The FSB is the reference frequency of the CPU and even the entire computer system. The unit is MHz (megahertz). In early computers, the synchronous running speed between the memory and the motherboard was equal to the FSB. In this way, it can be understood that the CPU FSB is directly connected with the memory to achieve synchronous operation between the two. For the current computer system, the two may not be the same, but the significance of the FSB still exists, most of the frequency of the computer system is based on the FSB, multiplied by a certain multiple to achieve, this multiple can be Greater than 1, it can also be less than 1.
Speaking of the processor FSB, it is necessary to mention two concepts closely related to it: frequency multiplication and main frequency, the main frequency is the clock frequency of the CPU, and the frequency multiplication is the multiple of the ratio of the main frequency to the FSB. Main frequency, FSB, frequency multiplication, and its relation: main frequency = FSB × frequency multiplier.
Before 486, the main frequency of the CPU is still in a lower stage, and the CPU's main frequency is generally equal to the FSB. After 486 appeared, due to the continuous increase of CPU operating frequency, while some other PC devices (such as cards, hard drives, etc.) are subject to process limitations and can not afford higher frequencies, thus limiting the further increase in CPU frequency. Therefore, there is a frequency multiplication technique, which can make the internal working frequency of the CPU to be a multiple of the external frequency, so that the main frequency can be increased by increasing the frequency multiplication. The frequency multiplication technique is to make the external device work at a lower FSB, and the CPU frequency is a multiple of the FSB.
In the Pentium era, the CPU's FSB was generally 60/66 MHz. Starting with the Pentium II 350, the CPU FSB increased to 100 MHz. The current CPU FSB has reached 200 MHz. Since the FSB and memory bus frequency are the same under normal conditions, After the increase of the CPU FSB, the exchange speed between the memory and the memory has also been correspondingly improved, which has a greater impact on improving the overall operating speed of the computer.
The FSB and FSB frequencies can easily be confused. The speed of the front-side bus refers to the speed of the bus between the CPU and the Northbridge chip, and more substantively expresses the speed of data transfer between the CPU and the outside world. The concept of FSB is based on the pulsation speed of digital pulse signals. That is, the 100 MHz FSB specifically refers to the digital pulse signal oscillating at 1 million times per second. It has more impact on PCI and other buses. Frequency of. The reason why the two concepts of FSB and FSB are confusing, the main reason is that in the previous long time (mainly before the appearance of the Pentium 4 and when the Pentium 4 appeared), the FSB frequency is the same as the FSB. Therefore, the front-side bus is often referred to directly as the FSB, eventually causing such misunderstandings. With the development of computer technology, people have found that the front-side bus frequency needs to be higher than the FSB, so QDR (Quad Date Rate) technology or other similar technologies are used to achieve this goal. The principle of these technologies is similar to AGP's 2X or 4X, which makes the frequency of the front side bus become 2 times, 4 times or even higher than the FSB. Since then, the difference between the front side bus and the FSB has only begun to gain attention.