Hyper-threading technology logically divides the processing unit of CPU into two parts.
Multi-core means that a CPU has multiple processing units.
Hyper-threading technology is a processor technology, which uses special hardware instructions to simulate two logical cores in a multithreaded processor as two physical chips, so that a single processor can "enjoy" thread-level parallel computing. Multi-threading technology can effectively enhance the processor's multi-tasking and multi-threading processing ability on operating systems and software that support multi-threading.
Hyper-threading technology can make multiple threads of operating system or application software run on a hyper-threading processor at the same time, in which two logical processors share a set of processor execution units and complete operations such as addition, multiplication and loading in parallel. Doing so can improve the processing capacity of the processor by 30%, because simultaneous application can make full use of each computing unit of the chip.
In the process of processing multiple threads, each logical processor in a multithreaded processor can respond to interrupts independently. When the first logical processor tracks a software thread, the second logical processor also starts to track and process another software thread.
For multi-core microprocessors, taking dual-core processors as an example, it is simply to integrate two processor cores on a CPU substrate and connect them through parallel buses. However, in order to avoid the conflict of CPU processing resources, the logical processor responsible for processing the second thread only uses the temporarily idle processing unit when running the first thread. Therefore, although multithreading technology can execute multiple threads at the same time, it is not like two real CPUs, each of which has independent resources. When two threads need a resource at the same time, one of them should temporarily stop and give up the resource until these resources are free. So the performance of hyper-threading is not equal to the performance of two CPUs.
P4 Hyper-Threading has two operation modes, single-task mode and multi-task mode. When the program does not support multiprocessing, the system will stop the operation of one logical CPU and concentrate resources on a single logical CPU. The performance of a single-threaded program will not be reduced because one of the logical CPUs is idle, but the stopped logical CPU will still wait for work and occupy certain resources. Therefore, if the hyperthreaded CPU runs in the program mode of single task mode, it may not reach the performance of the CPU without hyperthreading function, but the performance gap will not be too big. In other words, when running single-threaded application software, hyper-threading technology will even reduce system performance, especially when multi-threaded operating system runs single-threaded software.
It should be noted that the CPU with hyper-threading technology needs the support of chipset and software to give full play to the advantages of this technology. At present, the chipsets supporting Hyper-Threading Technology are: Intel i845GE, PE and silicon iSR658 RDRAM, SiS645DX and SiS65 1, which can directly support Hyper-Threading; Intel i845E and i850E can be supported by upgrading the BIOS, and VIA P4X400 and P4X400A can be supported, but there is no official authorization. Operating systems such as Microsoft Windows XP, Microsoft Windows 2003 and versions after Linux kernel 2.4.x also support Hyper-Threading Technology.
Dual-core processor has two processor cores with the same function on one processor based on a single semiconductor, that is, two physical processor cores are integrated into one core. In fact, the dual-core architecture is not a new technology, but the dual-core processor has always been the patent of the server, and now it has begun to spread.