troubleshooting guide dr. aiman h. el-maleh computer engineering department dr. aiman h. el-maleh...

Troubleshooting GuideTroubleshooting GuideTroubleshooting GuideTroubleshooting Guide

Dr. Aiman H. El-MalehDr. Aiman H. El-Maleh

Computer Engineering DepartmentComputer Engineering Department

Dr. Aiman H. El-MalehDr. Aiman H. El-Maleh

Computer Engineering DepartmentComputer Engineering Department

2 COE-KFUPMCOE-KFUPM

OutlineOutlineOutlineOutline

Troubleshooting and your Mental StateTroubleshooting and your Mental State Steps to Take First When TroubleshootingSteps to Take First When Troubleshooting Knowing Your Operating SystemKnowing Your Operating System

• System BIOSSystem BIOS• Software LayersSoftware Layers• OS ComponentsOS Components• Boot ProcessBoot Process• How OS Loads/StartsHow OS Loads/Starts

Hardware Vs. Software ProblemsHardware Vs. Software Problems General Diagnostic TechniquesGeneral Diagnostic Techniques Diagnostic, Troubleshooting and Repair ToolsDiagnostic, Troubleshooting and Repair Tools Hardware Troubleshooting FlowchartHardware Troubleshooting Flowchart SummarySummary

Troubleshooting and your Mental StateTroubleshooting and your Mental State Steps to Take First When TroubleshootingSteps to Take First When Troubleshooting Knowing Your Operating SystemKnowing Your Operating System

• System BIOSSystem BIOS• Software LayersSoftware Layers• OS ComponentsOS Components• Boot ProcessBoot Process• How OS Loads/StartsHow OS Loads/Starts

Hardware Vs. Software ProblemsHardware Vs. Software Problems General Diagnostic TechniquesGeneral Diagnostic Techniques Diagnostic, Troubleshooting and Repair ToolsDiagnostic, Troubleshooting and Repair Tools Hardware Troubleshooting FlowchartHardware Troubleshooting Flowchart SummarySummary


Troubleshooting and your Mental Troubleshooting and your Mental StateStateTroubleshooting and your Mental Troubleshooting and your Mental StateState Don't Panic or Overestimate the Magnitude of the Don't Panic or Overestimate the Magnitude of the

ProblemProblem Don't Jump to the Solution Before You Understand the Don't Jump to the Solution Before You Understand the

ProblemProblem Don't Be StubbornDon't Be Stubborn Keep an Open MindKeep an Open Mind Give Yourself TimeGive Yourself Time Be Wary of FatigueBe Wary of Fatigue If You're Stuck, Try Using Your "Background If You're Stuck, Try Using Your "Background

Processing Capabilities“Processing Capabilities“ Two Heads are Better Than OneTwo Heads are Better Than One It Isn't Personal...It Isn't Personal...

Don't Panic or Overestimate the Magnitude of the Don't Panic or Overestimate the Magnitude of the ProblemProblem

Don't Jump to the Solution Before You Understand the Don't Jump to the Solution Before You Understand the ProblemProblem

Don't Be StubbornDon't Be Stubborn Keep an Open MindKeep an Open Mind Give Yourself TimeGive Yourself Time Be Wary of FatigueBe Wary of Fatigue If You're Stuck, Try Using Your "Background If You're Stuck, Try Using Your "Background

Processing Capabilities“Processing Capabilities“ Two Heads are Better Than OneTwo Heads are Better Than One It Isn't Personal...It Isn't Personal...


Steps to Take First When Steps to Take First When TroubleshootingTroubleshootingSteps to Take First When Steps to Take First When TroubleshootingTroubleshooting Let the Vendor Do the Work!Let the Vendor Do the Work!

• Take advantage of warrantyTake advantage of warranty Scan For VirusesScan For Viruses

• use whatever antivirus software you own to do a full scan of use whatever antivirus software you own to do a full scan of the systemthe system

• use a clean boot floppy if possibleuse a clean boot floppy if possible Read the DocumentationRead the Documentation

• Many, if not most problems are a result of hardware or Many, if not most problems are a result of hardware or software that has just been installed into the PCsoftware that has just been installed into the PC

Double-Check Any Recent ChangesDouble-Check Any Recent Changes• having a problem with your PC that was not present before a having a problem with your PC that was not present before a

change to the system, the chances are 99% that the change change to the system, the chances are 99% that the change is the cause of the problemis the cause of the problem

Simplify, Simplify, SimplifySimplify, Simplify, Simplify

Let the Vendor Do the Work!Let the Vendor Do the Work!• Take advantage of warrantyTake advantage of warranty

Scan For VirusesScan For Viruses• use whatever antivirus software you own to do a full scan of use whatever antivirus software you own to do a full scan of

the systemthe system• use a clean boot floppy if possibleuse a clean boot floppy if possible

Read the DocumentationRead the Documentation• Many, if not most problems are a result of hardware or Many, if not most problems are a result of hardware or

software that has just been installed into the PCsoftware that has just been installed into the PC Double-Check Any Recent ChangesDouble-Check Any Recent Changes

• having a problem with your PC that was not present before a having a problem with your PC that was not present before a change to the system, the chances are 99% that the change change to the system, the chances are 99% that the change is the cause of the problemis the cause of the problem

Simplify, Simplify, SimplifySimplify, Simplify, Simplify


Knowing Your Operating SystemKnowing Your Operating SystemKnowing Your Operating SystemKnowing Your Operating System

Best troubleshooter knows entire system - Hardware Best troubleshooter knows entire system - Hardware and Softwareand Software

