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    2021-10-21 17:40:23
    What are Motherboards?


    Ⅰ Introduction
    Ⅱ Motherboard structure 1.Chipset
    2.North Bridge and South Bridge
    3.BIOS chip
    4.Main interfaces

    Ⅰ Introduction

    The motherboard, also called the mainboard, is installed in the main computer box. It is one of the most basic and important components of the computer and plays a pivotal role in the entire computer system. The manufacturing quality of the motherboard determines the stability of the hardware system. The motherboard is closely related to the CPU. Every major upgrade of the CPU will inevitably lead to the replacement of the motherboard. The motherboard is the core of the computer hardware system and the largest printed circuit board in the main box.

    The main function of the motherboard is to transmit various electronic signals, and some chips are also responsible for the preliminary processing of some peripheral data. The various components in the computer host are connected through the motherboard. The control of the system memory, storage devices, and other I/O devices during the normal operation of the computer must be completed through the motherboard. Whether the computer performance can be fully utilized, whether the hardware functions are sufficient, and the compatibility of the hardware, etc., all depend on the design of the motherboard. The pros and cons of the motherboard determine to a certain extent the overall performance, service life, and function expansion capabilities of a computer.



    The motherboard uses an open structure. Most of the motherboards have 6-15 expansion slots for the control cards (adapters) of PC peripherals to plugin. By replacing these plug-in cards, the corresponding subsystems of the microcomputer can be partially upgraded, so that manufacturers and users have greater flexibility in configuring models. In short, the motherboard plays a pivotal role in the entire microcomputer system. It can be said that the type and grade of the motherboard determine the type and grade of the entire microcomputer system, and the performance of the motherboard affects the performance of the entire microcomputer system.

    Ⅱ Motherboard structure

    The so-called motherboard structure is a general standard established according to the layout, size, shape, and power supply specifications of the components on the motherboard, which all motherboard manufacturers must follow. The motherboard structure is divided into AT, Baby-AT, ATX, Micro ATX, LPX, NLX, Flex ATX, E-ATX, WATX, and BTX. Among them, AT and Baby-AT are old motherboard structures many years ago and have been eliminated; while LPX, NLX, and Flex ATX are variants of ATX; E-ATX and W-ATX are mostly used in server/workstation motherboards; ATX is the most common motherboard structure on the market. There are many expansion slots, the number of PCI slots is 4-6, most motherboards use this structure; Micro ATX, also known as Mini ATX, is a simplified version of the ATX structure, which is often called "small board", the number of PCI slots is 3 or less, mostly used in branded machines and equipped with small chassis; BTX is the latest generation of motherboard structure developed by Intel, but it was abandoned before it became popular.

    mainboard components.jpg

    motherboard components


    The core of the motherboard is the motherboard chipset, which determines the specifications, performance, and general functions of the motherboard. We usually say "865PE motherboard”, 865PE refers to the motherboard chipset. If the CPU is the heart of the entire computer system, then the chipset will be the trunk of the entire system. For the motherboard, the chipset almost determines the function of this motherboard, which in turn affects the performance of the entire computer system. The chipset is the soul of the motherboard. This is because the CPU has a wide range of models and types and different functional characteristics. If the chipset cannot work well with the CPU, it will seriously affect the overall performance of the computer, or even fail to work normally.

    2.North Bridge and South Bridge

    In the traditional chipset structure, the South Bridge and the North Bridge have been matched, and their specific positions can be found on the motherboard. Generally, we can find a heat sink near the CPU socket on the motherboard, and the northbridge chip is below. The South Bridge chip is generally far away from the CPU, often exposed next to the PC I slot and is relatively large. The north bridge chip is a system control chip, which is mainly responsible for data exchange between the CPU, memory, and graphics card. It plays a leading role in the chipset composed of the southbridge chip and controls some high-speed devices, such as CPU, Host bus, etc.

    What CPU the motherboard supports, how many graphics cards it supports for AGP, and what frequency of memory it supports are all determined by the North bridge chip. The northbridge often has a higher operating frequency, so the heat generation is quite high. The south bridge mainly determines the functions of the mainrboard. The various interfaces on the motherboard, PS/2 mouse control, USB control, PCI bus IDE, and other chips on the motherboard are all controlled by the South Bridge chip. With the continuous development of the PC architecture, the functions of the north bridge are now gradually included by the CPU, and its structure is continuously simplified and even no longer exists in the chipset.

