPU, if that chip is a multicore
processor with HT Technology, all the physical and virtual cores are supported. For example,
if you have a system with a quad-core processor supporting HT Technology, Windows Home
editions will see it as eight processors, and all of them will be supported. If you had a
motherboard with two of these CPUs installed, Windows Home editions would see the eight
physical/virtual cores in the first CPU, whereas Professional, Business, Enterprise, and
Ultimate editions would see all 16 cores in both CPUs.