PCsPCs• how DOS & Win95 (Win98) boothow DOS & Win95 (Win98) boot

• how they interface with hardwarehow they interface with hardware

Win95 & DOS share same structure on diskWin95 & DOS share same structure on disk• few enhancement to directory structure in Win95 and Win98few enhancement to directory structure in Win95 and Win98


PCsPCs• how DOS & Win95 (Win98) boothow DOS & Win95 (Win98) boot

• how they interface with hardwarehow they interface with hardware

Win95 & DOS share same structure on diskWin95 & DOS share same structure on disk• few enhancement to directory structure in Win95 and Win98few enhancement to directory structure in Win95 and Win98


System BIOSSystem BIOSSystem BIOSSystem BIOS

A set of programs always present in systemA set of programs always present in system BIOS routines most primitive in a computerBIOS routines most primitive in a computer

• Talks directly to system hardware Talks directly to system hardware

• Hardware specific - must know exact port address and control Hardware specific - must know exact port address and control bit configuration for I/O devicesbit configuration for I/O devices

BIOS supplied by computer manufacturer and resides BIOS supplied by computer manufacturer and resides in ROMin ROM

Provides services to O.S. or applicationProvides services to O.S. or application Enables O.S. to be written to a standard interfaceEnables O.S. to be written to a standard interface

A set of programs always present in systemA set of programs always present in system BIOS routines most primitive in a computerBIOS routines most primitive in a computer

• Talks directly to system hardware Talks directly to system hardware

• Hardware specific - must know exact port address and control Hardware specific - must know exact port address and control bit configuration for I/O devicesbit configuration for I/O devices

BIOS supplied by computer manufacturer and resides BIOS supplied by computer manufacturer and resides in ROMin ROM

Provides services to O.S. or applicationProvides services to O.S. or application Enables O.S. to be written to a standard interfaceEnables O.S. to be written to a standard interface


Software LayersSoftware LayersSoftware LayersSoftware Layers

System HardwareSystem Hardware

BIOSBIOS

Operating SystemOperating System

Application ProgramApplication Program

Non-standard interfaceNon-standard interface

Standard interfaceStandard interface

Standard interfaceStandard interface


DOS/Windows ComponentsDOS/Windows ComponentsDOS/Windows ComponentsDOS/Windows Components

Two primary components:Two primary components:• I/O system and ShellI/O system and Shell

I/O SystemI/O System• 2 files in DOS: IO.SYS and MSDOS.SYS2 files in DOS: IO.SYS and MSDOS.SYS

• 1 file in Win95: IO.SYS1 file in Win95: IO.SYS

• loaded when DOS/Win95 bootsloaded when DOS/Win95 boots

Shell - portion with which users interactShell - portion with which users interact

Two primary components:Two primary components:• I/O system and ShellI/O system and Shell

I/O SystemI/O System• 2 files in DOS: IO.SYS and MSDOS.SYS2 files in DOS: IO.SYS and MSDOS.SYS

• 1 file in Win95: IO.SYS1 file in Win95: IO.SYS

• loaded when DOS/Win95 bootsloaded when DOS/Win95 boots

Shell - portion with which users interactShell - portion with which users interact


DOS/Windows ComponentsDOS/Windows Components

IO.SYSIO.SYS• interacts directly with devices and BIOSinteracts directly with devices and BIOS

• remains in memoryremains in memory

MSDOS.SYSMSDOS.SYS

• Contains disk handling programsContains disk handling programs

• remains in memoryremains in memory IO.SYS in WindowsIO.SYS in Windows

• contains all code in IO.SYS and MSDOS.SYScontains all code in IO.SYS and MSDOS.SYS


Boot ProcessBoot Process

Method by which PC becomes operationalMethod by which PC becomes operational Error messages can come from:Error messages can come from:

• BIOSBIOS

• boot sectorboot sector

• System filesSystem files

• Device driversDevice drivers

• Shell program (not in WIN95)Shell program (not in WIN95)

• Programs run by AUTOEXEC.BAT (not in WIN95)Programs run by AUTOEXEC.BAT (not in WIN95)

• WindowsWindows


How DOS/Windows StartsHow DOS/Windows StartsHow DOS/Windows StartsHow DOS/Windows Starts

1.1. Power supply performs a self-test. Power supply performs a self-test.• When voltages and current levels acceptable, sends When voltages and current levels acceptable, sends

Power_Good Power_Good

2.2. Power_Good resets processor Power_Good resets processor

3.3. Execute ROM BIOS code from location FFFF0h, right at Execute ROM BIOS code from location FFFF0h, right at the end of the system memorythe end of the system memory

4.4. BIOS performs the power-on self test (POST) of central BIOS performs the power-on self test (POST) of central hardwarehardware• Errors indicated by audio beep codesErrors indicated by audio beep codes

5.5. Performs a video ROM scan looking for the video Performs a video ROM scan looking for the video card's built in BIOS program and runs it. card's built in BIOS program and runs it. • This BIOS is normally found at location C000h in memory. This BIOS is normally found at location C000h in memory.

1.1. Power supply performs a self-test. Power supply performs a self-test.• When voltages and current levels acceptable, sends When voltages and current levels acceptable, sends

Power_Good Power_Good

2.2. Power_Good resets processor Power_Good resets processor

3.3. Execute ROM BIOS code from location FFFF0h, right at Execute ROM BIOS code from location FFFF0h, right at the end of the system memorythe end of the system memory

4.4. BIOS performs the power-on self test (POST) of central BIOS performs the power-on self test (POST) of central hardwarehardware• Errors indicated by audio beep codesErrors indicated by audio beep codes

5.5. Performs a video ROM scan looking for the video Performs a video ROM scan looking for the video card's built in BIOS program and runs it. card's built in BIOS program and runs it. • This BIOS is normally found at location C000h in memory. This BIOS is normally found at location C000h in memory.



