Northbridge chip is the most important part of the motherboard chipset, also known as the host bridge. Generally speaking, the name of the chipset is named after the name of the North Bridge chip. For example, the northbridge chip of Intel 845E chipset is 82845E, and the northbridge chip of 875P chipset is 82875P. Northbridge chip is responsible for contacting CPU, controlling the transmission of memory and AGP data in Northbridge, and providing support for CPU type and main frequency, system front-end bus frequency and memory type (SDRAM, DDR SDRAM and RDRAM, etc.). ) and maximum capacity, AGP slot, ECC error correction, etc. The Northbridge chip of the integrated chipset also integrates a display core. Northbridge chip is the closest chip to CPU on the motherboard, mainly because the communication between Northbridge chip and processor is the closest, and in order to improve communication performance, the transmission distance is shortened. Because the data processing capacity of the Northbridge chip is very large, and the heat generation is also increasing, the current Northbridge chips are covered with heat sinks to enhance the heat dissipation of the Northbridge chip, and some motherboards' Northbridge chips also cooperate with fans to dissipate heat. Because the main function of the Northbridge chip is to control the memory, and the memory standard changes as frequently as the processor, the Northbridge chips of different chipsets are definitely different. Of course, this does not mean that the adopted memory technology is completely different, but there must be some differences between the Northbridge chips of different chipsets.

As the released AMD K8 Core CPU integrates the memory controller into the CPU, the Northbridge chip supporting K8 chipset becomes much simpler, and even a single-chip chipset structure can be adopted. This may be a general trend, and the functions of the North Bridge chip will be gradually simplified. In order to simplify the main board structure and improve the integration of the motherboard, perhaps the mainstream chipset will probably become a single-chip form with the integration of the North Bridge and the South Bridge (in fact, SIS has already released many single-chip chipsets).

Because each chipset product corresponds to a corresponding Northbridge chip, the number of Northbridge chips is very large. According to the different platforms, the mainstream Northbridge chips have the following products (excluding the old products, only the Intel chipset with the most users will be described in detail).

Southbridge

South bridge chip is an important part of motherboard chipset, which is generally located under CPU slot and near PCI slot on motherboard. This layout is based on the fact that there are many I/O buses connected to it, and being far away from the processor is beneficial to wiring. Compared with the north bridge chip, its data processing ability is not great, so the south bridge chip generally does not cover the heat sink. The south bridge chip is not directly connected to the processor, but connected to the north bridge chip in a certain way (chipsets of different manufacturers are different, such as Intel Hub architecture of Intel and multi-threading "fun" of SIS).

The South Bridge chip is responsible for the communication among I/O buses such as PCI bus, USB, LAN, ATA, SATA, audio controller, keyboard controller, real-time clock controller and advanced power management. These technologies are generally stable, so the South Bridge chip may be the same in different chipsets, but the difference is only the North Bridge chip. Therefore, the number of north bridge chips in the motherboard chipset is far more than that of south bridge chips. For example, early Intel chipsets with different architectures, such as 430TX of Socket 7 and 440LX of Slot 1, all used 823 17AB for their South Bridge chips. In recent two years, ICH7 or ICH7R southbridge chips have been used in Intel945 series chipsets, but they can also be matched with ICH6 southbridge chips. What's more, the North-South Bridge used in a few products produced by some motherboard manufacturers is the products of different chipset companies.

The development direction of Southbridge chip is mainly to integrate more functions, such as network card, RAID, IEEE 1394 and even WI-FI wireless network.

main board structure

Because the motherboard is the connection carrier of various devices in the computer, and these devices are different, and the motherboard itself also has chipset, various I/O control chips, expansion slots, expansion interfaces, power sockets and other components, it is necessary to formulate a standard to coordinate the relationship between various devices. The so-called main board structure is a general standard based on the layout, arrangement, size, shape and power specification of all components on the motherboard, which all motherboard manufacturers must follow.

Main board structure is divided into AT, Baby-AT, ATX, Micro ATX, LPX, NLX, Flex ATX, EATX, WATX and BTX. Among them, AT and Baby-AT were old main board structure many years ago, and now they have been eliminated; LPX, NLX and Flex ATX are all variants of ATX, which are more common in foreign brand machines than in China. EATX and WATX are mostly used for server/workstation motherboards; ATX is the most common main board structure in the market at present, with many expansion slots and 4-6 PCI slots. Most motherboards adopt this structure. Miniature ATX, also known as Miniature ATX, is a simplified version of ATX structure and is often called "small board". There are few expansion slots, and the number of PCI slots is three or less, which are mostly used for brand machines with small chassis. BTX is the latest generation of main board structure developed by Intel.

