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Does your PC really turn off when you shut down and close the office door? How does your PC
remember all the settings it needs in order to load that
wonderful operating system bundled with your newly purchased Christmas toy?
As you go to power on your new PC to surf the
Internet financial pages you notice that several
unexplainable messages appear on your screen before
the Windows desktop becomes active and available.
All manner of system items such as memory, disk
drive details, and integrated device settings pass
before your eyes. Where did all that come from? You
seem to remember something in your computer class
about everything being lost when the power turns off?
Well, sort of.
Let's cover some ground here and discuss the
intricate details of what really goes on under the hood
of your PC when you power it up. A successful boot
sequence depends on data stored on a special type
of memory chip that's attached to the main circuit board in your PC. Although it isn't particularly
important to know where this chip resides, it is
important to know that it exists. This little chip is
often referred to as the CMOS, which stands for
Complementary Metal Oxide Semiconductor. The CMOS chip is like the alarm clock in your bedroom that
always remembers the time even when the power goes out. Like your alarm clock, the CMOS chip has
a small on-board battery that provides power, so it
can retain all the information necessary to start the
PC properly. If something goes wrong with the
battery, the CMOS loses all these settings, which causes
your computer to effectively "lose its mind."
Older PCs such as the IBM XT and AT computers used DIP switches on the main board to set
information about the hardware. If a floppy drive or
memory was added to the system, you had to take off
the cover and manually configure the DIP switch
settings according to the device instructions. Most
novice computer users found this a daunting task.
Fortunately, IBM developed the CMOS chip to store hardware information, so you wouldn't have to
tinker with DIP switches anymore. CMOS is a kind of
random access memory (RAM). Random access memory is
volatile memory, which means it does not remain stored if the power is turned off.
However, the CMOS requires very little power. That small
on-board battery is all it needs to maintain the
hardware settings for your PC for years even though the
power to the PC itself is off.
CMOS chips pass information to the BIOS (Basic Input/Output System) when the computer is
turned on (called bootup). CMOS stores information such
as boot order (the order the computer looks for
information, such as A drive first, C drive second, and
so on), real-time system clock, calendar settings,
hardware passwords, hard drive configuration
settings, and the installed memory (RAM). Essentially
the CMOS chip stores data for the BIOS so that a
computer can boot up properly.
Now that you know about the CMOS chip and how it stores BIOS information, you may be
wondering how you can get at this information. The
answer to this question depends on the age of the
computer. Assuming you purchased your home PC in the
last four years, you access the CMOS settings by
pressing a key such as F10 or the Delete key while the
computer is booting up. A message on your screen
may say something like "Press F10 to access setup,"
for example. If you don't see this message during
boot up check your PC owner's manual. After you
press the key, you enter the CMOS/BIOS editing
utility. The first thing you notice is that the pretty
graphical interface you usually see is gone. Don't worry.
This character-based screen is a natural part of the
CMOS editor. To move around inside the utility
program, you use the tab and arrow keys on your keyboard.
A mouse doesn't operate in this utility.
The CMOS editor is typically composed of five major sections that are accessed using menus.
These screens vary depending on PC manufacturer, PC
age, and the BIOS manufacturer. However, they are
often organized as follows:
- Standard CMOS Setup: In this menu, you can
set system time, date, hard disk drive type, video
settings (such as EGA, VGA, and so on). This menu may also be referred to as MAIN depending
on your BIOS, computer age, and manufacturer.
- BIOS Features Setup: This menu lets you
change system settings such as boot sequence,
character typing input rates, CPU cache settings,
security options, and virus warning settings. This
menu may also be called ADVANCED depending on your BIOS.
- Security: This menu lets you change the
passwords used to access the BIOS. This menu is
particularly useful for changing settings for multi user
workstations where you don't want wandering curious
fingers running amok.
- Power Management: You change power saver
settings in this menu. These settings may be
particularly important if the PC is a laptop and
battery consumption is an issue.
- Boot Options: On some CMOS editors this is
a separate item from the BIOS features setup.
The CMOS is the heart of the PC and before you delve into it, you should make a note of the
current CMOS settings. Incorrect CMOS values can
easily render a PC inoperable. Hit the Print Screen
key prior to changing CMOS settings to make a record
of the existing settings. Or write down the settings on
a piece of paper for future reference. If all else fails
and you can't find your initial values, your CMOS
editor should allow you to load system defaults as a way
of getting you back to the correct configuration.
Editing the CMOS affects the functioning of the BIOS. Your PC uses the BIOS to properly load
the operating system upon powering on the
computer. Editing the CMOS settings is a particularly good
way to learn about the inner workings of your PC.
Don't be afraid to carefully investigate these settings
and how they are used to operate your PC.
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