    3.BIOS chip

    BIOS (Basic Input/ Output System) is actually a set of programs that are solidified into the computer to provide the computer with the lowest level and most direct hardware control. It is the hub between the software program and the hardware device. The BIOS a "converter" or interface is between the hardware and the software program, which is responsible for solving the immediate requirements of the hardware, and executes it according to the operating requirements of the software on the hardware. From a functional point of view, BIOS mainly includes two parts:

    (1) Self-check and initialization

    Self-check and initialization are responsible for starting the computer, and there are 3 parts:

    Power on self test (POST) is used to test the hardware when the computer is just turned on to check whether the computer is in good condition. Usually, a complete POST self-test will include testing the CPU, 640K basic memory, 1M or more extended memory, ROM, motherboard, CMOS memory, serial and parallel ports, graphics card, soft and hard disk subsystem, and keyboard. Once problems are found in the self-test, the system will give a prompt message or buzzer warning.

    Initialization includes creating interrupt vectors, setting registers, initializing and testing some external devices, etc. The most important part is the BIOS settings, which are mainly the parameters of the hardware settings. When the computer starts, it will read these parameters, and the actual hardware settings are compared. If they do not match, it will affect the startup of the system.

    The bootloader is used to boot DOS or other operating systems. BIOS first reads the boot record from the start sector of the floppy disk or hard disk. If it is not found, it will show that there is no boot device. If it finds the boot record, it will transfer the control of the computer to the boot record, and the boot record will transfer to the operating system Load the computer. After the computer starts successfully, this part of the BIOS task is completed.

    (2) Program service processing and hardware interrupt processing

    These two parts are two independent contents, but they are closely related in use. Program service handlers mainly serve applications and operating systems. These services are mainly related to input and output devices, such as reading disks and outputting files to printers. In order to complete these operations, B1OS must directly deal with the computer's I/O devices. It sends commands through ports, transmits data to various external devices, and receives data from them, so that the program can be separated from specific hardware operations, and hardware interrupt processing. Then the PC hardware requirements are handled separately, so the two parts are software and hardware services respectively, and they are combined to make the computer system run normally.

    4.Main interfaces

    Hard disk interface: Hard disk interface can be divided into IDE interface and SATA interface. On older motherboards, two more IDE ports are integrated. Usually, the IDE ports are located under the PCI slot, and spatially they are perpendicular to the memory slot (there are also horizontal ones). On the new motherboards, IDE interfaces are mostly reduced, or even none, and replaced by SATA interfaces.

    Floppy drive interface: it is used to connect to the floppy drive. It is mostly located next to the IDE interface, which is slightly shorter than the IDE interface. Because it is 34-pin, the data cable is also slightly narrower.

    COM interface (serial port): Most motherboards provide two COM interfaces, namely COM1 and COM2, which are used to connect serial mice and external modems. The I/O address of the COM1 interface is 03F8h-03FFh, and the interrupt number is IRQ4; the I/O address of the COM2 interface is 02F8h-02FFh, and the interrupt number is IRQ3.

    PS/2 interface: The function of the PS/2 interface can only be used to connect a keyboard and mouse. In general, the mouse interface is green and the keyboard interface is purple. The transmission rate of the PS/2 interface is slightly faster than that of the COM interface, but after so many years of use, most motherboards are still equipped with this interface, but there are fewer and fewer mice and keyboards supporting this interface. Most peripheral manufacturers no longer Introduced peripheral products based on this interface, and more often introduced peripheral products with a USB interface.

    USB interface: The USB interface is the most popular interface today. It can support up to 127 peripherals and can be independently powered. Its application is very wide. The USB interface can get 500mA current from the motherboard, supports hot-plugging, and truly plug and play. The transmission rate of high-speed peripherals is 12Mbps, and the transmission rate of low-speed peripherals is 1.5Mbps. In addition, the maximum transfer rate of the USB 2.0 standard can reach 480Mbps. USB 3.0 has appeared and popularized in motherboards.

    LPT port (parallel port): it is generally used to connect a printer or scanner. The default interrupt number is IRQ7, which uses a 25-pin DB-25 connector. There are three main working modes of parallel port:

    1. SPP standard working mode. SPP data is half-duplex unidirectional transmission, with a slower transmission rate of only 15Kbps, but it is widely used and generally set as the default working mode.

    2. EPP enhanced working mode. EPP uses two-way half-duplex data transmission, and its transmission rate is much higher than SPP, up to 2Mbps. Many peripherals have used this working mode.

    3. ECP extended working mode. ECP adopts two-way full-duplex data transmission, and the transmission rate is higher than EPP, but there are not many devices supported. Printers and scanners using the LPT interface are basically very few, mostly printers and scanners using the USB interface.

    MIDI interface: The MIDI interface of the sound card and the joystick interface are shared. The two pins in the interface are used to transmit MIDI signals and can be connected to various MIDI devices.

    SATA interface: The full name of SATA is Serial Advanced Technology Attachment (a serial hardware drive interface based on industry standards). The SATA specification increases the theoretical value of the external transfer rate of the hard disk to 150MB/s, which is 50% higher than the PATA standard ATA/100 and about 13% higher than ATA/133.

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