Car audio effect

On-board sound effect refers to the model or type of sound card chip integrated with the motherboard.

Sound card is one of the main equipment of multimedia computer. Now sound cards are generally divided into onboard sound cards and independent sound cards. Early computers didn't have an onboard sound card, so the sound of the computer was realized by an independent sound card. With the improvement of motherboard integration and the increasingly powerful CPU performance, as well as the consideration of motherboard manufacturers to reduce the purchase cost of users, onboard sound cards appear in more and more motherboards. At present, the onboard sound card has almost become the standard configuration of the motherboard, and there are fewer motherboards without onboard sound card.

ALC650 sound card chip on board

The onboard sound card is generally divided into soft sound card and hard sound card. The distinction between software and hardware here refers to whether the onboard sound card has the main processing chip of the sound card. Generally, a soft sound card has no main processing chip, but only a decoding chip, which replaces the function of the main processing chip of the sound card through CPU operation. The onboard hard sound card has a main processing chip, so many sound processing jobs no longer need CPU participation.

AC'97

The full name of AC'97 is Audio CODEC'97, which is an audio circuit system standard jointly developed by Intel, Yamaha and other manufacturers. It is not a real sound card, but a standard. The latest version has reached 2.3. Most of the codecs of sound cards that can be seen on the market now conform to AC'97 standard. Manufacturers are also used to measuring sound cards according to coding and decoding standards, so many motherboard products are called AC'97 sound cards, no matter what sound card chips and types are used.

High definition audio

HD Audio is the abbreviation of High Definition Audio, formerly known as Azalia, which is a new generation audio specification jointly launched by Intel and Dolby. At present, it is mainly adopted by ICH6 series south bridge chips of Intel 9 15/925 series chipsets.

HD Audio is formulated to replace the current popular AC'97 audio specification, which has many similarities with AC'97. To some extent, it can be said to be an enhanced version of AC'97, but it cannot meet the AC'97 standard in backward compatibility. It provides a new connection bus based on AC'97, which supports higher quality audio and more functions. Similar to AC'97 audio solution, HD Audio is also a mixed audio specification, which is integrated in ICH6 chip (except codec part). Compared with the current AC'97, high-definition audio has the characteristics of large data transmission bandwidth, high audio playback accuracy, support for multi-channel array microphone audio input, lower CPU occupancy, and universal underlying driver.

What's particularly interesting is that HD audio has a very humanized design. High-definition audio supports device awareness and interface definition functions, that is, all input and output interfaces can automatically sense device access and give prompts, and the functions of each interface can be set at will. This function can not only determine which port it is plugged in, but also define a function for the interface. For example, when a user plugs a microphone into an audio output interface, HD Audio can detect that the interface has a device connection, and can automatically detect the device type, define the interface as a microphone input interface, and change the original interface properties. From this perspective, connecting speakers, headphones and MIC is as simple as connecting USB devices. You can switch the interface with a few mouse clicks on the control panel. Even for complex multi-channel speakers, novice users can "plug and play".

Advantages and disadvantages of onboard sound card

Because the onboard soft sound card has no sound card main processing chip, it will occupy some CPU resources when processing audio data, which will slightly affect the system performance when the CPU frequency is not too high. At present, the main frequency of CPU has been calculated by GHz, but the amount of audio data processing has not increased much. Compared with the previous CPU, the CPU resource occupation is greatly reduced, and the impact on system performance can be ignored, almost negligible.

The problem of "sound quality" is also a major drawback of the onboard soft sound card, especially the low signal-to-noise ratio. In fact, this problem is not caused by the defects of the onboard soft sound card in audio processing, mainly because the motherboard manufacturers are unreasonable in wiring when designing the onboard sound card, and the materials and workmanship are too cost-saving.

For the onboard hard sound card, the above two problems basically do not exist, and its performance can basically approach and reach the general independent sound card, which can completely meet the needs of ordinary home users.

The biggest advantage of integrated sound card is cost performance. With the continuous improvement of sound card driver, the improvement of motherboard manufacturer's design ability, the improvement of onboard sound card chip performance and the decline of price, onboard sound card is more and more recognized by users.

The disadvantage of onboard sound card is the advantage of independent sound card, and the disadvantage of independent sound card is the advantage of onboard sound card. Independent sound cards range from tens of dollars to thousands of dollars. In performance, the integrated sound card is not inferior to the low-end independent sound card at all, and the integrated sound card has more advantages in cost performance. In the low-end market, integrated sound card is a good choice for users who are pursuing price.

