The System Unit - Computing Fundamentals - page 33

Step by Step

Exploring Your Motherboard
Use this procedure to see what components and connectors your motherboard has. Use a desktop computer for this
exercise.

1 Shut down the computer, and open up the system unit. You may need a Phillips screwdriver. Ask your instructor for
assistance if needed. Do not touch anything inside the system unit

2 Locate the following components. Ask your instructor to confirm that you are correct:

◾ CPU (may be under a heat sink)

◾ System memory

◾ Built-in USB ports

◾ Other built-in ports (name them if you can)

◾ Expansion slots (identify the type if you can)

3 Trace each cable from the motherboard to the components to see how components such as the hard drive and
power supply attach to the motherboard.

4 Close the system unit's case and replace any screws you removed.

Quick Review
1 If you see a DVI port built into a motherboard, what type of capability can you assume is built into the motherboard?

2 What is PCI Express (PCIe)?

Understanding Power Supplies
The power from your wall outlet is alternating current (AC), and is
either 110 volt (v) or 220v, depending on the country in which you live.
Computer components require direct current (DC) and require much
lower voltages. A power supply has two jobs:

power supply A component that converts
AC power from a wall outlet to DC power and
decreases the voltage to the level needed for the
computer to operate.

◾

It converts AC to DC power.

◾ It decreases the voltage to the amount required for each
component.

In a desktop PC, a power supply is a large silver metal box mounted in
one corner of the system unit, with many bundles of colored wires and
connectors emerging from it (see Figure 2.7). The wire colors are signifi-
cant; each wire color carries a different voltage. Each connector has the
appropriate wires running to it to deliver the exact voltage required for
each connected device. The most common wire colors are red, yellow,
and black. The connector shown in Figure 2.8, for example, uses one red
wire, one yellow wire, and two black wires. The power comes in on the
red and yellow wires, and the black wires are for grounding.

A desktop PC's power supply has a fan in it, and when you start up the
PC, the fan starts up too. The fan pulls hot air out of the power sup-
ply, and has a side benefit of circulating air through the entire system
unit too.