6.6. The BIOS then looks for other devices' ROMs to see if The BIOS then looks for other devices' ROMs to see if any of them have BIOSes.any of them have BIOSes.• Normally, the IDE/ATA hard disk BIOS will be found at Normally, the IDE/ATA hard disk BIOS will be found at

C8000h and executed. If any other device BIOSes are C8000h and executed. If any other device BIOSes are found, they are executed as well. found, they are executed as well.

7.7. The BIOS displays its startup screen. The BIOS displays its startup screen. • The BIOS Manufacturer and Version Number.The BIOS Manufacturer and Version Number. • The BIOS DateThe BIOS Date• Setup Program KeySetup Program Key• System LogoSystem Logo• The "Energy Star" LogoThe "Energy Star" Logo• The BIOS Serial NumberThe BIOS Serial Number

8.8. The BIOS does more tests on the system, including the The BIOS does more tests on the system, including the memory count-up test which you see on the screenmemory count-up test which you see on the screen• Errors by audio and displayed messagesErrors by audio and displayed messages

6.6. The BIOS then looks for other devices' ROMs to see if The BIOS then looks for other devices' ROMs to see if any of them have BIOSes.any of them have BIOSes.• Normally, the IDE/ATA hard disk BIOS will be found at Normally, the IDE/ATA hard disk BIOS will be found at

C8000h and executed. If any other device BIOSes are C8000h and executed. If any other device BIOSes are found, they are executed as well. found, they are executed as well.

7.7. The BIOS displays its startup screen. The BIOS displays its startup screen. • The BIOS Manufacturer and Version Number.The BIOS Manufacturer and Version Number. • The BIOS DateThe BIOS Date• Setup Program KeySetup Program Key• System LogoSystem Logo• The "Energy Star" LogoThe "Energy Star" Logo• The BIOS Serial NumberThe BIOS Serial Number

8.8. The BIOS does more tests on the system, including the The BIOS does more tests on the system, including the memory count-up test which you see on the screenmemory count-up test which you see on the screen• Errors by audio and displayed messagesErrors by audio and displayed messages



9. 9. The BIOS performs a "system inventory" of sorts, The BIOS performs a "system inventory" of sorts, doing more tests to determine what sort of hardware is doing more tests to determine what sort of hardware is in the system. in the system.

10. 10. If the BIOS supports the Plug and Play standard, it If the BIOS supports the Plug and Play standard, it will detect and configure Plug and Play devices at this will detect and configure Plug and Play devices at this time and display a message on the screen for each time and display a message on the screen for each one it finds.one it finds.

11.11. The BIOS will display a summary screen about your The BIOS will display a summary screen about your system's configuration. system's configuration. • Processor (CPU) TypeProcessor (CPU) Type• CoprocessorCoprocessor• Clock SpeedClock Speed• Floppy Drive AFloppy Drive A• Floppy Drive BFloppy Drive B• IDE/ATA DrivesIDE/ATA Drives• Base Memory SizeBase Memory Size

9. 9. The BIOS performs a "system inventory" of sorts, The BIOS performs a "system inventory" of sorts, doing more tests to determine what sort of hardware is doing more tests to determine what sort of hardware is in the system. in the system.

10. 10. If the BIOS supports the Plug and Play standard, it If the BIOS supports the Plug and Play standard, it will detect and configure Plug and Play devices at this will detect and configure Plug and Play devices at this time and display a message on the screen for each time and display a message on the screen for each one it finds.one it finds.

11.11. The BIOS will display a summary screen about your The BIOS will display a summary screen about your system's configuration. system's configuration. • Processor (CPU) TypeProcessor (CPU) Type• CoprocessorCoprocessor• Clock SpeedClock Speed• Floppy Drive AFloppy Drive A• Floppy Drive BFloppy Drive B• IDE/ATA DrivesIDE/ATA Drives• Base Memory SizeBase Memory Size



• Extended Memory SizeExtended Memory Size

• Cache SizeCache Size

• Memory Type and ConfigurationMemory Type and Configuration

• Display TypeDisplay Type

• Serial Port(s):Serial Port(s):

• Parallel Port(s):Parallel Port(s):

• Plug and Play DevicesPlug and Play Devices

12. 12. The BIOS begins the search for a drive to boot from.The BIOS begins the search for a drive to boot from.• Most modern BIOSes contain a setting that controls if the Most modern BIOSes contain a setting that controls if the

system should first try to boot from the floppy disk (A:) or first system should first try to boot from the floppy disk (A:) or first try the hard disk (C:). try the hard disk (C:).

• Some BIOSes will even let you boot from your CD-ROM Some BIOSes will even let you boot from your CD-ROM drive or other devices, depending on the boot sequence drive or other devices, depending on the boot sequence BIOS setting. BIOS setting.

• Extended Memory SizeExtended Memory Size

• Cache SizeCache Size

• Memory Type and ConfigurationMemory Type and Configuration

• Display TypeDisplay Type

• Serial Port(s):Serial Port(s):

• Parallel Port(s):Parallel Port(s):

• Plug and Play DevicesPlug and Play Devices

12. 12. The BIOS begins the search for a drive to boot from.The BIOS begins the search for a drive to boot from.• Most modern BIOSes contain a setting that controls if the Most modern BIOSes contain a setting that controls if the

system should first try to boot from the floppy disk (A:) or first system should first try to boot from the floppy disk (A:) or first try the hard disk (C:). try the hard disk (C:).

