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The main building block of the computer

 L'élément constitutif principal de l'ordinateur | La carte mère

The main building block of the computer

Is the motherboard (in English "mainboard" or "motherboard", sometimes abbreviated as "mobo"). The motherboard is the base allowing the connection of all the essential elements of the computer.

As the name suggests, the motherboard is a master card, taking the form of a large printed circuit with connectors for expansion cards, memory modules, the processor, etc.

There are several ways to characterize a motherboard, in particular, according to the following characteristics:

  • The size factor
  • The chipset
  • Type of processor socket
  • Input-output connectors

The size factor:

The term “size factor” (or form factor) is generally used to designate the geometry, dimensions, arrangement and electrical characteristics of the motherboard.

The chipset:

  • The chipset (translate set of components or set of circuits) is an electronic circuit responsible for coordinating the exchange of data between the various components of the computer (processor, memory ...). Since the chipset is integrated into the motherboard, it is important to choose a motherboard incorporating a recent chipset in order to maximize the possibilities of the scalability of the computer.
  • Some chipset sometimes includes a graphics chip or an audio chip, which means that it is not necessary to install a graphics card or a sound card. However, it is sometimes advisable to deactivate them (when possible) in the BIOS Setup and install quality expansion cards in the slots provided.

CMOS clock and battery:

  • The real-time clock (denoted RTC, for Real-Time Clock) is a circuit responsible for synchronizing system signals. It consists of a crystal which, by vibrating, gives impulses (called clock ticks) in order to clock the system. Called clock frequency (expressed in MHz) the number of crystal vibrations per second, that is to say, the number of clock ticks emitted per second. Information is increased at every frequency of processing the system.

  • When the computer is turned off, the power stops supplying power to the motherboard. When the computer is reconnected, the system is always on time. An electronic circuit, called CMOS (Complementary Metal-Oxide Semiconductor, sometimes called BIOS CMOS), stores certain information on the system, such as time system date, and some essential system parameters.

  • The CMOS is continuously powered by a battery (in button cell format) or a battery located on the motherboard. Thus, information about the hardware installed in the computer (such as the number of tracks, sectors of each hard drive) is kept in the CMOS. Since CMOS is slow memory, some systems sometimes copy the contents of CMOS into RAM (fast memory), the term "memory shadow" is used to describe this process of copying into RAM.

  • CMOS has made it possible to put complementary channels on the same chip. Compared to TTL or TTLS, CMOS is much slower, but on the other hand consumes infinitely less energy, hence its use in computer clocks, which are powered by batteries. The term CMOS is sometimes mistakenly used to refer to the clock on computers.

When the system time is regularly reset, or the clock is delayed, it is usually enough to change the battery!


  • The BIOS (Basic Input / Output System) is the basic program serving as an interface between the operating system and the motherboard. The BIOS is stored in a ROM (read-only memory, that is to say, a read-only memory), so it uses the data contained in the CMOS to know the hardware configuration of the system.

  • It is possible to configure the BIOS through an interface (called BIOS Setup, translate BIOS configuration) accessible at computer startup by pressing a key (usually the Delete key. In reality the BIOS Setup is only used for an interface for configuration, data is stored in CMOS. For more information, please refer to your motherboard manual).

  • “Complementary metal-oxide-semiconductor” is a technology for manufacturing transistors, preceded by many others, such as TTL (“Transistor-transistor-logic”), TTLS (TTL Schottky) (faster), or again NMOS (negative channel) and PMOS (positive channel).

Processor support:

  • The processor (CPU, for Central Processing Unit, or Central Processing Unit) is the brain of the computer. It makes it possible to manipulate digital information, that is to say, information encoded in binary form, and to execute the instructions stored in memory.

  • The first invention of the processor in 1971. It was a 4-bit computing unit, clocked at 108 kHz. Since then, the power of microprocessors has increased exponentially. So what are these little pieces of silicon that run our computers?


  • The processor (denoted CPU, for Central Processing Unit) is an electronic circuit clocked to the rhythm of an internal clock, thanks to a quartz crystal which, subjected to an electric current, sends pulses, called "top". The clock frequency (also called a cycle, corresponding to the number of pulses per second, is expressed in Hertz (Hz).

For example, a 200 MHz computer has a clock that sends 200,000,000 beats per second. The clock frequency is generally a multiple of the system frequency (FSB, Front-Side Bus), i.e. a multiple of the frequency of the motherboard

  • At each clock tick, the processor performs an action, corresponding to instruction or part of an instruction. The indicator called CPI (Cycles Per Instruction) is used to represent the average number of clock cycles required to execute an instruction on a microprocessor.

The power of the processor can thus be characterized by the number of instructions it is able to process per second. The unit used is MIPS (Millions of Instructions Per Second) corresponding to the processor frequency that the CPI divides.


An instruction is a basic operation that the processor can perform.
The instructions are stored in the main memory, for processing by the processor. An instruction is made up of two fields :

  • The operation code, representing the action that the processor must perform;
  • The operand code, defining the parameters of the action. The operand code depends on the operation. It can be a piece of data or a memory address.

The motherboard has a slot (sometimes several in the case of multi-processor motherboards) to accommodate the processor, called the processor socket.

There are two categories of media:

  • Slot (in French slot): it is a rectangular connector in which we insert the processor vertically
  • Socket (in French socket): it is a square connector with a large number of small connectors on which the processor is directly plugged

Within these two large families, there are different versions of the support, depending on the type of processor. It is essential, whatever the support, to gently connect the processor so as not to bend any of its pins (it has several hundred).

To facilitate its insertion, support called ZIF (Zero Insertion Force) has been created. ZIF sockets have a small lever, which, when raised, allows the processor to be inserted without any pressure and, when lowered, keeps the processor on its socket.

The processor generally has a key, materialized by a truncated corner or a colored mark, to be aligned with the corresponding mark on the support.

Since the processor radiates thermally, it is necessary to dissipate the heat to prevent its circuits from melting. This is the reason why it is generally surmounted by a heat sink (sometimes called cooler or radiator), composed of a metal with good thermal conduction (copper or aluminum), responsible for increasing the heat exchange surface. of the microprocessor.

The heat sink has a base in contact with the processor and fins to increase the heat exchange surface.

A fan generally accompanies the dissipator to improve the circulation of the air around the dissipator and to improve the heat exchange. The term “Ventirad” is thus sometimes used to designate the Fan   Radiator assembly.

The case fan is responsible for extracting hot air from the case and allowing fresh air from outside to enter it.

We hope you have benefited from this topic on the site  ==>  Computer Skills



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