The main frequency, also called the clock frequency, in megahertz (MHz) or gigahertz (GHz), is used to indicate the speed of the CPU's arithmetic and data processing. Usually, the higher the main frequency, the faster the CPU can process data.
The main frequency of CPU = external frequency × multiplication factor. There is a certain relationship between the main frequency and the actual computing speed, but it is not a simple linear relationship. Therefore, the main frequency of the CPU is not directly related to the actual computing power of the CPU, the main frequency indicates the speed of the digital pulse signal oscillation within the CPU. Examples of this can be seen in Intel's processor products: a 1 GHz Itanium chip is able to perform almost as fast as a 2.66 GHz Xeon/Opteron, or a 1.5 GHz Itanium 2 is about as fast as a 4 GHz Xeon/Opteron. the CPU's computing speed also depends on the CPU's pipeline, bus, and other aspects of the CPU's performance metrics.
2 - External Frequency
The external frequency is the base frequency of the CPU in MHz, and the external frequency of the CPU determines the speed of the entire motherboard. To put it plainly, in desktop PCs, the overclocking referred to is the overclocking of the CPU's external frequency (of course, in general, the multiplier frequency of the CPU is locked), and I believe this point is well understood. But for the server CPU, overclocking is absolutely not allowed. As mentioned earlier, the CPU determines the operating speed of the motherboard, and the two are synchronized. If the server CPU is overclocked and the external frequency is changed, it will produce asynchronous operation (many motherboards on desktop computers support asynchronous operation), which will result in the instability of the entire server system.
The vast majority of computer systems in the external frequency and the motherboard front-side bus is not synchronized speed, and the external frequency and front-side bus (FSB) frequency and easily be confused.
3-Bus Frequency
AMD SEED II X4 955 Black Box
The Front Side Bus (FSB) is the bus that connects the CPU to the Northbridge chip. The Front Side Bus (FSB) frequency (i.e., bus frequency) is a direct influence on the speed of direct data exchange between the CPU and memory. There is a formula to calculate, i.e., data bandwidth = (bus frequency x data bit width)/8. The maximum bandwidth of data transmission depends on the width and transmission frequency of all simultaneously transmitted data. Let's say the Xeon Nocona, which supports 64-bit, has a front-end bus of 800MHz, according to the formula, its maximum bandwidth for data transfer is 6.4GB/sec.
The difference between the external frequency and the frequency of the front-side bus (FSB): the speed of the front-side bus refers to the speed of data transmission, and the external frequency is the speed of synchronous operation between the CPU and the motherboard. That is to say, 100MHz external frequency specifically refers to the digital pulse signal oscillating 100 million times per second; while 100MHz front-side bus refers to the amount of data transfer acceptable to the CPU per second is 100MHz × 64bit ÷ 8bit/Byte = 800MB/s.
4-Multiplier coefficients
The multiplier coefficients refer to the CPU's relative proportionality between mains frequency and external frequency. The multiplier factor is the relative ratio between the CPU's main frequency and external frequency. For the same external frequency, the higher the multiplier, the higher the CPU frequency. However, in reality, a higher multiplier is not significant in the context of the same external frequency. This is because the data transfer speed between the CPU and the system is limited, the pursuit of high main frequency and get a high multiplier CPU will appear obvious "bottleneck" effect - the CPU from the system to get the data limit speed can not meet the speed of the CPU computing. In general, in addition to the engineering sample version of Intel's CPU is locked multiplier, a small number of Intel Core 2 core Pentium Duo E6500K and some of the supreme version of the CPU does not lock the multiplier, and AMD did not lock the AMD black box version of the CPU (that is, do not lock the multiplier version, the user is free to adjust the multiplier, adjust the multiplier overclocking method than adjust the external frequency is much more stable).
5-Cache
The size of the cache is also one of the most important indicators of the CPU, and the structure and size of the cache has a very large impact on the CPU speed, the cache within the CPU runs at a very high frequency, generally operating at the same frequency as the processor, and the efficiency is much greater than the system memory and hard disk. In practice, the CPU often needs to repeatedly read the same block of data, and the increase in cache capacity can significantly improve the CPU internal read data hit rate, without having to go to memory or hard disk to find, in order to improve system performance. However, due to CPU chip size and cost considerations, caches are very small.
L1 Cache is the first level of CPU cache, which is divided into data cache and instruction cache. The capacity and structure of the built-in L1 cache have a greater impact on CPU performance, but the cache memory is composed of static RAM, the structure is more complex, in the case of the CPU core area can not be too large, the capacity of the L1 level cache can not be made too large. The general server CPU L1 cache capacity is usually 32-256KB.
L2 Cache (L2 Cache) is the CPU's second level of cache, divided into internal and external two chips. The internal chip L2 cache runs at the same speed as the main frequency, while the external L2 cache is only half of the main frequency.
The L2 cache capacity also affects the performance of the CPU, and the principle is that the bigger the better, the largest capacity of the CPU for home use in the past is 512KB, and the laptop can also reach 2M, while the L2 cache of the CPU for servers and workstations is even higher, and it can reach 8M or more.
L3 Cache (Level 3 Cache), divided into two kinds, the early one is external, memory latency, and at the same time improve the performance of the processor when large data volume calculations. Reduce memory latency and improve the ability to compute large amounts of data are very helpful to the game. And in the server field adding L3 cache is still a significant improvement in performance. For example, a configuration with a larger L3 cache utilizes 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.