• Some BIOSes will even let you boot from your CD-ROM Some BIOSes will even let you boot from your CD-ROM drive or other devices, depending on the boot sequence drive or other devices, depending on the boot sequence BIOS setting. BIOS setting.



13.13. Having identified its target boot drive, the BIOS looks Having identified its target boot drive, the BIOS looks for boot information to start the operating system for boot information to start the operating system boot process.boot process.• If it is searching a hard disk, it looks for a master boot If it is searching a hard disk, it looks for a master boot

record at cylinder 0, head 0, sector 1 (the first sector on the record at cylinder 0, head 0, sector 1 (the first sector on the disk);disk);

• if it is searching a floppy disk, it looks at the same address if it is searching a floppy disk, it looks at the same address on the floppy disk for a volume boot sector. on the floppy disk for a volume boot sector.

14. 14. If it finds what it is looking for, the BIOS starts the If it finds what it is looking for, the BIOS starts the process of booting the operating system, using the process of booting the operating system, using the information in the boot sector. At this point, the code information in the boot sector. At this point, the code in the boot sector takes over from the BIOS. in the boot sector takes over from the BIOS. • If the first device that the system tries (floppy, hard disk, If the first device that the system tries (floppy, hard disk,

etc.) is not found, the BIOS will then try the next device in etc.) is not found, the BIOS will then try the next device in the boot sequence, and continue until it finds a bootable the boot sequence, and continue until it finds a bootable device. device.

13.13. Having identified its target boot drive, the BIOS looks Having identified its target boot drive, the BIOS looks for boot information to start the operating system for boot information to start the operating system boot process.boot process.• If it is searching a hard disk, it looks for a master boot If it is searching a hard disk, it looks for a master boot

record at cylinder 0, head 0, sector 1 (the first sector on the record at cylinder 0, head 0, sector 1 (the first sector on the disk);disk);

• if it is searching a floppy disk, it looks at the same address if it is searching a floppy disk, it looks at the same address on the floppy disk for a volume boot sector. on the floppy disk for a volume boot sector.

14. 14. If it finds what it is looking for, the BIOS starts the If it finds what it is looking for, the BIOS starts the process of booting the operating system, using the process of booting the operating system, using the information in the boot sector. At this point, the code information in the boot sector. At this point, the code in the boot sector takes over from the BIOS. in the boot sector takes over from the BIOS. • If the first device that the system tries (floppy, hard disk, If the first device that the system tries (floppy, hard disk,

etc.) is not found, the BIOS will then try the next device in etc.) is not found, the BIOS will then try the next device in the boot sequence, and continue until it finds a bootable the boot sequence, and continue until it finds a bootable device. device.



15.15. If no boot device at all can be found, the system will If no boot device at all can be found, the system will normally display an error message and then freeze up normally display an error message and then freeze up the system. the system. • the error message depends entirely on the BIOS, and can the error message depends entirely on the BIOS, and can

be anything from the rather clear "No boot device available" be anything from the rather clear "No boot device available" to the very cryptic "NO ROM BASIC - SYSTEM HALTED". to the very cryptic "NO ROM BASIC - SYSTEM HALTED".

16.16. The BIOS loads the boot code in the master boot The BIOS loads the boot code in the master boot record and transfers control to it. The master boot record and transfers control to it. The master boot record code begins execution. If the boot device is a record code begins execution. If the boot device is a floppy disk, the process continues with step 21. floppy disk, the process continues with step 21.

17.17. The master boot code examines the master partition The master boot code examines the master partition table. It is searching for two things. table. It is searching for two things. • First, it must determine if there is an extended DOS First, it must determine if there is an extended DOS

partition.partition.• Second, it must determine if there is a bootable partition Second, it must determine if there is a bootable partition

specified in the partition table.specified in the partition table.

15.15. If no boot device at all can be found, the system will If no boot device at all can be found, the system will normally display an error message and then freeze up normally display an error message and then freeze up the system. the system. • the error message depends entirely on the BIOS, and can the error message depends entirely on the BIOS, and can

be anything from the rather clear "No boot device available" be anything from the rather clear "No boot device available" to the very cryptic "NO ROM BASIC - SYSTEM HALTED". to the very cryptic "NO ROM BASIC - SYSTEM HALTED".

16.16. The BIOS loads the boot code in the master boot The BIOS loads the boot code in the master boot record and transfers control to it. The master boot record and transfers control to it. The master boot record code begins execution. If the boot device is a record code begins execution. If the boot device is a floppy disk, the process continues with step 21. floppy disk, the process continues with step 21.

17.17. The master boot code examines the master partition The master boot code examines the master partition table. It is searching for two things. table. It is searching for two things. • First, it must determine if there is an extended DOS First, it must determine if there is an extended DOS

partition.partition.• Second, it must determine if there is a bootable partition Second, it must determine if there is a bootable partition

specified in the partition table.specified in the partition table.



18.18. If the master boot code finds an extended partition on If the master boot code finds an extended partition on the disk, it loads the extended partition table that the disk, it loads the extended partition table that describes the first logical volume in the extended describes the first logical volume in the extended partition. partition. • This extended partition table is examined to see if it points to This extended partition table is examined to see if it points to

another extended partition table. another extended partition table. • This process is continued until all of the extended partitions This process is continued until all of the extended partitions

have been loaded and recognized by the system. have been loaded and recognized by the system.

