CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [34]
Figure 3-31 eSATA jack
Inside the System Unit
Now that you’ve seen the devices that connect to the PC, it’s time to open up the system unit to inspect the major internal components of a typical PC. A single PC is composed of thousands of discrete components. Although no one can name every tiny bit of electronics in a PC, a good technician should be able to name the major internal components that make up the typical PC. Let’s open and inspect a system unit to see these components and gain at least a concept of what they do. In later chapters, you’ll see all of these components in much more detail.
Case
The system unit’s case is both the internal framework of the PC and the external skin that protects the internal components from the environment. Cases come in an amazing variety of styles, sizes, and colors. Figure 3-32 shows the front and back of a typical PC case. The front of the case holds the buttons for turning the system on and off, lights to tell you the status of the system, and doors for accessing removable media drives such as floppy, CD-ROM, and DVD drives. This system also provides USB, FireWire, and audio connections in the front for easy access if you want to use a device that needs these connections.
The back of the case holds the vast majority of the system unit connections. You will also notice the power supply—almost always at the top of the case—distinguished by its cooling fan and power plug. Note that one area of the back, the I/O area, holds all of the onboard connections (see Figure 3-33), while another area in the back contains slots for cards. Similarly, the case uses slots to enable access to the external connectors on cards installed in the system unit.
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NOTE You’ll hear the PC case called the enclosure, especially at the more expensive end of the spectrum. Case, enclosure, and system unit are interchangeable terms.
Figure 3-32 Case—front and back
Opening a case is always…interesting. There’s no standard way to open a case, and I’m convinced that the folks making system units enjoy some sick humor inventing new and complex ways to open them. In general, you detach the sides of a case by removing a few screws in the back of the system unit, as shown in Figure 3-34. Use common sense and you won’t have too many problems. Just don’t lose track of your screws or where each one was inserted!
Once you’ve opened the case, take a look inside. You’ll see metal framework, all kinds of cables, and a number of devices. As you inspect the devices, you may gently push cables to the side to get a better view. Don’t forget to wear an anti-static wrist strap (attaching it to any handy metal part of the case) or touch the metal case occasionally to prevent ESD.
Figure 3-33 Onboard devices
Figure 3-34 Opening a system unit
CPU
The central processing unit (CPU), also called the microprocessor, performs all of the calculations that take place inside a PC. CPUs come in a variety of shapes and sizes, as shown in Figure 3-35.
Modern CPUs generate a lot of heat and thus require a cooling fan and heat sink assembly to avoid overheating (see Figure 3-36). A heat sink is a big slab of copper or aluminum that helps draw heat away from the processor. The fan then blows the heat out into the case. You can usually remove this cooling device if you need to replace it, although some CPU manufacturers have sold CPUs with a fan permanently attached.
CPUs have a make and model, just like automobiles do. When talking about a particular car, for example, most people speak in terms of a Ford Taurus or a Toyota Camry. When they talk about CPUs, people say Intel Core i7 or AMD Phenom. Over the years, there have been only a few major CPU manufacturers, just as there are only a few major auto manufacturers. The two most common makes of CPUs used in PCs are AMD and Intel.
Figure 3-35 Typical CPUs still in protective packaging