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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

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Topic A

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

troubleshooting

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BIOS

Software instructions on a chip (firmware)

Enable basic computer operations– Input/output with standard devices

Flashing the BIOS BIOS shadowing

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CMOS

Storage area for BIOS configuration information

Battery backed up Modify using setup utility

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CMOS battery

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CMOS setup utility access

Press key combination during boot– Delete– F1– Insert– Alt+S

Boot with setup floppy Press Reset button twice

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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

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Activity A-1

Updating your PC’s BIOS settings

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Topic B

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

troubleshooting

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POST process

1. BIOS tests core hardware

2. BIOS tests video subsystem

3. BIOS identifies itself, including its: Version Manufacturer Date

4. BIOS tests main system memory

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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

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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

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Activity B-1

Observing the POST process

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Boot process

1. You turn on the power2. Timer chip sends reset signals to

CPU to prevent booting3. Power supply performs internal

checks, sends Power_Good signal to CPU

4. Timer stops sending reset signals to the CPU

5. CPU loads the BIOS and BIOS extensions

6. BIOS checks whether this is a cold or warm boot

continued

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Boot process, continued

7. If cold boot, BIOS performs the POST procedure

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.The OS takes over, completes the boot process

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Topic C

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

troubleshooting

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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

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BIOS version

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Flashing the BIOS

1. Determine your current BIOS version

2. Determine if a new BIOS version is available

3. Download the new BIOS version installation file

4. If necessary, download BIOS flashing utility from your PC manufacturer's web site

5. Close all open applications

6. Open the flashing utility and follow its instructions to update your BIOS.

7. Restart your PC when prompted

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Activity C-1

Updating the BIOS in your PC (Optional)

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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)

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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

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Topic D

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

troubleshooting

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Bad CMOS battery

Older PCs – non-replaceable battery Newer PCs – held in socket with

retaining clips

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Activity D-1

Replacing the CMOS battery

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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

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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

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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

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Activity D-2

Troubleshooting BIOS and POSTrelated problems

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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