PC Hardware A Beginner’s Guide

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Chapter 15: The System Case^349


Power Button


On older PCs, the power switch was a part of the power supply and extended through
the case wall on the right rear corner of the PC. Nowadays, the power switch is located
on the front panel.
On Baby AT and earlier systems, the power switch located on the front panel is not a
switch in the sense of a physical on/off switch. It is actually a proxy switch; pressing the
front-panel switch activates the actual power supply switch, which is located on the back
of the front panel and wired directly to the power supply.
Newer systems such as the ATX, NLX, and LPX form factors have an actual power
switch on the front panel, but instead of being wired to the power supply, the switch is
now electronic and connected to the motherboard. On these systems, you don’t turn the
computeronoroffwiththepowerswitch;yourequestthatthemotherboarddoitforyou.


Reset Button


Thereset switch, also referred to as thereset button, performs a hardware reset when
pressed. This provides the user with a means of restarting the PC should it halt and not
respond to normal shutdown or restart commands. Using the reset button is better than
powering the PC off and back on, which can sometimes result in POST or BIOS errors.
On some older PCs, the reset button was placed on the front panel and easily ac-
cessed, which caused more than one unexpected system reset. Newer cases now recess
the reset switch to prevent inadvertent resets from taking place. A few manufacturers
have moved the reset button to the back of the PC, which is safer yet.
Somemanufacturers,suchasGateway,donotincludearesetbuttonontheirsystems.
Resetting the PC must be done via the keyboard (CTRL-ALT-DEL) or using the operating
system’s restart process.


Turbo Button


As explained earlier (see “Status LEDs” earlier in this section), the turbo button and its
functions are now obsolete except on 286 and early 386 computers. If your front panel has
a turbo button, chances are it is not connected to anything; to avoid possible problems,
you should never press it.


Keylocks


Although not technically a switch, some cases have keylocks on their front panels. There
are two types of keylocks available on PC front panels:


 Keyboard lockout When locked, this type of keylock locks out the keyboard
for the system, preventing anyone from using the PC. When someone attempts
to use the PC while this keylock is locked, an error message is displayed on the
monitor that says, in effect, that the system is not available for use. While this
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