BIOS stands for Basic
Input Output System. The BIOS is the software that
starts when you turn on your computer, and it provides a number of
functions designed to get your computer up and running. As you can guess,
if your BIOS isn't configured correctly, your computer won't start
correctly. The BIOS must do its job before your computer can load its
operating system and applications.
In this week's
feature, I'll take a look at the BIOS: what it is and what it does. In a
future article, I'll talk about how you can change BIOS settings, and what
can go wrong. This discussion is specifically aimed at PC compatible
computers; Macintosh computers also have a BIOS, but it is very different
from the PC. Also keep in mind that you shouldn't change the settings in
your BIOS unless you are confident that you can reverse the changes. If
you make a mistake in your BIOS settings, your computer may be inoperable
until you correct the error.
The BIOS: What It Is, What It Does
The Basic
Input/Output System is the software that comes before all other software.
Unlike your operating system or applications, the BIOS is stored on a chip
which is mounted on your computer's motherboard.
When the computer is first powered on, the BIOS starts immediately and
begins a number of critical tasks. For most computer systems, these tasks
include:
- identifying and initializing the computer's video
card or integrated graphics,
- setting the computer's clock
- identifying the computer's RAM
memory, and performing a quick test to make sure the memory is
responding,
- locating and identifying the computer's hard
disk(s) and other storage devices,
- initializing the computer's standard input/output ports
(specifically, the serial
and parallel
ports, and possibly the USB
ports)
- juggling various system
resources so that all the PCI
and ISA
cards in the system can work together
- passing control of the computer to the operating system stored on
the hard disk
The various BIOS
settings are stored in a special type of memory called CMOS,
which requires a small constant electric current to function. So,
motherboards have a battery (usually called the "CMOS battery")
which powers the system clock when the computer is turned off, and keeps
the CMOS memory active. If you look at your motherboard, you'll probably
see a disk-shaped or cylindrical battery mounted in a socket. If the
battery goes dead, your BIOS will forget all its important settings, like
the current date & time.
The BIOS chip
itself is also specially designed. Most BIOS chips are mounted in a
socket, in case they become damaged and emergency replacement is required
to bring the computer back up. The BIOS chips are also erasable and
rewritable; updating the chip with new BIOS software is called
"flashing the BIOS", a reference to the old method of shining
ultraviolet light on programmable chips to erase them. Flashing the BIOS
is a delicate operation, because a power outage during the flash process
can leave the BIOS partially written and the computer unusable.
Fortunately, many new computers have special recovery mechanisms, like the
Dual
BIOS feature on Gigabyte
motherboards, or the AZZA
Key Bios device.
Because the BIOS
is hidden from everyday examination, it can be hard to identify your BIOS
or determine what features and capabilities it supports. Fortunately,
there are convenient utilities which can report lots of useful information
about your BIOS. One of them is the BIOS
Wizard, from biosupgrades.com.