19.19. After loading the extended partition information (if After loading the extended partition information (if any), the code attempts to boot the primary partition any), the code attempts to boot the primary partition that is marked active (bootable). that is marked active (bootable). • If there are no partitions marked active, then the boot If there are no partitions marked active, then the boot

process will terminate with an error. process will terminate with an error. • The error message is often the same one that occurs if the The error message is often the same one that occurs if the

BIOS finds no boot device, and is generally something like BIOS finds no boot device, and is generally something like "No boot device", but can be the infamous "NO ROM BASIC "No boot device", but can be the infamous "NO ROM BASIC - SYSTEM HALTED". - SYSTEM HALTED".

18.18. If the master boot code finds an extended partition on If the master boot code finds an extended partition on the disk, it loads the extended partition table that the disk, it loads the extended partition table that describes the first logical volume in the extended describes the first logical volume in the extended partition. partition. • This extended partition table is examined to see if it points to This extended partition table is examined to see if it points to

another extended partition table. another extended partition table. • This process is continued until all of the extended partitions This process is continued until all of the extended partitions

have been loaded and recognized by the system. have been loaded and recognized by the system.

19.19. After loading the extended partition information (if After loading the extended partition information (if any), the code attempts to boot the primary partition any), the code attempts to boot the primary partition that is marked active (bootable). that is marked active (bootable). • If there are no partitions marked active, then the boot If there are no partitions marked active, then the boot

process will terminate with an error. process will terminate with an error. • The error message is often the same one that occurs if the The error message is often the same one that occurs if the

BIOS finds no boot device, and is generally something like BIOS finds no boot device, and is generally something like "No boot device", but can be the infamous "NO ROM BASIC "No boot device", but can be the infamous "NO ROM BASIC - SYSTEM HALTED". - SYSTEM HALTED".



20.20. If there is a primary partition marked active, the code If there is a primary partition marked active, the code will boot it. The rest of the steps assume this is a DOS will boot it. The rest of the steps assume this is a DOS primary partition. primary partition.

21.21. The volume boot sector is loaded into memory and The volume boot sector is loaded into memory and tested, and the boot code that it contains is given tested, and the boot code that it contains is given control of the remainder of the boot process. control of the remainder of the boot process.

22.22. The volume boot code examines the structures on the The volume boot code examines the structures on the disk that it is booting to ensure that everything is disk that it is booting to ensure that everything is correct and in the right place. If not, the boot process correct and in the right place. If not, the boot process will end in an error here as well. will end in an error here as well.

23.23. The code searches the root directory of the device The code searches the root directory of the device being booted for the operating system files that being booted for the operating system files that contain the operating system. For a system running contain the operating system. For a system running MS-DOS these are the files "MS-DOS these are the files "IO.SYSIO.SYS", "", "MSDOS.SYSMSDOS.SYS" " and "and "COMMAND.COMCOMMAND.COM". ".

20.20. If there is a primary partition marked active, the code If there is a primary partition marked active, the code will boot it. The rest of the steps assume this is a DOS will boot it. The rest of the steps assume this is a DOS primary partition. primary partition.

21.21. The volume boot sector is loaded into memory and The volume boot sector is loaded into memory and tested, and the boot code that it contains is given tested, and the boot code that it contains is given control of the remainder of the boot process. control of the remainder of the boot process.

22.22. The volume boot code examines the structures on the The volume boot code examines the structures on the disk that it is booting to ensure that everything is disk that it is booting to ensure that everything is correct and in the right place. If not, the boot process correct and in the right place. If not, the boot process will end in an error here as well. will end in an error here as well.

23.23. The code searches the root directory of the device The code searches the root directory of the device being booted for the operating system files that being booted for the operating system files that contain the operating system. For a system running contain the operating system. For a system running MS-DOS these are the files "MS-DOS these are the files "IO.SYSIO.SYS", "", "MSDOS.SYSMSDOS.SYS" " and "and "COMMAND.COMCOMMAND.COM". ".



24.24. If the operating system files are not found, the boot If the operating system files are not found, the boot program will display an error message, which is program will display an error message, which is usually something like "Non-system disk or disk error usually something like "Non-system disk or disk error - Replace and press any key when ready". - Replace and press any key when ready".

25.25. If the operating system files are found, the boot If the operating system files are found, the boot program will load them into memory and transfer program will load them into memory and transfer control to them.control to them.• First, IO.SYS is loaded and its code executed. First, IO.SYS is loaded and its code executed. • IO.SYS will then executed MSDOS.SYS (in pure DOS IO.SYS will then executed MSDOS.SYS (in pure DOS

systems--MSDOS.SYS is just a text file in Windows 95 and systems--MSDOS.SYS is just a text file in Windows 95 and later.) later.)

• Then the more complete operating system code loads and Then the more complete operating system code loads and initializes the rest of the operating system structures. For initializes the rest of the operating system structures. For MS-DOS, this means loading the command interpreter MS-DOS, this means loading the command interpreter (COMMAND.COM) and then reading and interpreting the (COMMAND.COM) and then reading and interpreting the contents of the CONFIG.SYS and AUTOEXEC.BAT system contents of the CONFIG.SYS and AUTOEXEC.BAT system control files. control files.

24.24. If the operating system files are not found, the boot If the operating system files are not found, the boot program will display an error message, which is program will display an error message, which is usually something like "Non-system disk or disk error usually something like "Non-system disk or disk error - Replace and press any key when ready". - Replace and press any key when ready".

25.25. If the operating system files are found, the boot If the operating system files are found, the boot program will load them into memory and transfer program will load them into memory and transfer control to them.control to them.• First, IO.SYS is loaded and its code executed. First, IO.SYS is loaded and its code executed. • IO.SYS will then executed MSDOS.SYS (in pure DOS IO.SYS will then executed MSDOS.SYS (in pure DOS

systems--MSDOS.SYS is just a text file in Windows 95 and systems--MSDOS.SYS is just a text file in Windows 95 and later.) later.)

