CPU little knowledge, CPU basics

　　Bit and word length of 1.CPU

Bit: in digital circuits and computer technology using binary, code only "0" and "1", which either "0" or "1" in the CPU is a "bit."

Word Length: The number of digits in the computer technology that the CPU can process at one time (at the same time) is called word length. So the CPU that can handle 8 bits of data is usually called a 8-bit CPU. Similarly, 32-bit CPUs can handle binary data with a word size of 32 bits per unit time. The difference between byte and word length: Since the commonly used English characters are represented by 8-bit binaries, 8 bits are usually called a byte. Length of Word is not fixed, for different CPU, word length is not the same. A 8-bit CPU can process only one byte at a time, while a 32-bit CPU can handle 4 bytes at a time, and the same-word 64-bit CPU handles 8 bytes at a time.

　　2.CPU Extended Instruction Set

CPU relies on instructions to calculate and control the system, each CPU in the design of a series of its hardware circuit with a set of instruction system. command is also an important indicator of CPU, instruction set is one of the most effective tools to improve the efficiency of microprocessors. From the current mainstream architecture, instruction set can be divided into complex instruction set and simplified instruction set, and from the specific application, such as Intel's MMX (Multi Media Extended), SSE, SSE2 (streaming-single instruction Multiple data-extensions 2), SEE3 and AMD 3dnow! are all CPU extensions, enhancing CPU multimedia, graphics and Internet processing capabilities. We usually refer to the CPU's extended instruction set as the "CPU instruction set". The SSE3 instruction set is also currently the smallest instruction set, before MMX contains 57 commands, SSE contains 50 commands, SSE2 contains 144 commands, SSE3 contains 13 commands. Currently SSE3 is also the most advanced instruction set, the Intel Prescott processor has supported the SSE3 instruction set, AMD will add support for the SSE3 instruction set in the future dual-core processors, and this instruction set will also be supported by the U.S.-wide processor.

　　3. Frequency

The clock frequency is also called the unit MHz, which is used to indicate the CPU's operation speed. CPU's frequency = FSB x Frequency multiplier factor. Many people think that the frequency of the CPU to determine the speed of operation, this is not only a one-sided, but also for the server, this understanding has been biased. So far, no formula has been established to realize the numerical relationship between the frequency and the actual operation speed. Even the two largest processor manufacturers, Intel and AMD, there is also a big controversy, we from Intel's product development trend, we can see that Intel is focused on enhancing its own frequency of development. Like other processor manufacturers, someone once compared the whole of the United States with a fast 1G, which runs the equivalent of a 2G Intel processor.

Therefore, the CPU's frequency and CPU actual operational capacity is not directly related to the frequency of the CPU in the digital pulse signal oscillation speed. In Intel's processor offerings, we can also see an example where the 1 GHz Itanium chip can perform almost as fast as the 2.66 GHz Xeon/opteron, or 1.5 GHz Itanium 2 is about as fast as 4 GHz Xeon/opteron. CPU's operating speed also depends on the CPU's pipeline of various aspects of performance indicators.

Of course, the frequency and the actual speed is related, can only say that the clock is only the performance of the CPU one aspect, and does not represent the overall performance of the CPU.

　　4. FSB

The FSB is the base frequency of the CPU, which is also MHz. The FSB of the CPU determines the speed at which the entire motherboard runs. Frankly speaking, in the desktop, we call overclocking, is the FSB (of course, in general, CPU frequency is locked) believe this is very good understanding. But for the server CPU, overclocking is absolutely not allowed. In front of the CPU determines the speed of the motherboard, the two are synchronous operation, if the server CPU overclocking, changed the FSB, will produce asynchronous operation, (desktop many motherboards support asynchronous operation) This will cause the entire server system instability.

