What is external CPU frequency?

The external frequency is the baseline frequency of the CPU and even the entire computer system. The unit is MHz (Z ). In early computers, the synchronization speed between the memory and the motherboard is equal to the external frequency. In this way, it can be understood that the external frequency of the CPU is directly connected to the memory, synchronous running status between the two. For the current computer system, the two can be completely different, but the significance of the outer frequency still exists. In the computer system, most of the frequencies are based on the outer frequency and multiplied by a certain number of multiples, this multiple can be greater than 1 or smaller than 1.

When talking about the external frequency of the processor, we should mention two concepts closely related to it: Frequency Doubling and frequency clock, the clock speed is the clock frequency of the CPU; frequency doubling is the ratio of the frequency to the external frequency. The relationship between frequency, frequency, and frequency doubling: frequency = frequency X frequency doubling.

Before 486, the CPU clock speed is still in a low stage, and the CPU clock speed is generally equal to the external frequency. However, after the advent of 486, due to the continuous increase in the CPU operating frequency, some other devices (such as plug-in cards and hard disks) on the PC are restricted by the technology and cannot withstand a higher frequency, this limits the further improvement of the CPU frequency. Therefore, the frequency doubling technology is introduced. This technology can change the internal frequency of the CPU to a multiple of the external frequency, so as to increase the frequency by increasing the frequency doubling. The Frequency Doubling technology enables external devices to work on a lower external frequency, while the CPU frequency is a multiple of the external frequency.

In the Pentium era, the external frequency of the CPU is generally 60/66 MHz. Starting from Pentium II 350, the external frequency of the CPU has increased to 100 MHz. At present, the external frequency of the CPU has reached 200 MHz. Under normal circumstances, because the external frequency is the same as the memory bus frequency, when the CPU external frequency increases, the switching speed with the memory is also improved accordingly, which has a greater impact on the overall running speed of the computer.

The external frequency and the front-end bus (FSB) frequency are easily confused. The speed of the front-end bus refers to the speed of the bus between the CPU and the chip of the North Bridge. It also represents the speed of CPU and external data transmission. The concept of external frequency is based on the fluctuation speed of Digital pulse signals. That is to say, a 10 thousand MHz external frequency refers to a digital pulse signal that oscillates million times per second, it affects the frequency of PCI and other bus. The two concepts of Front-End bus and outer frequency are confusing, mainly because during a long period of time (mainly before the emergence of Pentium 4 and when the emergence of Pentium 4 ), the frequency of the front-end bus is the same as that of the outer frequency. Therefore, it is often called the front-end bus as the outer frequency, which leads to such misunderstanding. With the development of computer technology, it is found that the frequency of the front-end bus must be higher than that of the outer frequency. Therefore, QDR (quad date rate) technology or other similar technologies are used to achieve this purpose. The principles of these technologies are similar to the 2x or 4x of AGP. They make the front-end bus frequency twice, 4x, or even higher than the outer frequency, since then, the difference between the front-end bus and the external frequency has been paid attention.

The default external frequency of a CPU is only one, and the motherboard must support this external frequency. Therefore, you must pay attention to this when purchasing the motherboard and CPU. If the two do not match, the system will not work. In addition, many CPU frequencies have been locked, so extra-frequency is often required for overclocking. After the external frequency changes, many other frequencies of the system will change. In addition to the CPU clock speed, the frontend bus frequency, PCI, and other interface frequencies, including the hard disk interface frequencies, may change, causing the system to fail to run normally. Of course, some boards can provide the function of locking various interface frequencies, which is of great help to the success of overclocking. Overclocking is risky and may even damage computer hardware.