the basic input/output system unit objectives: access the bios setup utility, change hardware...

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