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Chapter 4 BIOS Setup Utility
BIOS stands for Basic Input and Output System. It was once called ROM BIOS when it was
stored in a Read-Only Memory (ROM) chip. Now manufacturers would like to store BIOS in
EEPROM which means Electrically Erasable Programmable Memory. BIOS used in this series
of mainboard is stored in EEPROM, and is the first program to run when you turn on your
BIOS performs the following functions:
1. Initializing and testing hardware in your computer (a process called "POST", for Power On
2. Loading and running your operating system.
3. Helping your operating system and application programs manage your PC hardware by
means of a set of routines called BIOS Run-Time Service.
4.1 About BIOS Setup
BIOS Setup is an interactive BIOS program that you need to run when:
1. Changing the hardware of your system. (For example: installing a new Hard Disk etc.)
2. Modifying the behavior of your computer. (For example: changing the system time or date,
or turning special features on or off etc.)
3. Enhancing your computer's behavior. (For example: speeding up performance by turning
on shadowing or cache)
4.2 To Run BIOS Setup
First access BIOS setup menu by pressing <F1> key after “POST” is complete (before OS is
loaded). After the ﬁrst BIOS be setupped(or loaded default values) and save, the <DEL> key
will be pressed if you will enter BIOS setup menu.
4.3 About CMOS
CMOS is the memory maintained by a battery. CMOS is used to store the BIOS settings you
have selected in BIOS Setup. CMOS also maintains the internal clock. Every time you turn
on your computer, the BIOS Looks into CMOS for the settings you have selected and
conﬁgures your computer accordingly. If the battery runs out of power, the CMOS data will
be lost and POST will issue a “CMOS invalid” or “CMOS checksum invalid” message. If this
happens, you have to replace the battery and check and conﬁgure the BIOS Setup for the
4.4 The POST (Power On Self Test)
POST is an acronym for Power On Self Test. This program will test all things the BIOS does
before the operating system is started. Each of POST routines is assigned a POST code, a
unique number which is sent to I/O port 080h before the routine is executed.