One of the most common uses of
Flash memory is for the
basic input/output system
of your computer, commonly known as the BIOS (pronounced "bye-ose"). On
virtually every computer available, the BIOS makes sure all the other
chips, hard drives, ports and CPU function together.
Every
desktop and
laptop computer in common use today contains a
microprocessor as its central processing unit. The microprocessor is the
hardware component. To get its work done, the microprocessor executes a set of instructions known as
software (see
How Microprocessors Work for details). You are probably very familiar with two different types of software:
The BIOS software has a number of different roles, but its most
important role is to load the operating system. When you turn on your
computer and the microprocessor tries to execute its first instruction,
it has to get that instruction from somewhere. It cannot get it from the
operating system because the operating system is located on a hard
disk, and the microprocessor cannot get to it without some instructions
that tell it how. The BIOS provides those
instructions. Some of the other common tasks that the BIOS performs include:
- A power-on self-test (POST) for all of the different
hardware components in the system to make sure everything is working
properly
- Activating other BIOS chips on different cards installed in the computer - For example, SCSI and graphics cards often have their own BIOS chips.
- Providing
a set of low-level routines that the operating system uses to interface
to different hardware devices - It is these routines that give the BIOS
its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting.
- Managing a collection of settings for the hard disks, clock, etc.
- Whenever you turn on your computer, the first thing you see is the
BIOS software doing its thing. On many machines, the BIOS displays text
describing things like the amount of memory installed in your computer,
the type of hard disk and so on. It turns out that, during this boot
sequence, the BIOS is doing a remarkable amount of work to get your
computer ready to run. This section briefly describes some of those
activities for a typical PC.
-
After checking the CMOS Setup and loading the interrupt handlers,
the BIOS determines whether the video card is operational. Most video
cards have a miniature BIOS of their own that initializes the memory and
graphics processor on the card. If they do not, there is usually video
driver information on another ROM on the motherboard that the BIOS can
load.
In the previous list, you saw that the BIOS checks the CMOS Setup for
custom settings. Here's what you do to change those settings.
To enter the CMOS Setup, you must press a certain key or combination of keys during the initial startup sequence.
Most systems use "Esc," "Del," "F1," "F2," "Ctrl-Esc" or "Ctrl-Alt-Esc"
to enter setup. There is usually a line of text at the bottom of the
display that tells you "Press ___ to Enter Setup."
Occasionally, a computer will need to have its BIOS updated. This
is especially true of older machines. As new devices and standards
arise, the BIOS needs to change in order to understand the new hardware.
Since the BIOS is stored in some form of ROM, changing it is a bit
harder than upgrading most other types of software.
To change the BIOS itself, you'll probably need a special program
from the computer or BIOS manufacturer. Look at the BIOS revision and
date information displayed on system startup or check with your computer
manufacturer to find out what type of BIOS you have. Then go to the
BIOS manufacturer's Web site to see if an upgrade is available. Download
the upgrade and the utility program needed to install it. Sometimes the
utility and update are combined in a single file to download. Copy the
program, along with the BIOS update, onto a floppy disk. Restart your
computer with the floppy disk in the drive, and the program erases the
old BIOS and writes the new one. You can find a BIOS Wizard that will
check your BIOS at BIOS Upgrades.