PC Interpretation 4: getting to know the North-South Bridge

Some time ago I found some books on CPU interfaces, thinking that programmers can write programs and even become system analysts as long as they understand the CPU interfaces and CPU instruction sets, later, I thought it was not enough. I checked the connection topology of various computer components to find out that the north-south bridge is quite important.

Computer technology is growing at an astonishing speed. Both the software structure and the hardware structure are constantly changing and developing, so that our computer performance has been growing at a high speed. At the same time, there is also a problem, that is, when we learn about the hardware, it is constantly changing and cannot be fully grasped. But in any case, we should first extract a static surface and then look at the derived situation. It may be clear.

The figure above shows a mature structure. At first glance, it overturned some of our previous concepts. Previously, we thought that the CPU was directly connected to the primary memory (RAM). Now, we can see that the CPU is only connected to the North Bridge. The so-called North Bridge is the North Bridge, haha. Like a bridge, when someone else receives it, he can use route forwarding to help them communicate with each other.

We can see that there are CPU, Ram, cache, and AGP graphics cards connected to the North Bridge (graphics card and then directly connected to the CRT Display) and PCI bus, A very important device connected to the PCI bus is nanqiao. The Southern bridge is connected to some relatively low-speed I/O interface devices and traditional ISA bus. Low-speed I/O devices mainly include the keyboard, mouse, IDE interface hard disk, CD, red purple USB, and the old serial parallel interface.

The reason for this layout is that we divide the devices into two categories. One is that the devices with relatively large data interactions and high speed, such as CPU, primary storage, cache, and AGP display. These devices bridge together through the North bridge so that they can communicate quickly.

Relatively speaking, the devices on the Southern bridge are relatively low-speed devices, such as hard disks and nic Io devices. To access the I/O space of these devices, the CPU must first go to the North Bridge and then "Route" to the south bridge. The South Bridge is also a bridge, and the south bridge routes the data to the corresponding device.

It can be seen that a simple command of the CPU, such as reading data from the hard disk sector, needs to go through the North Bridge, south bridge, and then to the IDE Controller Integrated on the south bridge to the IDE interface and finally to the IDE device. Programmers only give CPU commands to read and write data, while data (commands are also data) transmission needs to pass through the bus, bridge, interface these devices. By understanding this, we can better understand the bottlenecks of the system and the performance breakthroughs of new hardware devices.

For example, if we may download large files such as movies on the LAN, we can analyze them if they are not fast enough. It depends on the speed of each data transmission segment. In the download service, the network card is first transmitted from a computer's network card device to another computer's network card device. The PC's network card is generally on the south bridge. Therefore, the data is transferred from the network card to the south bridge chip, then to the North Bridge, and finally to the memory, and then back from the memory to the North Bridge and then to the south bridge, and then to the IDE hard disk, during this period, it takes two times to cross the north-south bridge between the PCI bus, the highest transmission speed of the PCI bus is 133 m, and it is shared by all devices on the south bridge.

So now, with the emergence of high-speed IO devices, such as usb3.0, the PCI connection between the North and South bridges has become the bottleneck of the system, so we can see that intel, AMD and other north-south bridge chip manufacturers began to make major improvements to their architecture, providing a higher connection speed between the North and South bridges. If you are interested, you can ask Baidu to find out.

Of course, here we only talk about their connection relationship, And we know a little bit about it. We also need to continue to study their communication solutions later. We know the IP addresses used for network communication, so what is the use of device communication in the computer? What is a design? Please check and ask.