Onboard network card

The motherboard network card chip refers to the motherboard integrated network card chip that integrates network functions. Correspondingly, there is also a corresponding network card interface (RJ-45) on the backplane of the motherboard, which is generally located near the audio interface or USB interface.

On-board RTL8 100B network card chip

In the past, because there was little broadband Internet access, most of them were dial-up Internet access, and the network card was not an indispensable part of the computer. Few motherboards have onboard network card chips before, so if you want to use network cards, you can only use expansion cards. Nowadays, with the popularity of broadband Internet access, network cards have gradually become one of the basic accessories of computers, and more and more motherboards are equipped with network card chips.

In the case of using the same network card chip, there is no difference in performance between the onboard network card and the independent network card, and compared with the independent network card, the onboard network card also has unique advantages. The first is to reduce the purchase cost of users. For example, there are more and more motherboards with Gigabit network cards on board, but it costs several hundred yuan to buy an independent Gigabit network card. Secondly, it can save system expansion resources and does not occupy PCI slots or USB interfaces that independent network cards need to occupy; Thirdly, it can achieve good compatibility and stability, and it is not easy to have the problem that the independent network card is incompatible with the motherboard or conflicts with other equipment resources.

On-board network card chips can be divided into 10/ 100Mbps adaptive network card and gigabit network card according to speed, ordinary network card and wireless network card according to network connection, and network card chips with built-in chipset (South Bridge chips of some chipsets, such as SIS963) and independent network card chips attached to the motherboard (such as Realtek 8 139 series) according to chip types. Some high-end home motherboards and server motherboards also provide dual onboard network cards.

The main manufacturers of onboard network card chips are Intel, 3Com, Realtek, VIA, Marvell, etc.

PCI Express slot

PCI-Express is the latest bus and interface standard. Its original name is "3GIO", which was put forward by Intel Corporation. Obviously, what Intel means is that it represents the next generation I/O interface standard. After being certified by PCI-SIG, it was renamed as "PCI-Express". This new standard will completely replace the existing PCI and AGP, and finally realize the unification of bus standards. Its main advantage is its high data transmission rate, which can reach above 10GB/s at present, and its development potential is considerable. PCI Express also has many specifications, from PCI Express 1X to PCI Express 16X, which can meet the needs of low-speed equipment and high-speed equipment at present and in the future. Intel's i9 15 and i925 series chipsets can support PCI Express. Of course, it will take a long time to completely replace PCI and AGP, just like when PCI replaces ISA, there will be a transition process.

PCI Express (hereinafter referred to as PCI-E) adopts the popular point-to-point serial connection in the industry. Compared with PCI and earlier computer bus parallel architecture, each device has its own dedicated connection, and it is not necessary to request bandwidth from the whole bus. The data transmission rate can be increased to a very high frequency, reaching a high bandwidth that PCI cannot provide. Compared with the traditional PCI bus, which can only realize one-way transmission in a single time period, the dual simplex connection of PCI-E can provide higher transmission rate and quality, and the difference between them is similar to half-duplex and full-duplex.

Interfaces of PCI-E vary according to the bus bit width, including X 1, X4, X8 and X 16. The internal interface will use X2 mode instead of slot mode. PCI-E specification is connected from 1 channel to 32 channels, which is very extensible and can meet the different requirements of different system devices for data transmission bandwidth. In addition, the shorter PCI-E card can be inserted into the longer PCI-E slot, and the PCI-E interface can also support hot plug, which is also a big leap. The 250MB/ s transmission speed of PCI-E X 1 can meet the data transmission bandwidth requirements of mainstream audio chips, network card chips and storage devices, but it is far from meeting the data transmission bandwidth requirements of graphics chips. Therefore, the bit width of PCI-E interface used to replace AGP interface is X 16, which can provide a bandwidth of 5 GB/s. Even if there is coding loss, it can still provide an actual bandwidth of about 4GB/s, far exceeding the bandwidth of 2. 1GB/s of AGP 8X.

Although the PCI-E technical specification allows the realization of X 1(250MB/ s), X2, X4, X8, X 12, X 16 and X32 channel specifications, in the current form, PCI-E X 1 and PCI-EX/. In addition to providing extremely high data transmission bandwidth, PCI-E also uses serial data packets to transmit data, so each pin of PCI-E interface can get more bandwidth than the traditional I/O standard, which can reduce the production cost and volume of PCI-E equipment. In addition, PCI-E also supports advanced power management, hot plug, synchronous data transmission and bandwidth optimization of priority data transmission.

expansion interface

The expansion interface is an interface on the motherboard for connecting various external devices. Through these expansion interfaces, printers, external modems, scanners, flash drives, MP3 players, DC, DV, mobile hard disks, mobile phones, wordpads and other external devices can be connected to the computer. And the interconnection between computers can be realized through the expansion interface.

