a functioning computer with the push of the On button? Put another way,
how does a laptop know how to load and act on instructions before it’s
already at work?
The answer lies in the interaction between something called the basic input/
output systemor BIOS,the lowest-level set of instructions for your computer
and an equivalent set of basic code put in place on the hard disk drive when
the system first received power. The process is called bootingthe computer,
as in the old (and physically impossible) assignment of “pulling yourself up
by your bootstraps.”
The BIOS in a modern laptop is a single chip that establishes your machine’s
basic personality; a whole industry of companies writes this sort of code, selling
it to laptop makers. Thus, a modern Toshiba may use a BIOS made by Phoenix;
Dell and IBM have offered machines with BIOS code written in-house as well as
by a third party. (Phoenix and Award merged in 1998; the other big player in the
field is American Megatrends, Inc. or AMI. Smaller companies, often supplying
generic BIOS code to generic laptop makers, include ABIT and MR BIOS.)
As a laptop owner, here’s what you need to know about BIOS code:
Every machine has to have one.
Some are slightly better than others.It is somewhere between extremely difficult and impossible to change
one brand of BIOS to another in a machine you already own.
A modern BIOS rarely fails, although electrostatic shock or virus could
result in damage or changes to its code.BIOS chips in current laptop models use a technology called Electrically
Erasable Programmable Read-Only Memory (E-PROM). If you stop and
think about it, this is somewhat contradictory title: a chip that’s both
read-only (meaning it cannot be written to) and electrically erasable and
programmable (meaning its contents can be expunged and replaced
with new information). What this really means is that the user or a repair
facility can restore the BIOS programming or update it to a newly defined
version of the BIOS.The BIOS serves three functions: bootstrapping the system to life; conducting
a quick diagnostic check of the motherboard, memory, and input/output
devices and ports; and then overseeing the most basic system functions that
operate outside the operating system. The BIOS, for example, is in charge of
managing the incoming signals from the keyboard and the in-and-out pulses
from the mouse or other pointing device.
In both logical and physical terms, the BIOS sits between the hardware on
and attached to the motherboard and the operating system, which is first
resident on the hard drive and later is loaded into memory. Many advanced
motherboard and adapters features — in a laptop this includes devices
Chapter 6: Brain Matters: Memory, Microprocessors, and BIOS 101