At present, most of the computer system FSB is also memory and the speed of synchronization between the motherboard, in this way, can be understood as the CPU FSB directly with the memory connection, to achieve the synchronous operation between the two states. FSB and front-end bus (FSB) frequency is very easy to confuse, the following front side bus introduces us to talk about the difference between the two.

　　5. Frequency doubling coefficient

The frequency multiplier coefficient refers to the relative proportional relationship between CPU frequency and FSB. In the same FSB, the higher the frequency of the CPU is higher. But in fact, in the same FSB premise, the high frequency CPU itself is not significant. This is because the speed of data transfer between the CPU and the system is limited, blindly pursuit of high frequency and the CPU will have a significant "bottleneck" effect-cpu from the system can not meet the limit of the speed of CPU operations. In general, except for the engineering version of Intel's CPU is locked frequency multiplier, and AMD has no lock before.

　　6. Caching

Cache size is also one of the important indicators of the CPU, and the structure of the cache and the size of the CPU speed is very large, CPU cache operating frequency is very high, and the processor is generally the same frequency of operation, work efficiency far greater than the system memory and hard drive. In actual work, the CPU often needs to read the same block of data repeatedly, and the increase of cache capacity can greatly increase the hit rate of the CPU's internal reading data, instead of looking for the memory or hard disk, to improve the system performance. But because of CPU chip area and cost factor to consider, the cache is very small.

　　7. Manufacturing process

The micron of manufacturing process refers to the distance between circuit and circuit in IC. The tendency of manufacturing technology is to develop towards the higher density. The higher the density of IC circuit design, means that in the same size of the IC, you can have a higher density, more complex functions of the circuit design. Now the main 180nm, 130nm, 90nm. The Government has recently indicated that it has a 65nm manufacturing process.

　　8.CPU kernel and I/O operating voltage

Starting from 586CPU, the CPU's operating voltage is divided into kernel voltage and I/o voltage, usually the core voltage of the CPU is less than or equal to I/O voltage. Kernel voltage is based on the size of the CPU production process, the general production process is smaller, the core operating voltage is lower; I/o voltage is generally 1.6~5v. Low voltage can solve the problem of excessive power consumption and high fever.

　　9. Front-side bus (FSB) frequency

The front-end bus (FSB) frequency (i.e. bus frequency) is directly affecting CPU and memory direct data exchange speed. There is a formula that calculates that data bandwidth = (bus frequency x Data bandwidth)/8, the maximum bandwidth of data transfer depends on the width and frequency of all simultaneous transmissions. For example, now support 64-bit Xeon Nocona, the front-end bus is 800MHz, according to the formula, its maximum bandwidth of data transmission is 6.4gb/seconds.

FSB and front-end bus (FSB) frequency difference: the speed of the front-end bus refers to the speed of data transmission, FSB is the CPU and the speed between the motherboard synchronization. In other words, 100MHz FSB refers to the digital pulse signal in the oscillation 10 million times per second, while the 100MHz front-end bus means that the CPU can accept the amount of data transfers per second is 100mhzx64bit÷8byte/bit=800mb/s.

In fact, now "HyperTransport" the emergence of the framework, so that the actual sense of the front-end bus (FSB) frequency has changed. We knew before that the IA-32 architecture must have three major components: the memory controller hub (MCH), the I/O Controller hub, and the PCI hub, such as Intel's typical chipset Intel 7501, Intel7505 chipset, tailored for a dual to strong processor, The MCH includes a front-end bus with a frequency of 533MHz to the CPU, with DDR memory and a front-end bus bandwidth of up to 4.3gb/seconds. But as processor performance continues to improve, it poses a lot of problems for the system architecture. and the "HyperTransport" architecture not only solves the problem, but also improves the bus bandwidth more effectively, for example, the AMD Opteron processor, the flexible hypertransport I/O bus architecture enables it to integrate the memory controller, Enables the processor to exchange data directly and in memory without passing the system bus to the chipset. In this case, the front-end bus (FSB) frequency in the AMD Opteron processor does not know where to start.