Intel Compilers for Windows
Hyper-Threading Technology, Dual Processors and Multi-Core
Intel Software Development Tools are the fastest and easiest way to maximise the latest features of Intel's Hyper-Threading Technology, Dual Processors and Multi-Core processors.
The Dual Processor
A traditional dual processor system contains two separate physical computer processors in the same chassis. The two processors are usually located on the same circuit board (mother board) but occasionally will be located on separate circuit boards. In this case, each of the processors will reside in its own socket. A dual-processor (DP) system can also be considered a subset of the larger set of a symmetric multiprocessor (SMP) system. A multi-processor capable operating system can schedule two separate computer processes or two threads within a process to run simultaneously on these separate processors.
Hyper-Threading Technology
Hyper-Threading Technology (HT Technology) was developed by Intel Corporation to bring the simultaneous multi-threading approach to the Intel architecture. With HT Technology, two threads can execute on the same single processor core simultaneously in parallel rather than context switching between the threads. Scheduling two threads on the same physical processor core allows better use of the processors resources.
HT Technology is available on Intel Xeon processors and some Intel Pentium 4 processors. HT Technology adds circuitry and functionality into a traditional processor to enable one physical processor to appear as two separate processors. Each processor is then referred to as a logical processor. The added circuitry enables the processor to maintain two separate architectural states and separate Advanced Programmable Interrupt Controllers (APIC) which provides multi-processor interrupt management and incorporates both static and dynamic symmetric interrupt distribution across all processors. The shared resources include items such as cache, registers, and execution units to execute two separate programs or two threads simultaneously. Requirements to enable HT Technology are system equipped with a processor with HT Technology, an OS that supports HT Technology and BIOS support to enable/disable HT Technology.
Note that it is also possible to have a dual processor system that contains two HT Technology enabled processors which would provide the ability to run up to 4 programs or threads simultaneously. This capability is currently available on Intel Xeon processors and these systems are currently available from several OEM making and selling Intel Xeon processor-based DP systems.
Dual Core
This term refers to integrated circuit (IC) chips that contain two complete physical computer processors (cores) in the same IC package. Typically, this means that two identical processors are manufactured so they reside side-by-side on the same die. It is also possible to (vertically) stack two separate processor die and place them in the same IC package. Each of the physical processor cores has its own resources (architectural state, registers, execution units, etc.). The multiple cores on-die may or may not share several layers of the on-die cache.
A dual core processor design could provide for each physical processor to: 1) have its own on-die cache, or 2) it could provide for the on-die cache to be shared by the two processors, or 3) each processor could have a portion of on-die cache that is exclusive to a single processor and then have a portion of on-die cache that is shared between the two dual core processors. The two processors in a dual core package could have an on-die communication path between the processors so that putting snoops and requests out on the FSB is not necessary. Both processors must have a communication path to the computer system front-side bus.
Note that dual core processors could also contain HT Technology which would enable a single processor IC package, containing two physical processors, to appear as four logical processors capable of running four programs or threads simultaneously
Multi Core
The multi core system is an extension to the dual core system except that it would consist of more than 2 processors. The current trends in processor technology indicate that the number of processor cores in one IC chip will continue to increase. If we assume that the number of transistors per processor core remains relatively fixed, it is reasonable to assume that the number of processor cores could follow Moore’s Law, which states that the number of transistors per a certain area on the chip will double approximately every 18 months. Even if this trend does not follow Moore’s Law, the number of processor cores per chip appears destined to steadily increase - based on statements from several processor manufacturers.
The optimal number of processors is yet to be determined, but will probably change over time as software adapts to effectively use many processors, simultaneously. However, a software program that is only capable of running on one processor (or very few processors) will be unable to take full advantage of future processors that contain many processors cores. For example, an application running on a 4-processor system with each socket containing quad-core processors has 16 processor cores available to schedule 16 program threads simultaneously.