- Generalities and schematic photo

- Shape factors and standards

- The components of the motherboard

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Juan Herrerías Rey

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What is... the motherboard?


With that they come next there ends the description of the elements of the badge; to see them in his original place, pulsate in "Generalities and schematic photo" in the Index. For several paragraphs additional information exists, in whose case is indicated along with the corresponding epigraph.


Slots for cards of expansion

There are a few plastic grooves with electrical connectors (slots) where there interfere the cards of expansion (videocard, of sound, of network...). According to the technology on which they are based they present a different external aspect, with different size and sometimes even in different color.

  • Grooves ISA: they are the most veteran, a legacy of the first times of the PC. They work to approximately 8 MHz and offer a maximum of 16 MB/s, sufficient to connect a modem or a sound card, but very little for a videocard. They measure approximately 14 cm and his color is usually a black; there exists a version even more ancient that measures only 8,5 cm.
  • Grooves Vesa Local Bus: a model of ephemeral life: it begun being used in the 486 and stopped being used in the first times of the Pentium. There are a development from ISA, who can offer approximately 160 MB/s to a 40 MHz maximum. They are the longest, approximately 22 cm, and his color is usually a black, sometimes with the end of the connector in brown or another color.
  • Grooves PCI: the current standard. They can give up to 132 MB/s to 33 MHz, what is sufficient for almost quite, except perhaps for some videocards 3D. They measure approximately 8,5 cm and generally they are white.
  • Grooves AGP: or rather groove, since he devotes himself to connect exclusively videocards 3D, therefore only there is usually one; also, its own structure prevents from being used for all the intentions, by what it is used like a help for the PCI. According to the functioning way it can offer 264 MB/s or even 528 Mb / century It Measures approximately 8 cm and she is separated enough from the rim of the badge.

The current badges tend to have more connectors possible PCI, supporting one or two connectors ISA because of compatibility with ancient cards and using AGP for the video.


Chips of cache memory of a badge 486

Cache memory

The following information is only a summary; to see the page dedicated exclusive to this element, pulsate here.

It is a question of a type of very rapid memory that is used of bridge between the microprocessor and the principal memory or RAM, in such a way that the most used information could be earlier, accelerating the yield of the computer, especially in applications ofimáticas.

It begun being implanted in the epoch of 386, without being of general use up to the arrival of the 486. His size has been always relatively limited (as maximum 1 MB), both for questions of design and for his high price, direct consequence of his big speed. This high price did that it even was going so far as to sell a considerable number of basic badges with false cache memories, something that fortunately at present is quite unusual.

Also it is known like external, secondary cache memory or of the second level (L2, level 2), to separate it from the internal cache memory or from the first level that all the microprocessors take from 486 (except 486SX and the first Celeron). His presentation changes very much: it can come in several chips or in the only chip, welded to the motherboard or in a special socket (for example of the type CELP) and even cannot be in the motherboard but to belong to the microprocessor, as in Pentium II and modern Celeron Mendocino.


External connectors of a badge ATX

External connectors

It is a question of the connectors for peripheral day pupils: keyboard, mouse, printer... In the badges Baby-AT the only thing that is in contact with the badge there are a few cables that her join with the connectors in themselves, who are located in the casing, except that of keyboard that yes is adherent to the proper badge. In the ATX the connectors are all grouped environment in that of keyboard and soldiers to the motherboard.

The principal connectors are:

Keyboard pin DOUGH

pin mini dough
Well for pin wide, proper DOUGH of the badges Baby-AT, or mini dough in badges ATX and many proprietary designs.
Parallel port
Parallel connector In few cases in which more of one exists, the second one would be LPT2. A connector is a female of approximately 38 mm, with 25 pines grouped in 2 tiers.
Ports series
(COM or RS232)
Connector series of 9 pines

Connector series of 25 pines
There are usually two, one strait of approximately 17 mm, with 9 pines (usually "COM1"), and another breadth of approximately 38 mm, with 25 pines (generally "COM2"), like the parallel but male, with the pines outside. Internally they are equal, only it changes the exterior connector; in the badges ATX they are usually both of 9 pines.
Port for mouse PS/2 pin mini dough In fact, a connector mini dough as that of keyboard; the name comes from his use in the computers PS/2 of IBM.
Games port Connector for joystick Or port for joystick or keyboard midi. Of size slightly major that the port series took in, of approximately 25 mm, with 15 pines grouped in 2 tiers.
Port VGA Connector VGA Including the modern SVGA, XGA... but not the CGA or EGA. Although the normal thing is that it is not integrated to the motherboard but to a card of expansion, we are going to describe it to avoid confusions: of approximately 17 mm, with 15 pines grouped in 3 tiers.
USB Connector USB In the most modern badges (not even in all the ATX); of narrow and rectangular, unmistakable form but of few utility for the time being.