• Then the more complete operating system code loads and Then the more complete operating system code loads and initializes the rest of the operating system structures. For initializes the rest of the operating system structures. For MS-DOS, this means loading the command interpreter MS-DOS, this means loading the command interpreter (COMMAND.COM) and then reading and interpreting the (COMMAND.COM) and then reading and interpreting the contents of the CONFIG.SYS and AUTOEXEC.BAT system contents of the CONFIG.SYS and AUTOEXEC.BAT system control files. control files.



• Filing system is activeFiling system is active

• IO.SYS reads CONFIG.SYS and SYSTEM.DATIO.SYS reads CONFIG.SYS and SYSTEM.DAT• CONFIG.SYS processes in orderCONFIG.SYS processes in order• DEVICE and INSTALL statementsDEVICE and INSTALL statements• SHELL statements. If no SHELL, COMMAND.COM is loaded SHELL statements. If no SHELL, COMMAND.COM is loaded • In Win 95, COMMAND.COM is loaded only if AUTOEXEC.BAT In Win 95, COMMAND.COM is loaded only if AUTOEXEC.BAT

existsexists

• AUTOEXEC.BAT executedAUTOEXEC.BAT executed

• IO.SYS loads (in WIn95)IO.SYS loads (in WIn95)• HIMEM.SYS, IFSHLP.SYS, SETVER.EXE, and WIN.COM.HIMEM.SYS, IFSHLP.SYS, SETVER.EXE, and WIN.COM.

• Filing system is activeFiling system is active

• IO.SYS reads CONFIG.SYS and SYSTEM.DATIO.SYS reads CONFIG.SYS and SYSTEM.DAT• CONFIG.SYS processes in orderCONFIG.SYS processes in order• DEVICE and INSTALL statementsDEVICE and INSTALL statements• SHELL statements. If no SHELL, COMMAND.COM is loaded SHELL statements. If no SHELL, COMMAND.COM is loaded • In Win 95, COMMAND.COM is loaded only if AUTOEXEC.BAT In Win 95, COMMAND.COM is loaded only if AUTOEXEC.BAT

existsexists

• AUTOEXEC.BAT executedAUTOEXEC.BAT executed

• IO.SYS loads (in WIn95)IO.SYS loads (in WIn95)• HIMEM.SYS, IFSHLP.SYS, SETVER.EXE, and WIN.COM.HIMEM.SYS, IFSHLP.SYS, SETVER.EXE, and WIN.COM.


Hardware vs. Software ProblemsHardware vs. Software ProblemsHardware vs. Software ProblemsHardware vs. Software Problems

Software problems often caused bySoftware problems often caused by• device drivers, memory-resident programsdevice drivers, memory-resident programs

• loaded by CONFIG.SYS and AUTOEXEC.BATloaded by CONFIG.SYS and AUTOEXEC.BAT

To see if software problem:To see if software problem:• boot system from a system disk with none of these filesboot system from a system disk with none of these files

• restore drivers and memory resident programs one at a timerestore drivers and memory resident programs one at a time

• in Win95, also SYSTEM.DATin Win95, also SYSTEM.DAT

Software problems often caused bySoftware problems often caused by• device drivers, memory-resident programsdevice drivers, memory-resident programs

• loaded by CONFIG.SYS and AUTOEXEC.BATloaded by CONFIG.SYS and AUTOEXEC.BAT

To see if software problem:To see if software problem:• boot system from a system disk with none of these filesboot system from a system disk with none of these files

• restore drivers and memory resident programs one at a timerestore drivers and memory resident programs one at a time

• in Win95, also SYSTEM.DATin Win95, also SYSTEM.DAT


Hardware TroubleshootingHardware TroubleshootingHardware TroubleshootingHardware Troubleshooting

Work from most likely to cause problem to leastWork from most likely to cause problem to least Check environmentCheck environment

• incoming power, temperature fluctuations, humidity, static incoming power, temperature fluctuations, humidity, static electricityelectricity

Try to solve intermittent problemsTry to solve intermittent problems• use hair dryer to warm up motherboarduse hair dryer to warm up motherboard

• spray the suspected component cooler or freonspray the suspected component cooler or freon

Three types of programs can helpThree types of programs can help• POST (Power-On Self Test)POST (Power-On Self Test)

• Manufacturer supplied diagnostics softwareManufacturer supplied diagnostics software

• Advanced diagnostics softwareAdvanced diagnostics software

Work from most likely to cause problem to leastWork from most likely to cause problem to least Check environmentCheck environment

• incoming power, temperature fluctuations, humidity, static incoming power, temperature fluctuations, humidity, static electricityelectricity

Try to solve intermittent problemsTry to solve intermittent problems• use hair dryer to warm up motherboarduse hair dryer to warm up motherboard

• spray the suspected component cooler or freonspray the suspected component cooler or freon

Three types of programs can helpThree types of programs can help• POST (Power-On Self Test)POST (Power-On Self Test)

• Manufacturer supplied diagnostics softwareManufacturer supplied diagnostics software

• Advanced diagnostics softwareAdvanced diagnostics software


General Diagnostic TechniquesGeneral Diagnostic TechniquesGeneral Diagnostic TechniquesGeneral Diagnostic Techniques

Get to the Root Cause: Ask "Why" Five TimesGet to the Root Cause: Ask "Why" Five Times• One of the keys to truly solving a problem is to first One of the keys to truly solving a problem is to first

understand itunderstand it

• people are quick to people are quick to jump to solve a problemjump to solve a problem before they really before they really understand what it isunderstand what it is

