Comptia A+ Capitulo 3

Foundation Topics: Motherboards and Their Components
The motherboard represents the logical foundation of the computer. In other words, everything that makes a computer a computer must be attached to the motherboard. From the CPU to storage devices, from RAM to printer ports, the motherboard provides the connections that help them work together. Figure 3-1 shows an example of a typicalmotherboard. The various components of the motherboard are called out in the figure. We will be referring to this figure throughout the chapter.

Figure 3-1. A typical motherboard.

The motherboard is essential to computer operation in large part because of the two major buses it contains: the system bus and the I/O bus. Together, these buses carry all the information between the different parts of thecomputer. The location and orientation of these busses will vary depending on the type of form factor used. The form factor is the design of the motherboard, which the case and power supply must comply with. Motherboards can come with integrated I/O ports; these are usually found as a rear port cluster. The motherboard will also have memory slots, which allow a user to add sticks of RAM, thusincreasing the computer’s total resources. Of course, the motherboard also has expansion slots most commonly used by audio and video cards, although the slots can be used by many other types of cards as well. You will also find mass storage ports for hard drives, CD-ROMs, and DVD-ROMs on the motherboard. After we cover all of these concepts, we’ll show how to select, install, and troubleshoot themotherboard. As you can see, the motherboard is the central meeting point of all technologies in the computer. There is a lot to cover concerning motherboards. Let’s begin by discussing the system and I/O busses.
The System Bus and I/O Bus
The system bus carries four different types of signals throughout the computer:
* Data
* Power
* Control
* Address
To help you understand thisconcept, let’s take an imaginary trip to Chicago and compare the city to a typical motherboard. If you were on the Willis Tower observation deck overlooking downtown Chicago one evening, you would first notice the endless stream of cars, trucks, and trains carrying people and goods from everywhere to everywhere else along well-defined surface routes (the expressways and tollways, commuterrailroads, Amtrak, and airports). You can compare these routes to the data bus portion of the system bus, which carries information between RAM and the CPU. If you’ve ever listened to the traffic reports on a radio station such as Chicago’s WBBM (780 AM), you’ve heard how traffic slows down when expressway lanes are blocked by construction or stalled traffic. In your computer, wider data buses that enablemore “lanes” of data to flow at the same time promote faster system performance.
Now, imagine that you’ve descended to street level, and you’ve met with a local utility worker for a tour of underground Chicago. On your tour, you will find an elaborate network of electric and gas lines beneath the street carrying the energy needed to power the city. You can compare these to the power lines in thesystem bus, which transfer power from the motherboard’s connection to the power supply to theintegrated circuits (ICs or chips) and expansion boards connected to the motherboard.
Go back to street level, and notice the traffic lights used both on city streets and on the entrance ramps to busy expressways, such as the Eisenhower and the Dan Ryan. Traffic stops and starts in response to thesignals. Look at the elevated trains or at the Metra commuter trains and Amtrak intercity trains; they also move as directed by signal lights. These signals, which control the movement of road and rail traffic, can be compared to the control lines in the system bus, which control the transmission and movement of information between devices connected to the motherboard.
Finally, as you look around...