At present the keyboards and mice tend to the mini dough or PS/2, and it is supposed that in a few years almost quite it will get connected to the USB, in a chain of peripheral connected to the same cable. Nevertheless, in my opinion we have left ports parallel and series for moment; not in vain we take more than fifteen years with them.


Connectors for hard disks and disk drive

Internal connectors

Under this denomination we include to the connectors for internal devices, as there could be the disk drive, the hard disk, the CD - ROM or the internal, and enclosed loudspeaker for the ports series, parallel and of joystick if the badge is not of format ATX.

In the ancient basic badges the support for these elements was realized by means of an auxiliary card, Input/Output call or simply of I/O, like that of the following photo; but already from the epoch of the 486 it became common to integrate the control chips of these devices in the motherboard, or at least the correspondents to hard disks and disk drive.

Detail of a card I/O with the most common internal connectors

Following the left photo to right, the first connector is the correspondent to the disk drive; it has 34 pines, and it is equivalent to that of minor size of the photo of the beginning of this paragraph; the following one is that of hard disk, which in the current badges is double (one for every channel IDE); it has 40 pines (sometimes only 39, since the pin 20 lacks utility) and any is equivalent to one of others two that appear in the top photo.

The rest of connectors (for ports series, parallel and joystick) can be straight day pupils (case of the badges ATX) or interns to connect a cable that ends in the corresponding adapter, which is the one that begins to show on the outside (case of the badges Baby-AT or those that use cards of I/O as that of the photo). As example, the following connector of the photo would be for the port of games or port for joystick, with 16 pines, port that at present is usually incorporated into the sound card; while the last connector, placed more to the right with only 10 pines, would be used to connect a cable for one of the ports series (another port series is precisely the connector that begins to show for the right side of the image).

In this class of connectors, it results from vital importance to know the position of the pin number 1, that 1 or an arrow will be indicated by means of a child, and that it will correspond to the end of the cable marked by a red line.


Finally, the internal loudspeaker, the leds (the bombillitas) for the hard disk, the indicator of ignition, the turbocharger (if it exists, in the modern badges it is completely in desuetude) and the switches of reset or stand - by connect all of them with thin colors cables to a series of jumpers whose position and typical of voltage they will be indicated in the manual of the badge and/or in the serigrafiado of the same one.


Electrical connector ATX Electrical connector Baby-AT

Electrical connector

It is where the cables get connected so that the motherboard receives the feeding provided by the source. In the badges Baby-AT the connectors are two, although they are one along with other, while in the ATX it is only.

When it is a question of connectors Baby-AT, they must get ready so that four black cables (2 of every connector), which are the grounds, stay in the center. The connector ATX usually has rectangular and trapezoidal forms alternated in some of the pines in such a way that it is impossible to mistake his orientation.

One of the advantages of the sources ATX is that they allow extinguished of the system for software; that is to say, that on having touched "to Extinguish the system" in Windows 95 the system: really it goes out!.




The battery of the computer, or more correctly the battery, is in charge of preserving the parameters of the BIOS when the computer is subdued. Without her, whenever we were lighting we would have to introduce the characteristics of the hard disk, of the chipset, the date and the hour...

It is a question of a battery, since it is recharged when the computer is burning. Nevertheless, with the step of the years there loses little by little this capacity (like all the rechargeable batteries) and comes a moment into which it is necessary to change it. This, that happens between 2 and 6 years after the buy of the computer, can be predicted observing if the hour of the computer "more normal thing is late".

To change it, aim at all the parameters of the BIOS for reescribirlos then, extract the battery (usually of the type of big button or cylindrical like that of the image), take it to an electronics shop and ask for one exactly equally. Or read the manual of the motherboard to see if it has a few connectors to plug in external batteries; if it is like that, note of what model talks each other and buy them.


Varied integrated elements

In the modern basic badges it turns out to be very common that true components are included in the proper motherboard, instead of going in the shape of cards of expansion. The most common are:

  • Devices checkers: in general all the badges Pentium, and some 486, have a few chips in the motherboard who are in charge of handling the hard disks, disk drives and ports series (ports COM); some of high scale even have checkers integrated SCSI.
  • Sound card: now when a card of 16 bits usually consists of the only chip and the connectors, more and more basic badges incorporate it.
  • Video checker: what is called usually "a videocard", but without the card. Those who incorporate the basic badges are not usually of an exceptional potency, but yes sufficient for office works, like for example an Intel 740.

On the expediency or not of that the basic badges have a high grade of integration of components there are opinions for all the tastes. Undoubtedly, they go out cheaper and it is more comfortable, since the interior of the box is clean of cables and cards; nevertheless, not always there are components of high scale (especially in sound cards and video), in addition to which any important mistake in the badge leaves us without almost anything to be able to make use of of the computer.

With this it finishes the description of the elements of the motherboard. If he wants to know the last innovations and tendencies in the modern basic badges, go to the paragraph dedicated to the articles on basic badges that is between the Related Topics.


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