1. Basic Input/Output System
Unit objectives
Access the BIOS setup utility and modify hardware configuration values
Explain the POST and boot processes
Install a BIOS update
Troubleshoot BIOS and POST-related problems

2. Topic A Topic A: BIOS and CMOS Topic B: The POST process
Topic C: Firmware updates
Topic D: BIOS and POST troubleshooting

3. BIOS Software instructions on a chip (firmware)
Enable basic computer operations
Input/output with standard devices
Flashing the BIOS
BIOS shadowing

4. CMOS Storage area for BIOS configuration information Battery backed up
Modify using setup utility

5. CMOS battery

6. CMOS setup utility access
Press key combination during boot
Delete F1
Insert
Alt+S
Boot with setup floppy
Press Reset button twice

7. Typical CMOS configurations
Date and time
CPU options
Floppy drive options
Hard drive options
Serial port options
Parallel port options
Enable or disable integrated devices
Enable or disable hardware support for Plug and Play
Power management options
Enable or disable hardware-based virus detection
Boot password

8. Updating your PC’s BIOS settings
Activity A-1
Updating your PC’s BIOS settings

9. Topic B Topic A: BIOS and CMOS Topic B: The POST process
Topic C: Firmware updates
Topic D: BIOS and POST troubleshooting

10. POST process BIOS tests core hardware BIOS tests video subsystem
BIOS identifies itself, including its:
Version
Manufacturer
Date
BIOS tests main system memory

11. Beep codes 1 short beep = No problems found
3 long beeps = Keyboard error
8 short beeps = Video adapter memory problems
9 short beeps = BIOS problem
1 long + 3 short beeps = Memory error

12. Numeric codes 151 = Real time clock failure 161 = Bad CMOS battery
162 = Configuration mismatch
164 = Memory size mismatch
201 or any 20# = Memory failure
1762 = Hard drive configuration error

13. Observing the POST process
Activity B-1
Observing the POST process

14. Boot process You turn on the power
Timer chip sends reset signals to CPU to prevent booting
Power supply performs internal checks, sends Power_Good signal to CPU
Timer stops sending reset signals to the CPU
CPU loads the BIOS and BIOS extensions
BIOS checks whether this is a cold or warm boot
continued

15. Boot process, continued
If cold boot, BIOS performs the POST procedure
BIOS reads CMOS and configures devices
Plug and Play devices detected and configured
BIOS determines which drive to boot from
BIOS reads the master boot record from drive
The OS takes over, completes the boot process

16. Topic C Topic A: BIOS and CMOS Topic B: The POST process
Topic C: Firmware updates
Topic D: BIOS and POST troubleshooting

17. BIOS updates Device problems identified as BIOS problems
Device problems that you can attribute to no other cause
Need to use new hardware options that are not supported by your BIOS

18. BIOS version

19. Flashing the BIOS Determine your current BIOS version
Determine if a new BIOS version is available
Download the new BIOS version installation file
If necessary, download BIOS flashing utility from your PC manufacturer's web site
Close all open applications
Open the flashing utility and follow its instructions to update your BIOS.
Restart your PC when prompted

20. Updating the BIOS in your PC (Optional)
Activity C-1
Updating the BIOS in your PC (Optional)

21. Minimizing BIOS upgrade risks
Don't update your BIOS unless you must
Never turn off your computer during a BIOS update
Make sure to use the correct BIOS flash utility
Follow the flash utility's instructions exactly
Backing up your old BIOS before updating it (flashing utility provides this function)

22. Recovering from failed update
Restore BIOS backup
Boot from a floppy disk containing the correct BIOS and flash utility
Set the Flash recovery jumper switch on the motherboard to reset BIOS to default
Replace the BIOS chip

23. Topic D Topic A: BIOS and CMOS Topic B: The POST process
Topic C: Firmware updates
Topic D: BIOS and POST troubleshooting

24. Bad CMOS battery Older PCs – non-replaceable battery
Newer PCs – held in socket with retaining clips

25. Replacing the CMOS battery
Activity D-1
Replacing the CMOS battery

26. BIOS related symptoms Devices misidentified
Wrong memory size reported during POST or available after booting
Hard drive inaccessible
System won’t boot from hard drive
System boots from the wrong device
Date and time incorrect or reset after powering off the computer

27. POST related symptoms
No video, instead your computer sounds 8 short beeps
The system emits three long beeps
The system emits one long beep and then three short beeps
POST code 162 is displayed
POST code 164 is displayed

28. CMOS related symptoms
The error message “Non-system disk or disk error” is displayed
The error message “Display Type Mismatch” is displayed
The error message “Memory size mismatch” is displayed
The error message “CMOS checksum failure” is displayed

29. Troubleshooting BIOS and POST related problems
Activity D-2
Troubleshooting BIOS and POST related problems

30. Unit summary
Accessed the BIOS setup utility and modified hardware configuration values
Explained the POST and boot processes
Installed a BIOS update
Resolved BIOS and POST-related problems