the basic input/output system unit objectives: access the bios setup utility, change hardware...
TRANSCRIPT
The Basic Input/Output System
Unit objectives: Access the BIOS setup utility, change
hardware configuration values, and research BIOS updates
Explain the POST and boot processes; and identify the symptoms of, probable causes of, and potential solutions to problems with the BIOS and POST
Topic A
Topic A: The BIOS and CMOS Topic B: The POST and boot
processes
Firmware
Gray area between hardware and software
Software written permanently or semi-permanently to a computer chip
Used to control electronic devices Implemented in PC with BIOS and
CMOS
BIOS
Basic Input/Output System A set of software instructions stored
on a chip on the motherboard Enables basic computer functions Common BIOS manufacturers:
– AMI– AWARD– MR BIOS– PHOENIX
Many use shadowing
CMOS
Area of memory that stores BIOS configuration information
Battery provides power to CMOS Type of computer chip:
complementary metal oxide semiconductor
Can maintain information without a supply of power
CMOS battery
CMOS configuration
Configure with system setup utility– Built in BIOS– Locate on separate hard disk partition– Stored on disc
Access to utility varies by manufacturer
List of CMOS access keys:– http://murfsgarage.cybertechhelp.com/
cmossetup.htm
CMOS configurable settings
Date and time CPU options Optical drive options Floppy drive options Hard drive options Serial port options Parallel port options Integrated devices Plug and Play
continued
CMOS settings, continued
Power management options Virus detection Boot password
Activity A-1
Updating your PC’s BIOS settings
BIOS updates
BIOS implemented either in:– ROM: Programmed at factory – Flash memory: Can update, “flash,” the BIOS
Update if you:– Have device problems or other bugs that PC
manufacturer says are caused by BIOS problems
– Have device problems that can’t be attributed to anything else; have exhausted all other troubleshooting avenues
– Need to use new hardware options that are supported by motherboard but not by BIOS
BIOS update sources
Links to BIOS updates and flashing utilities on PC manufacturer’s Web site
BIOS is tailored by each PC manufacturer
Don’t go to BIOS manufacturer’s Web site
Determining the BIOS version
1. Open System Information
2. Record BIOS Version/Date field value
3. If present, record SMBIOS field value
Flashing the BIOS
1. Determine current BIOS version
2. Go to PC manufacturer’s Web support pages
3. Compare available updates with current version
4. Download new BIOS version
5. Download flashing utility
6. Close all open windows
7. Open flashing utility; follow instructions
8. Restart PC
BIOS update guidelines
Don’t update your BIOS unless you must
Never turn off your computer during a BIOS update– Connect to a UPS
Use the correct BIOS flash utility Follow instructions exactly Back up BIOS if possible
Recovering from a failed update
Use BIOS backup to restore previous version
Use “boot block” Use flash recovery jumper switch Obtain new BIOS chip
Activity A-2
Researching BIOS updates for your PC
Bad CMOS battery
BIOS data retained due to CMOS battery
Older PCs had a soldered battery—not replaceable
Newer PCs have removable battery
Low battery errors
Loss of time or date at boot CMOS Read Error CMOS checksum error CMOS Battery Failure
Replacing the CMOS battery
1. Record custom CMOS setting values2. Power down; open your computer’s chassis3. If necessary, remove cables to allow battery access4. Gently slide the battery out of its compartment5. If necessary, discharge the CMOS memory using
motherboard jumpers6. Insert the new battery into the holder7. Reconnect any cables you disconnected to gain
access to the battery8. Close the PCs chassis9. Reconnect any cables and power cord10.Reboot. Enter correct date and time11.Access BIOS to reset custom values
Activity A-3
Replacing the CMOS battery
Topic B
Topic A: The BIOS and CMOS Topic B: The POST and boot
processes
POST process
Power-on self test1. BIOS tests core hardware
2. BIOS tests video subsystem
3. BIOS identifies itself, including its: Version Manufacturer Date
4. BIOS tests main system memory
Beep codes
Inform user of errors before display is loaded
Vary by manufacturer www.computerhope.com/beep.htm Common 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
Numeric codes
Informs user of errors after display is loaded
Vary by manufacturer IBM numeric code examples:
– 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
Activity B-1
Observing the POST process
The boot process
1. You turn on the power
2. Timer chip sends reset signals to CPU to prevent booting
3. Power supply performs internal checks; sends Power_Good signal to CPU
4. Timer stops sending reset signals to CPU
5. CPU loads BIOS and BIOS extensions
6. BIOS checks whether this is a cold or warm boot
continued
The boot process, continued
7. If cold boot, BIOS performs POST
8. BIOS reads CMOS and configures devices
9. Plug and Play devices detected and configured
10. BIOS determines which drive to boot from
11. BIOS reads the master boot record from drive
12. OS takes over and completes the boot process
Boot devices
Used to load operating system Current:
– Internal hard disk– Optical drive: CD or DVD– USB drive: flash drive or external hard disk or
optical drive– Network drive, using a PXE network interface
card
Older:– Floppy disk drive– SCSI device– Zip drive
Boot devices in the system BIOS
Activity B-2
Checking the boot order
BIOS-related problems
Devices misidentified Wrong memory size reported during
POST or available during booting Hard drive inaccessible System won’t boot from hard drive System boots from the wrong device Date and time incorrect or reset after
computer is turned off
POST-related problems
There’s no video; instead, the computer sounds 8 short beeps
The system emits 3 long beeps The system emits 1 long and 3 short
beeps POST code 162 is displayed POST code 164 is displayed
CMOS-related problems
Error messages: Non-system disk or disk error Display type mismatch Memory size mismatch CMOS checksum failure
Activity B-3
Troubleshooting BIOS and POST problems
Unit summary
Accessed the BIOS setup utility, changed hardware configuration values, and researched BIOS updates
Explained the POST and boot processes; and identified the symptoms of, probable causes of, and potential solutions to problems with the BIOS and POST