At present, the common expansion interfaces include serial port, parallel port, universal serial bus interface (USB) and IEEE 1394 interface.

serial interface

Serial interface, COM interface for short, is an extended interface using serial communication protocol. The serial port appears around 1980, and the data transmission rate is115 kbps to 230 kbps. Serial port is generally used to connect mouse and external modem, old camera and tablet. At present, some new motherboards have begun to cancel this interface.

parallel interface

Parallel interface, LPT interface for short, is an extended interface using parallel communication protocol. The data transmission rate of parallel port is 8 times faster than that of serial port, and the data transmission rate of standard parallel port is 1Mbps, which is generally used to connect printers and scanners. So the parallel port is also called the printing port.

In addition, both serial port and parallel port can be interconnected by direct cable connection, in which data can only be transmitted at low speed. The function and structure of serial port and parallel port of PC have not changed for many years. When using serial-parallel ports, in principle, each peripheral must insert an interface. If all interfaces are used, you can only add interfaces by adding cards. Serial port and parallel port are not only limited in speed, but also inconvenient to use, such as not supporting hot plug. With the popularization of USB interface, it is rarely used at present, and it will be eliminated with the promotion of BTX specification.

Universal serial bus

USB is the abbreviation of English universal serial bus, which means "universal serial bus" in Chinese. It is not a new bus standard, but an interface technology applied in PC field. USB was put forward by Intel, Compaq, IBM and Microsoft at the end of 1994. But it was not widely used until recently. Since June1994+065438+1October 1 1 released the USB version V 0.7, the USB version has developed for many years, and now it has developed to version 2.0, which has become a standard expansion interface in computers. At present, the mainboard mainly uses USB 1. 1 and USB2.0, and the USB versions are very compatible. USB uses a 4-pin plug as a standard plug, which can connect all peripherals in daisy chain, and can connect up to 127 external devices without losing bandwidth. USB needs the support of host hardware, operating system and peripherals to work. At present, the motherboard generally adopts a control chipset supporting USB function, and a USB interface socket is also installed on the motherboard. In addition to the socket on the backplane, a USB pin is reserved on the motherboard, which can be connected to the front of the chassis as a front USB interface for easy use (note that when wiring, you should read the motherboard manual carefully and connect it according to the diagram, and don't damage the equipment because of wrong connection). Moreover, USB interfaces can also be interconnected through special USB cables, and more interfaces can be extended through Hub. USB has the advantages of high transmission speed (USB 1. 1 is 12Mbps, and USB2.0 is 480Mbps), convenient use, hot plug support, flexible connection and independent power supply. It can connect mouse, keyboard, printer, scanner, camera, flash drive, MP3 player, cable modem, digital camera, mobile hard disk and external devices.

IEEE 1394

IEEE 1394, formerly known as Firewire, is a transmission interface developed by Apple Computer Company for high-speed data transmission in 1986, and was recognized by the American Institute of Electrical and Electronics Engineers in 1995 and became a formal standard. Now IEEE 1394, Firewire and i.LINK all refer to this standard. It is usually called IEEE 1394 in the field of PC and i.LINK in the field of consumer electronics, and it was first used in the Firewire of MAC. IEEE 1394 is also an efficient serial interface standard with powerful functions, stable performance and support for hot plug. IEEE 1394 One port can connect up to 63 devices, and the devices adopt tree or daisy chain topology.

IEEE 1394 standard defines two bus modes, namely backplane mode and cable mode. Backplane mode supports transmission rates of 12.5, 25 and 50Mbps; Wired mode supports transmission rates of 100, 200 and 400Mbps. At present, the latest IEEE 1394b standard can reach the transmission rate of 800Mbps. IEEE 1394 is a universal interface across PC and home appliance platforms, which is suitable for most products that need high-speed data transmission, such as high-speed external hard disk, CD-ROM, DVD-ROM, scanner, printer, digital camera, video camera and so on. IEEE 1394 is divided into 6-pin A-type interface with power supply function and 4-pin B-type interface without power supply function. A-type interface can be compatible with B-type through jumper, but B-type has no power supply ability after being converted into A-type. The 6-pin A-type interface is widely used in Apple's computers and peripherals, while the simplified 4-pin B-type interface is mostly used in consumer electronic products and PCs, requiring a separate power adapter. The IEEE 1394 interface can be directly connected as a network card, and more interfaces can be extended through the Hub. Motherboards without IEEE 1394 interface can also get this function by plugging in IEEE 1394 expansion cards.

