7/31/2019 PP_ch05f
1/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
BIOS and CMOSChapter 5
7/31/2019 PP_ch05f
2/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Overview
In this chapter, you will learn to
Explain the function of BIOS
Distinguish among various CMOS setup utilityoptions
Describe option ROM and device drivers
Troubleshoot the power-on self test (POST)
7/31/2019 PP_ch05f
3/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
We Need to Talk
Historical/Conceptual
7/31/2019 PP_ch05f
4/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Bridge Introduction
Data flows through the computer Between CPU and RAM
Between CPU and video
Between CPU and other devices
Bridges are used to connect the pieces
Northbridge
Bridge closest to the CPU
Southbridge The farther bridge
7/31/2019 PP_ch05f
5/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Northbridge & Southbridge
Northbridge
Chip or chips thatconnect the CPU tovideo and/or memory
Southbridge
Handles all of the inputsand outputs to themany devices in the PC
A chipset is a set of Northbridge andSouthbridge chips that work together
Explored in more depth in Chapter 7
7/31/2019 PP_ch05f
6/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Data Flow
Northbridge and Southbridgehave connectivity with all devices
Not the same in all systems
7/31/2019 PP_ch05f
7/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Chipset
Northbridge
Southbridge
7/31/2019 PP_ch05f
8/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Basic Input/Output System(BIOS)
Bridges connect the devices But without a program, they dont know how
to communicate
A special kind of program is required toenable the CPU to talk to other devices
A Flash ROM chip stores theseprograms
These programs are collectively knownas the basic input/output service(BIOS)
7/31/2019 PP_ch05f
9/38
7/31/2019 PP_ch05f
10/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
BIOS
Each program is called a service Programs stored on Flash ROM chips are
known as firmware
Programs stored on erasable media are
called software Keyboardcontroller
chip
7/31/2019 PP_ch05f
11/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
CMOS
Essentials
CompTIA A+Essentials
7/31/2019 PP_ch05f
12/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
CMOS
Separate chip from ROM BIOS
Volatile (kept alive by battery)
Stores only changeable data Not programs
Acts as clock to keep data current
Customizable via SETUP program
Often on Southbridge
7/31/2019 PP_ch05f
13/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
BIOS vs. CMOS
BIOS Programs
Non-volatile (stayssame after power off)
Can be changed byflashing
Typically 64 K ofprograms (though FlashROM is much bigger)
Often a separate chip
CMOS Data
Volatile (kept alive withbattery)
Changed via CMOSsetup
Typically 128 K of data(though chip size istypically 64 K)
Often on Southbridge
7/31/2019 PP_ch05f
14/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Updating CMOS
Updated via BIOS program Three primary BIOS brands
American Megatrends (AMI), Award, Phoenix
To enter setup, press key combination
(may be Del, ESC,F1, F2,CTRL-ALT-ESC,CTRL-ALT-INS,CTRL-ALT-Enter,
or CTRL-S)
7/31/2019 PP_ch05f
15/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
CMOS Setup
Main menu Access to all submenus
7/31/2019 PP_ch05f
16/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Standard CMOS Features
Clock, hard drives, floppy drives
7/31/2019 PP_ch05f
17/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
SoftMenu Setup
Normally set to Default or Auto for all
7/31/2019 PP_ch05f
18/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Advanced Features
POST, boot order
7/31/2019 PP_ch05f
19/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Power Management
Use to enable/disable power-savingfeatures
7/31/2019 PP_ch05f
20/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
PnP/PCI
Rarely need to manipulate on todays PCs
7/31/2019 PP_ch05f
21/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Set Password
Locks access to CMOS settings Prevents non-techs from changing key settings
7/31/2019 PP_ch05f
22/38 2007 The McGraw-Hill Companies, Inc. All rights reserved
Option ROM and Device Drivers
7/31/2019 PP_ch05f
23/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
BYOB
Computer makers could not predict allthe new types of hardware
Ways to bring your own BIOS (BYOB)were invented:
Option ROM is a BIOS chip embedded on theadapter card itself (i.e., video cards)
Most new hardware devices use device drivers
to tell the BIOS how to talk to the CPU
Most devices with onboard BIOS use it only forinternal needs (internal function) and use adevice driver to talk to the CPU
7/31/2019 PP_ch05f
24/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Device Drivers
A device driver is a file that contains theBIOS commands necessary tocommunicate with the devices theysupport
Loaded into RAM when the system boots
All devices come with their own devicedrivers
7/31/2019 PP_ch05f
25/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
BIOS, BIOS, Everywhere
All hardware needs a program to allowCPU to communicate with it
Could be on motherboard ROM
Could be on PC card ROM
Could be loaded via a driver
Could be loaded into RAM at boot
7/31/2019 PP_ch05f
26/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Power-On Self Test (POST)
CompTIA A+Technician
IT Technician
7/31/2019 PP_ch05f
27/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Power-On Self Test (POST)
The power-on self test (POST) is aspecial program stored on the ROM chip
Initiated when the computer is turned on or isreset
Checks out the system every time the computerboots
Communicates errors
Beep codes
Text errors
7/31/2019 PP_ch05f
28/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Beep Codes
If video is determined to be missing or faulty One long beep followed by three short beeps
If everything checks out
One or two short beeps
If RAM is missing or faulty
Buzzing noise that repeats until power turned off
More complicated beep codes may be foundin legacy computers
Check motherboard manual for meaning
7/31/2019 PP_ch05f
29/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Text-Based Error Message
7/31/2019 PP_ch05f
30/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
POST Cards
POST cards are devices that monitor POSTsand report on the hardware that may becausing problems
Turn the PC off, plug in the card,and reboot
POST error codes do not fix thecomputer they just tell you
where to look
If all else fails, replace themotherboard
7/31/2019 PP_ch05f
31/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
The Boot Process
The CPU is the first component initializedwhen the computer is turned on
It reads a special wire called power good
once the power supply provides theproper voltage to the CPU
Every CPU has a built-in memory addresswith the first line of the POST programon the system ROM
7/31/2019 PP_ch05f
32/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
The Boot Process
The last BIOS function called by POST isthe bootstrap loader
The bootstrap loader loads the operating
system from the boot sector Searches the floppy, CD-ROM, or the hard drive
Boot order set in CMOS
The bootstrap loader generates an errorif it cannot find the boot sector on thebootable disk
7/31/2019 PP_ch05f
33/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Care and Feeding of CMOS/BIOS
We have met the enemy and he is us.- Pogo
7/31/2019 PP_ch05f
34/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Losing CMOS Settings
Common errors CMOS configuration mismatch
CMOS date/time not set
No boot device available
CMOS battery state low
Common reasons for losing CMOS data
Jiggling the battery while doing other work
Dirt on the motherboard Electrical surges
Faulty power supplies
Chip creep
7/31/2019 PP_ch05f
35/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Losing CMOS Settings
If your system keeps resetting
Replace the battery
Common symptoms of low battery
Slow running clock
Clock resetting to January 1st
7/31/2019 PP_ch05f
36/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Clearing CMOS Settings
To clear the CMOS settings, place theshunt on the CMOS jumper
Resets to factory settings
Resets password
7/31/2019 PP_ch05f
37/38
2007 The McGraw-Hill Companies, Inc. All rights reserved
Flashing ROM
Flash ROM chips can be reprogrammed
Download program from manufacturer
Copy program to floppy
Some programs will run within Windows
Boot to floppy and run program
7/31/2019 PP_ch05f
38/38
Recommended