Several important features of the Intel Nehalem processor are better processor core management. The quad-core Nehalem chip utilizes symmetric multi-threading (SMT) technology, and each core can run two threads simultaneously. If SMT is enabled, the processor can grow up to 4 threads from 4 threads running before enabling.
SMT is generally configured in BiOS in, you can make changes at startup. Because the Nehalem processor shares some resources between threads, the role of SMT is to double the performance and throughput of the processor. Whether your application is running SMT or not running, these need to be tested by specific testing of your application.
this thread to discuss how to work, I will talk about four cores each running a thread - a state which disables SMT technology. Please note that this is the case where the vendor is configured in a typical Nehalem computer.
Nehalem architecture is very concerned about the core code for each active run. When the core is still inactive for a certain amount of time, the transistor driver will turn off the core of the processor. This feature is designed to save energy. The processor can also increase the active core frequency to improve performance. This option is called Turbo mode, and Turbo mode needs to be specifically enabled in some systems.
So all this magical thing happened, because this function, you need to be with the operating system. The key is to ensure that the active core of the processor has enough time to turn off its transistors. This was difficult to achieve before Windows 7 was released. Although the thread that creates the application is scheduled and executed by its operating system. Applications can't control themselves, they can only control which pipes are used. Prior to Windows 7, the Windows kernel would not consider scheduling a thread to run the available core before the thread was executed. (If the core is not available, Windows thread scheduler will select a running thread is closed or shut down the thread is waiting for the exchange. Decide which threads to be used is the key issue.)
developers can Use some kind of control technique to select the level relationship of the processor throughout the execution core call. This feature allows developers to specify the core that runs on a thread. Most operating systems, including Windows, are treated as a single command, not a request from a processor application, which limits their ability to accept requests (although in practice, they mostly complete requests). However, this programming method is generally not encouraged because it tends to reduce the efficiency of scheduling work. In most cases, scheduling decisions about which runtime and location to take are no easier than when programmers write code algorithms.
due to previous Windows for its scheduling threads is no predetermined plan, and therefore an application that uses three threads, you may see these threads will take turns using the four core Nehalem. As a result, the power saving feature and the Turbo mode will be affected because no core will remain inactive for a long time. However, in Windows 7, it is often arranged that threads run on the same kernel instead of letting them work in turn. Three-threaded applications usually use only three cores, so the fourth core of the Nehalem processor can be turned off. This significantly reduces the
supply of power, but also to improve the performance in two ways: Turbo mode, as described above, and a secondary cache mode, i.e. better cache application. The real victory is in energy saving. In desktop systems, power consumption may not be the most important standard, but they are very important for servers and mobile devices. Especially for mobile users, when enjoying longer battery life, Nehalem's mobile processors will appear in consumer electronics.