The power supply circuit is an important part of the motherboard, and its function is to convert the current transmitted by the host power supply into voltage, convert the voltage into a core voltage value acceptable to the CPU, and make the CPU work normally, and shape and filter the current transmitted by the host power supply to filter out all kinds of clutter and interference signals, so as to ensure the stable work of the computer. The main part of the power supply circuit is generally located near the CPU slot of the motherboard.

Power supply circuit can be divided into linear power supply mode and switching power supply mode according to its working principle.

Linear power supply mode

This is the main board power supply mode many years ago, which is realized by changing the conduction degree of the transistor. The transistor is equivalent to a variable resistor and is connected in series in the power supply circuit. Because the variable resistor flows through the same current as the load, it consumes a lot of energy, which leads to the temperature rise and the voltage conversion efficiency is low. Especially in the power supply circuit that needs large current, linear power supply cannot be used. At present, this power supply mode has long been eliminated.

Switching power supply mode

This is a widely used power supply method at present. The PWM controller IC chip provides pulse width modulation and sends out pulse signals to turn on MOSFET 1 and MOSFET2 in turn. Chokes L0 and L 1 are used as energy storage inductors, and together with the connected capacitors, an LC filter circuit is formed.

Its working principle is: when the voltage at both ends of the load (such as the voltage required by CPU) is to be reduced, the external power supply charges the inductor through the switching action of MOSFET to reach the required rated voltage. When the voltage across the load rises, the external power supply is disconnected through the switching effect of MOSFET, and the inductor releases the energy just charged, and then the inductor becomes the power supply to continue to supply power to the load. With the consumption of energy stored in the inductor, the voltage across the load begins to decrease gradually, so it is necessary to charge the external power supply through the switching effect of MOSFET. By analogy, in the process of continuous charging and discharging, it will become a stable voltage and will never increase or decrease the voltage at both ends of the load. This is the biggest advantage of switching power supply. In addition, because the MOSFET works in the switching state, its internal resistance when turned on and leakage current when turned off are very small, so its own power consumption is very small, which avoids the problem that the resistor part of the linear power supply in series in the circuit consumes a lot of energy. This is also the working principle of the so-called "single-phase power supply circuit".

General single-phase power supply can provide the maximum current of 25A, but the commonly used CPU has already exceeded this figure. The power of P4 processor can reach 70-80W, and the working current even reaches 50A. Single-phase power supply can not provide enough reliable power, so now the power supply circuit design of motherboard adopts two-phase or even multi-phase design. (Figure 2) is a schematic diagram of a two-phase power supply. It is easy to understand that two single-phase circuits are connected in parallel, so it can provide double current supply, which is more than enough to meet the needs of the current CPU in theory. But the above is only pure theory, and many practical factors need to be added, such as the performance of switching elements and the resistance of conductors, which are all factors that affect Vcore. In practical application, there are efficiency problems in the power supply, and the electric energy will not be converted into 100%. Generally speaking, the consumed electric energy will be converted into heat and emitted, so any common regulated power supply will always be the hottest part of electrical appliances. It should be noted that the higher the temperature, the lower its efficiency. In this way, if the conversion efficiency of the circuit is not very high, then the circuit using two-phase power supply may not meet the needs of CPU, so there are three-phase or even more power supply circuits. However, it also brings the complexity of motherboard wiring. If the wiring design is unreasonable at this time, it will affect the stability of high frequency work and a series of problems will appear. At present, many mainstream motherboard products in the market use three-phase power supply circuit, which can provide enough power for CPU. However, due to the lack of circuit design, the stability of the motherboard is limited to some extent in extreme cases. If we want to solve this problem, we must make greater efforts in circuit design and wiring, and the cost will rise.

The reason why the power supply circuit adopts multiphase power supply is to provide more stable current. The pulse square wave signal sent from the control chip PWM is shaped into a DC-like current through the LC oscillating circuit. The high potential time of square wave is very short. The more phases, the closer the quasi-DC is to DC.

The power supply circuit plays a very important role in the performance and stability of the computer, and is an important performance parameter of the motherboard. When purchasing, you should choose products with excellent design and sufficient materials from mainstream manufacturers.