Understanding of processor CPU parameters in assembling computer

Assembled computer friends generally must have a certain understanding of computer hardware, must understand its balance, the balance between components and hardware performance, processor is computer enthusiasts are very concerned about, so what kind of processor is a good processor (CPU)? Generally we look at the main processor parameters can be known in the current processor to what level, today to explain the processor CPU parameters.

1. 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 of a 1GHzItanium chip that behaves almost as fast as 2.66ghzxeon/opteron or 1.5ghzitanium2 about as fast as 4ghzxeon/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.

2. 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.

3. 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. Before we knew the IA-32 architecture had to have three major components: the memory controller hub (MCH), the I/O Controller hub and Pcihub, like Intel's typical chipset Intel7501, Intel7505 chipset, tailored for dual-strong processors, 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. The "HyperTransport" architecture not only solves the problem, but also improves the bus bandwidth more effectively, such as the Amdopteron processor, the flexible HYPERTRANSPORTI/O bus architecture allows 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 Amdopteron processor is not aware of the calcium 鹆 forgiveness?

4, the CPU bit and word length

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.

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.

L1 Cache (first-level cache) is CPU cache, which is divided into data cache and instruction cache. Built-in L1 cache capacity and structure of the CPU performance, but the cache is composed of static RAM, the structure is more complex, in the CPU core area can not be too large, the capacity of the L1-level cache can not do too much. The capacity of the L1 cache for a generic server CPU is usually 32-256kb.

L2 cache (Level two caching) is the second layer of CPU cache, divided into internal and external chips. The internal chip level two cache runs the same speed as the frequency, while the external level two cache is only half the frequency. L2 cache capacity also affects CPU performance, the principle is that the larger the better, now the largest household CPU capacity is 512KB, and servers and workstations with CPU L2 cache up to 256-1MB, some up to 2MB or 3MB.

L3 Cache (Level three buffer), divided into two, the early is external, now are built-in. In fact, the application of the L3 cache can further reduce the memory latency and improve the performance of the processor while calculating the large amount of data. Reducing memory latency and increasing the ability to compute large amounts of data can be very helpful to the game. Increasing the L3 cache in the server domain still has a significant performance improvement. For example, a configuration with a larger L3 cache uses physical memory more efficiently, so its slower disk I/O subsystem can handle more data requests. Processors with larger L3 caches provide more efficient file system caching behavior and shorter message and processor queue lengths.

The processor CPU Basic parameter is above these, through the processor hardware parameter comparison we can understand a certain processor how, the processor is good.