• The goal is not to correct effects of the problem, but to find The goal is not to correct effects of the problem, but to find out the root cause of why the problem is occurring so that we out the root cause of why the problem is occurring so that we can ensure that it will not happen in the futurecan ensure that it will not happen in the future

• avoid "quick fix" solutions that are really just band-aids and avoid "quick fix" solutions that are really just band-aids and don't resolve anythingdon't resolve anything

Get to the Root Cause: Ask "Why" Five TimesGet to the Root Cause: Ask "Why" Five Times• One of the keys to truly solving a problem is to first One of the keys to truly solving a problem is to first

understand itunderstand it

• people are quick to people are quick to jump to solve a problemjump to solve a problem before they really before they really understand what it isunderstand what it is

• The goal is not to correct effects of the problem, but to find The goal is not to correct effects of the problem, but to find out the root cause of why the problem is occurring so that we out the root cause of why the problem is occurring so that we can ensure that it will not happen in the futurecan ensure that it will not happen in the future

• avoid "quick fix" solutions that are really just band-aids and avoid "quick fix" solutions that are really just band-aids and don't resolve anythingdon't resolve anything



• Example: Let's suppose your hard disk is having a Example: Let's suppose your hard disk is having a problem with bad sectors showing upproblem with bad sectors showing up

• The knee-jerk reaction to this happening is "the hard disk is bad, The knee-jerk reaction to this happening is "the hard disk is bad, replace it". replace it".

• WhyWhy are bad sectors showing up when they didn't before?" are bad sectors showing up when they didn't before?" • "The hard disk is being corrupted somehow; something has "The hard disk is being corrupted somehow; something has

changed.“ "changed.“ "WhyWhy?" ?" • "The timing of the system probably has been changed in some "The timing of the system probably has been changed in some

way.“ "way.“ "WhyWhy?" ?" • "Hmm, I installed a new hard drive in that system just last week, "Hmm, I installed a new hard drive in that system just last week,

perhaps it is causing the problem." "perhaps it is causing the problem." "WhyWhy?" ?" • "The hard drive may not have been installed correctly, or "The hard drive may not have been installed correctly, or

perhaps I should have used a different channel. Or maybe it was perhaps I should have used a different channel. Or maybe it was the bus-mastering driver that came with the new drive, the old the bus-mastering driver that came with the new drive, the old drive may not be able to support it". drive may not be able to support it".

• Example: Let's suppose your hard disk is having a Example: Let's suppose your hard disk is having a problem with bad sectors showing upproblem with bad sectors showing up

• The knee-jerk reaction to this happening is "the hard disk is bad, The knee-jerk reaction to this happening is "the hard disk is bad, replace it". replace it".

• WhyWhy are bad sectors showing up when they didn't before?" are bad sectors showing up when they didn't before?" • "The hard disk is being corrupted somehow; something has "The hard disk is being corrupted somehow; something has

changed.“ "changed.“ "WhyWhy?" ?" • "The timing of the system probably has been changed in some "The timing of the system probably has been changed in some

way.“ "way.“ "WhyWhy?" ?" • "Hmm, I installed a new hard drive in that system just last week, "Hmm, I installed a new hard drive in that system just last week,

perhaps it is causing the problem." "perhaps it is causing the problem." "WhyWhy?" ?" • "The hard drive may not have been installed correctly, or "The hard drive may not have been installed correctly, or

perhaps I should have used a different channel. Or maybe it was perhaps I should have used a different channel. Or maybe it was the bus-mastering driver that came with the new drive, the old the bus-mastering driver that came with the new drive, the old drive may not be able to support it". drive may not be able to support it".



• Example: imagine an office that has just had a Example: imagine an office that has just had a catastrophic data loss due to a PC crashing after an catastrophic data loss due to a PC crashing after an electrical stormelectrical storm

• The initially identified cause of this problem was a lack of a UPS The initially identified cause of this problem was a lack of a UPS on the PC, which would have protected the system from the on the PC, which would have protected the system from the electrical stormelectrical storm

• "Remember that the problem here was the "Remember that the problem here was the data lossdata loss, not the , not the crashing of the PC. Why was the data lost?" crashing of the PC. Why was the data lost?"

• "The PC's hard disk crashed." "The PC's hard disk crashed." • ""WhyWhy would that cause the data to be lost?" would that cause the data to be lost?" • "Because we didn't have a backup." "Because we didn't have a backup." • ""WhyWhy wasn't there a backup?" wasn't there a backup?" • "There is a tape backup unit on every PC in the building but very "There is a tape backup unit on every PC in the building but very

few of them are being used." "few of them are being used." "WhyWhy?" ?" • "Because most of the PC users do not know how to use them." "Because most of the PC users do not know how to use them."

""WhyWhy?" ?" • "They have never been given any training in their use." ""They have never been given any training in their use." "WhyWhy?" ?" • "Because we don't have a budget for PC hardware training." "Because we don't have a budget for PC hardware training."

• Example: imagine an office that has just had a Example: imagine an office that has just had a catastrophic data loss due to a PC crashing after an catastrophic data loss due to a PC crashing after an electrical stormelectrical storm

• The initially identified cause of this problem was a lack of a UPS The initially identified cause of this problem was a lack of a UPS on the PC, which would have protected the system from the on the PC, which would have protected the system from the electrical stormelectrical storm

• "Remember that the problem here was the "Remember that the problem here was the data lossdata loss, not the , not the crashing of the PC. Why was the data lost?" crashing of the PC. Why was the data lost?"

