Abstract
This chapter is targeted primarily at someone studying for the A+ Certification exam. You will learn how to identify the built-in components of the motherboard and their functions, the various processors available for use with IBM-compatible PCs, the different types of RAM used in PCs, the different bus architectures used in PCs, and various I/O components and connectors. The chapter ends with a quiz and suggested activities.
Chapter 1 provided an overview of the core components, boot process, operating system, communications between the operating system and core components, and the role applications play in PCs. This chapter provides an in-depth look at the core components.
Upon completion of this chapter, you will be able to
Identify the built-in components of the motherboard and their functions
Identify the various processors available for use with IBM-compatible PCs
Identify the different types of RAM used in PCs
Identify and describe the different bus architectures used in PCs
Identify various I/O components and connectors
CASE/POWER SUPPLY
Cases and Power
Baby tower
20 or fewer inches tall
2 or fewer 5.25-inch bays
1 3.5-inch bay
Mid tower
20 to 30 inches tall
3 5.25-inch bays
1 or more 3.5-inch bays
Full tower
30 inches or taller
4 or more 5.25-inch bays
2 or more 3.5-inch bays
Power supplies from 150 to 500 watts
Three different sizes of cases are available in the tower model:
Baby tower case— Typically 20 or fewer inches high; two 5.25-inch and one or two 3.5-inch drive bays.
Mid-size tower case — Between 20 and 30 inches high; three 5.25-inch and two 3.5-inch drive bays.
Full-size tower case — Typically 30 inches high or taller; four or more 5.25-inch drive bays and at least two 3.5-inch drive bays.
All tower power supplies are at least 150 watts and can go as high as 500 watts. Though most tower power supplies have the same footprint, the wattage, color code on the AC input leads, and power switches can be different.
The area inside the case is known as the air plenum for that case. The case is designed to let cool air enter from the front of the PC through air vents. At that point, a fan located in the power supply unit pulls air across the CPU and memory chips, into the power supply, and out the back of the power supply (see Figure 2.1).
It is important to keep the outer cover and all the slot covers in place on the case for the airflow to properly cool the computer. Cases got larger when components were getting smaller to create a larger air plenum that could better distribute and remove the heat from components.
Important: The case cover and all backplates must be properly installed to maximize proper air flow and heat reduction inside the computer case.
The power supply is responsible for taking Alternating Current (AC) and switching it to Direct Current (DC) voltage for use by the computer. Figure 2.2a shows a variety of power supplies, switches, and fans.
As we said in Chapter 1, the original IBM-compatible PCs were housed in a desktop-style case. The wattage of most power supplies can be found on the top of the power supply, normally displayed on a yellow or white sticker.
The original IBM-compatible PCs had a 63-watt power supply. Newer, high wattage power supplies were created to replace the 63-watt power supply. These newer power supplies have the same footprint and power connectors as their predecessor, so the 150-watt power supplies can be used to replace a 63-watt power supply.
The AT-style power supply has a red thumb-sized power switch located at the right rear of the case (when viewed from the front), but the power supply has a taller footprint than the XT-style case. The AT power supply can be quickly identified by the L-shaped indention to the footprint (Figure 2.2b).
All AT-style cases have the same power supply footprint. With the exception of wattage ratings, the power supplies in the original AT cases are the same. This is also true of the XT cases. All XT power supplies are interchangeable, as long as the replacement power supply has at least as high a wattage rating as the power supply being replaced. This makes power supply replacement a lot simpler.
Newer ATX cases have a different power connector for supplying power to the motherboard. Instead of having two separate power connectors, the ATX power supply has one double-row connector for providing power.
The tower-style cases all have the same power supply footprint, but the length and color of the input leads, number of output connectors, and type of power switch used can vary greatly. For this reason, it is best to visually inspect the power supply being replaced to insure that the replacement power supply will work with that particular case.
On most PC power supplies, the output power leads and connectors are the same. Two connectors (the P8 and P9 connectors) plug into the motherboard and are responsible for providing 5 volts DC and 12 volts DC to the motherboard, processor, and RAM.
When plugging the power connectors into the motherboard, you should orient the ground (black wires) leads toward the center of the connectors, as shown in Figure 2.2c.
Important: The two power connectors that plug into the motherboard should be oriented so that the black wires are toward the center.
Several common connectors for internal components, such as a floppy drive or hard drive, need their own power. These connections provide 5 volts or 12 volts to those devices. The number of connectors will vary, depending on the wattage of the power supply. The common connectors come in a smaller size and a larger size that you can tell apart fairly easily.
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