1. Prepared By
Samira Dayan Jayasekara

2. 1. Startup BIOS runs power-on self test (POST)
and assigns resources
2. ROM BIOS startup program searches for and
loads an OS
3. OS configures the system and completes its
own loading
4. Application software is loaded and executed

5.  BIOS executes MBR program
◦ Turns to partition table to find OS boot record
 Program in OS boot record attempts to
find a boot loader program for OS
◦ Ntldr (Windows NT/2000/XP)
◦ Io.sys (Windows 9x)

8.  Bridges connect the devices
◦ But without a program, they don’t know how to
communicate
 A special kind of program is required to enable
the CPU to talk to other devices(that teaches the
CPU about a particular device)
 Perfect place to store the support
programming is on the motherboard
◦ On a special type of device called a read-only memory
(ROM) chip
◦ Modern(A Flash ROM chip stores these programs)
 These programs are collectively known as the
basic input/output service (BIOS)

9.  ROM chip stores programs exactly like RAM
 Differs from RAM in two important ways
◦ ROM chips are non-volatile
 Meaning that the information stored on ROM isn’t erased
when the computer is turned off
◦ Second, traditional ROM chips are read-only,
 Meaning that once a program is stored on one, it can’t be
changed
 Modern motherboards use a type of ROM called
◦ Flash ROM that differs from traditional ROM in that you
can update and change the contents through a very
specific process called ―flashing the ROM

10.  Each program is called a service
 Programs stored on Flash ROM chips are known
as firmware
◦ as opposed to program stored on erasable media that are
collectively called software
Keyboard
controller
chip

11.  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

12.  Separate chip from ROM BIOS
◦ Separate memory chip, called the complementary
metal-oxide semiconductor (CMOS) chip
 Volatile (kept alive by battery)
 Stores only changeable data
◦ Not programs
◦ Acts as clock to keep data current
◦ information that describes specific device
parameters
 Customizable via SETUP program
 Often on Southbridge

13.  CMOS
 BIOS
◦ Data
◦ Programs
◦ Non-volatile (stays same ◦ Volatile (kept alive with
after power off) battery)
◦ Can be changed by ◦ Changed via CMOS setup
―flashing‖
◦ Typically 128 K of data
◦ Typically 64 K of (though chip size is
programs (though Flash
typically 64 K)
ROM is much bigger)
◦ Often a separate chip ◦ Often on Southbridge

14. 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)

15. • Main menu
– Access to all submenus

16. • Clock, hard drives, floppy drives

17.  Normally set to Default or Auto for all

18.  POST, boot order

19.  Use to enable/disable power-saving features

20.  Rarely need to manipulate on today’s PCs

21.  Locks access to CMOS settings
◦ Prevents non-techs from changing key settings

22.  If your system keeps resetting
◦ Replace the battery
 Common symptoms of low battery
◦ Slow running clock
◦ Clock resetting to January 1st

23.  To clear the CMOS settings, place the shunt
on the CMOS jumper
◦ Resets to factory settings
◦ Resets password

24. IT Technician
CompTIA A+
Technician

25.  The power-on self test (POST) is a special
program stored on the ROM chip
◦ Initiated when the computer is turned on or is reset
◦ Checks out the system every time the computer
boots

26.  To perform this check, the POST
◦ Sends out a standard command that says to all the devices,
―Check yourselves out!‖
◦ All the standard devices in the computer then run their own
internal diagnostic
◦ The POST doesn’t specify what they must check.
◦ The quality of the diagnostic is up to the people who made
that particular device.
 Device — keyboard controller chip runs its
diagnostic and determines that it is not working
properly
 Communicates errors
◦ Beep codes
◦ Text errors

27.  A series of beeps—called beep codes—if
anything went wrong
◦ For bad or missing video :
 One long beep followed by three short beeps
 End of a successful POST, the PC will produce
one or two short beeps, simply to inform you
that all is well

28.  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 found in
legacy computers
◦ Check motherboard manual for meaning

29.  Any POST errors will display on the screen as
a text error
 Text error, the problem is usually, but not
always, self-explanatory
 Far more useful than beep errors because you
can simply read the screen to determine the
bad device

31.  POST cards are devices that monitor POSTs and
report on the hardware that may be causing
problems
◦ Turn the PC off, plug in the card,
and reboot
◦ POST error codes do not fix the
computer – they just tell you
where to look
◦ If all else fails, replace the
motherboard

32.  POST cards are simple cards that snap into
an expansion slot on your system. A small,
two-character light-emitting diode (LED)
readout on the card indicates what device
the POST is currently testing
 PC to act dead—no beeps and nothing on
the screen
◦ POST card, to monitor the POST and identify which
piece of hardware is causing the trouble