1. CPU Frequency = External Frequency
2. CPU Frequency = Main Frequency
3. Front End Bus Frequency
4. System Bus Frequency
5. Multiplier Frequency
5. System bus frequency
5. Multiplier frequency
Relationship to each other:
The external frequency of the CPU is the base frequency of the CPU and even of the entire computer system in MHz (megahertz). Most of the frequencies in a computer system are based on the external frequency, multiplied by a certain number of times. the AGP bus frequency is usually a fixed 66MHz. secondly, the front side bus is usually 2 to 4 times the external frequency of the CPU, and there is no fixed number of times, and the cpu model and the motherboard chipset. Then the system bus, this should be a more general concept, can refer to all the buses in the system (front side bus, agp bus, pci bus, etc.), but also sometimes refers to the bus between the north and south bridges, and there is no fixed frequency and algorithm.
CPU frequency = external frequency x multiplier (or main frequency = external frequency x multiplier)
IntelCPU front side bus = external frequency * 4 (MHz)
AMDCPU front side bus = external frequency * 2 (MHz)
CPU data bandwidth = front side bus * 8 (MB/s)
Memory bandwidth = Memory equivalent Operating frequency * 8 (MB / s)
(Note that the unit is byte, here the unit of 8 is byte B, not refers to the 8 bit, is 64bit / 8 = 8B to get, 64bit is the number of bits of data transmitted by the computer each time)
Bus is a set of transmission lines to one or more source components to one or more destination components to transfer information. In layman's terms, it is a common **** connection between multiple components for transferring information between them. The bus frequency is often described in terms of speed expressed in MHz. There are many types of buses, and the front-side bus, known in English as FrontSideBus and often denoted by FSB, is the bus that connects the CPU to the Northbridge chip.
The CPU is connected to the Northbridge chip through the FrontSideBus (FSB), which in turn exchanges data with the memory and graphics card through the Northbridge chip. The FSB is the main channel for the CPU to exchange data with the outside world, so the FSB's ability to transfer data plays a big role in the overall performance of the computer. Without a fast enough FSB, even the strongest CPU will not be able to significantly increase the overall speed of the computer. The maximum bandwidth of data transmission depends on the width of all simultaneously transmitted data and transmission frequency, i.e., data bandwidth = (bus frequency × data bit width) ÷ 8. Currently, the front-end bus frequency that can be achieved on the PC has 266MHz, 333MHz, 400MHz, 533MHz, 800MHz several kinds, up to 1066MHz. the greater the frequency of the front-end bus, which represents the data transmission between CPU The higher the front side bus frequency, the greater the data transmission capacity between the CPU and the Northbridge chip, and the more fully realize the function of the CPU. With the fast development of CPU technology and the rapid increase of computing speed, a large enough front side bus can guarantee enough data supply to the CPU, while a lower front side bus will not be able to supply enough data to the CPU, which will limit the performance of the CPU and become a bottleneck of the system.
The concept of external frequency is based on the oscillation speed of digital pulse signals, that is, 100MHz external frequency refers to the digital pulse signals oscillating 10,000,000 times per second. The external frequency specifically refers to the bus speed between the CPU and the chipset. External frequency is the speed of synchronous operation between the CPU and the motherboard, and the vast majority of current computer systems in the external frequency, but also the speed of synchronous operation between the memory and the motherboard, in this way, it can be understood as the external frequency of the CPU is directly connected to the memory, to achieve the synchronous operation of the two states.
Before the 486, the main frequency of the CPU was still in a lower stage, and the main frequency of the CPU was generally equal to the external frequency. And after the appearance of the 486, because the CPU operating frequency continues to increase, while some other devices of the PC (such as plug-in cards, hard disk, etc.) but by the limitations of the process, can not withstand a higher frequency, thus limiting the further increase in the frequency of the CPU. Therefore, the emergence of multiplier technology, the technology can make the CPU internal operating frequency into a multiple of the external frequency, so as to enhance the multiplier frequency and achieve the purpose of raising the main frequency. Multiplier technology is to make the external device can work in a lower frequency (this lower frequency is the external frequency), but does not limit the impact of the CPU's own operating frequency (mains frequency), because the CPU mains frequency is a multiple of the external frequency.
Again, the two concepts of front-end bus and external frequency are easily confused, the main reason is that in the previous a long time (mainly before the appearance of the Pentium4 and just appeared when the Pentium4), the front-end bus frequency and the external frequency is the same, so often directly called the front-end bus for the external frequency, and ultimately lead to such a misunderstanding. With the development of computer technology, it was found that the front bus frequency needed to be higher than the external frequency, so QDR (QuadDateRate) technology (4 times concurrent), or other similar techniques were used to achieve this. The principle of these technologies is similar to AGP's 2X or 4X, which make the front-end bus frequency become 2X, 4X or even higher than the external frequency, and since then the difference between the front-end bus and the external frequency has only begun to be emphasized. When the external frequency is still 133MHZ, the front bus speed increases 4 times to become 133X4=533MHZ, and when the external frequency goes up to 200MHZ, the front bus becomes 800MHZ, so you will see the P4 of the 533 front bus and the P4 of the 800 front bus, and that's how it comes about.
In general, the main frequency (i.e., CPU frequency) and the front side bus frequency are based on the external frequency, the former is multiplied by the number of multiplier, the latter is multiplied by 2/4/8, except that the latter multiplied by the coefficient can not be called a multiplier, is due to the use of the QDR (QuadDateRate) technology, or other similar technology to achieve. And all three were a concept in the early days.
As far as memory is concerned, there are generally three frequencies to describe it - core frequency/clock frequency/data transfer rate. The data transfer rate is the frequency labeled on the memory stick, such as DDR333 and DDR400, and by default, the usual memory frequency refers to the data transfer rate. The core frequency of the memory is like the frequency of the CPU, which is inherent in itself, while the clock frequency is what we call the external frequency. For DDR, the ratio of the three is 1:1:2, and for DDR2, the ratio of the three is 1:2:4.
In the previous P3, with a 133 external frequency, the core frequency of the memory was 133, the data transfer rate was also 133, and the front-side bus of the CPU was 133, which was the same thing. Now the P4 CPU, at an external frequency of 133, the front-side bus reaches 533MHZ (× 4), and the memory frequency is 266 (DDR266). Problems arise, the front-end bus is the bridge between the CPU and the memory connection, P4 this time the front-end bus reached 533 high, while the memory is only 266 speed, the memory than the CPU front-end bus half slower than the theoretical CPU half of the time to wait for the memory to pass the data over in order to deal with the data, equal to the memory dragged the CPU's back legs. Such a situation does exist, 845 and 848 motherboards are such. So put forward a dual-channel memory concept, two memory using two channels to work together, together to provide data, is equal to the speed and doubled, two DDR266 will have 266X2 = 533 speed, just P4CPU's front-side bus speed, there is no drag behind the problem. When the external frequency is raised to 200, the CPU front-side bus becomes 800, and two DDR400 memories form a dual-channel, and the memory transfer speed is also 800. So to P4 play well, must use dual-channel memory, 865 and above motherboards provide this function. But the 845 and 848 motherboards do not have dual-channel memory.