Because of the tight relationship between BIOS and CMOS, they
are recognized as the same program at most of time, just their name are different. Actually,
they are different two things which are related with each other. So what is
BIOS, CMOS? And what are the difference and relationship between BIOS and CMOS?
One: Concept Difference between BIOS and CMOS
CMOS is Complementary Metal Oxide Semiconductor. Because of its characteristics of the read and write, CMOS is used to save data about computer parameters set in BIOS program on motherboard. So its main function is save data.
BIOS is one EPROM or EEPROM chip on computer motherboard. BIOS Setup program is stored in it, which saves important system information and system parameter.
Actually, BIOS is Basic Input-Output system in microcomputer,
whose content is integrated in a chip on microcomputer motherboard. The most important
input and output program of microcomputer, system information setup, POST and
bootstrap program are saved there.
Two: Main Function Difference between BIOS and CMOS
CMOS main function:
1. Quick Power On Self - Test
When computer is starting, motherboard will take a series check
and test on systems and peripheral devices. If you set it Enabled, computer
startup speed will improve.
2. Boot Up Floppy - Seek
2. Boot Up Floppy - Seek
When computer is starting, BIOS will check whether Floppy is
available. If you choose Enabled, when BIOS find no floppy, it will prompt you
that is wrong.
3. Boot Up NumLock – Status
3. Boot Up NumLock – Status
Generally, the small keyboard in the right side of big
keyboard is used as number keys default. If it is necessary, you can set it
OFF, and small keyboard would become direction keys.
4. Security Option
4. Security Option
There are two options between Security Option, if you set it
as “Setup”, no password is needed to login computer, but password is needed to
enter CMOS, which is set before. And only supervisor password could change parameters
for CMOS. If you set it as “System”, you will need computer logon password, and
only supervisor password could modify CMOS.
How to set password
in CMOS?
Two kinds of password settings are provided in CMOS for
user, Supervisor/User Password). Follow the below:
- Choose Supervisor Password on main interface, press Enter and “Enter Password:” appears.
- The length of password could not be longer than 8 characters. When you finish typing it, press Enter.
- Confirm Password now. Type password you just input and press Enter to make sure.
Tips: When you set
Security Option as “System”, you can type one of Supervisor password or User
password to access Windows computer. And please remember back to main interface
and press F10 and Enter to save these changes.
BIOS main function
1. BIOS Interrupt Service Program
It is a programmable interface between software and hardware
in microcomputer system. It makes application software functions appropriate link
up to microcomputer hardware. The management on floppy, disk, CD-ROM, keyboard,
displayer is based on BIOS system interrupt service program. And computer
operator could call this program directly by accessing break point, such as INT5
and INT13 etc.
2. BIOS System Setup Program
This program is used to set parameters for CMOSRAM. Just
press boot key when you start computer and you will enter this program. And this
process to set parameters for CMOS is also called BIOS settings.
3. Electricity Self-Inspection Programs on the POST
When microcomputer is connected with power, POST will check equipment
inside system. Once there is problem in check process, system prompt message
will pops up for computer user.
4. BIOS System Bootstrap Program
After system POST completes, ROMBIOS will search for soft
and hard disk drive, CD-ROM, Network Server according to setup sequence saved
in CMOS settings. Read operational system boot record and give control
privilege to boot record. Boot record will let system boot successfully.
Relationship between BIOS and CMOS
From the above introduction, you can see BIOS and CMOS is
inseparable. We have to set up CMOS through BIOS setup program, and BIOS
information is stored in CMOS. So at most of time, we usually called CMOS
setting as BIOS setting. Both of them are settings on computer hard ware. And
setting parameters are saved in CMOS chip.
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