• "The PC's hard disk crashed." "The PC's hard disk crashed." • ""WhyWhy would that cause the data to be lost?" would that cause the data to be lost?" • "Because we didn't have a backup." "Because we didn't have a backup." • ""WhyWhy wasn't there a backup?" wasn't there a backup?" • "There is a tape backup unit on every PC in the building but very "There is a tape backup unit on every PC in the building but very

few of them are being used." "few of them are being used." "WhyWhy?" ?" • "Because most of the PC users do not know how to use them." "Because most of the PC users do not know how to use them."

""WhyWhy?" ?" • "They have never been given any training in their use." ""They have never been given any training in their use." "WhyWhy?" ?" • "Because we don't have a budget for PC hardware training." "Because we don't have a budget for PC hardware training."



Be Observant and Look For EvidenceBe Observant and Look For Evidence• subtle signs can provide triggering piece of information that subtle signs can provide triggering piece of information that

leads to discovering the source of a problemleads to discovering the source of a problem

• investigate anything that seems "unusual", "wrong" or investigate anything that seems "unusual", "wrong" or "surprising". "surprising".

Use the Process of EliminationUse the Process of Elimination• all problems with PCs involve more than one component or all problems with PCs involve more than one component or

subsystemsubsystem

• using the process of elimination you can narrow the problem using the process of elimination you can narrow the problem down down

• The key is to make only one change at a time and then see if The key is to make only one change at a time and then see if the problem goes awaythe problem goes away

• first check the most probable sources of the problem, and first check the most probable sources of the problem, and also the things that are easiest to changealso the things that are easiest to change

Be Observant and Look For EvidenceBe Observant and Look For Evidence• subtle signs can provide triggering piece of information that subtle signs can provide triggering piece of information that

leads to discovering the source of a problemleads to discovering the source of a problem

• investigate anything that seems "unusual", "wrong" or investigate anything that seems "unusual", "wrong" or "surprising". "surprising".

Use the Process of EliminationUse the Process of Elimination• all problems with PCs involve more than one component or all problems with PCs involve more than one component or

subsystemsubsystem

• using the process of elimination you can narrow the problem using the process of elimination you can narrow the problem down down

• The key is to make only one change at a time and then see if The key is to make only one change at a time and then see if the problem goes awaythe problem goes away

• first check the most probable sources of the problem, and first check the most probable sources of the problem, and also the things that are easiest to changealso the things that are easiest to change



Do One Upgrade or Assembly Step At a TimeDo One Upgrade or Assembly Step At a Time• Changes made to the system are the most frequent cause of Changes made to the system are the most frequent cause of

problemsproblems

• do not do major software or operating system upgrades at the do not do major software or operating system upgrades at the same time that you make hardware changessame time that you make hardware changes

Make Use of Components That You Know WorkMake Use of Components That You Know Work• extra components can be useful when you are employing extra components can be useful when you are employing

the process of eliminationthe process of elimination to resolve problems to resolve problems

Write Things DownWrite Things Down• Keeping a history of what you discover and what your Keeping a history of what you discover and what your

symptoms are will help you not only with this problem but also symptoms are will help you not only with this problem but also with any future difficultieswith any future difficulties

Do One Upgrade or Assembly Step At a TimeDo One Upgrade or Assembly Step At a Time• Changes made to the system are the most frequent cause of Changes made to the system are the most frequent cause of

problemsproblems

• do not do major software or operating system upgrades at the do not do major software or operating system upgrades at the same time that you make hardware changessame time that you make hardware changes

Make Use of Components That You Know WorkMake Use of Components That You Know Work• extra components can be useful when you are employing extra components can be useful when you are employing

the process of eliminationthe process of elimination to resolve problems to resolve problems

Write Things DownWrite Things Down• Keeping a history of what you discover and what your Keeping a history of what you discover and what your

symptoms are will help you not only with this problem but also symptoms are will help you not only with this problem but also with any future difficultieswith any future difficulties



Determine RepeatabilityDetermine Repeatability• Most problems with a PC fall into one of two categories: either Most problems with a PC fall into one of two categories: either

they are they are repeatablerepeatable or they are or they are intermittentintermittent. . • A repeatable problem is one where the problem occurs all the A repeatable problem is one where the problem occurs all the

time, or always in response to a specific user actiontime, or always in response to a specific user action• Intermittent problems are ones which appear to happen Intermittent problems are ones which appear to happen

spontaneously or randomlyspontaneously or randomly• Intermittent problems are much more difficult to deal withIntermittent problems are much more difficult to deal with

Dealing With Intermittent ProblemsDealing With Intermittent Problems• Intermittent problems seem not to be caused by anything Intermittent problems seem not to be caused by anything

obvious and are not repeatableobvious and are not repeatable• can be extremely difficult and frustrating to diagnosecan be extremely difficult and frustrating to diagnose• you may not be able to systematically work your way towards you may not be able to systematically work your way towards

the ultimate causethe ultimate cause• you may have to employ trial-and-error, making a change and you may have to employ trial-and-error, making a change and

then waiting to see if the problem recursthen waiting to see if the problem recurs

Determine RepeatabilityDetermine Repeatability• Most problems with a PC fall into one of two categories: either Most problems with a PC fall into one of two categories: either

they are they are repeatablerepeatable or they are or they are intermittentintermittent. . • A repeatable problem is one where the problem occurs all the A repeatable problem is one where the problem occurs all the

time, or always in response to a specific user actiontime, or always in response to a specific user action• Intermittent problems are ones which appear to happen Intermittent problems are ones which appear to happen

spontaneously or randomlyspontaneously or randomly• Intermittent problems are much more difficult to deal withIntermittent problems are much more difficult to deal with

Dealing With Intermittent ProblemsDealing With Intermittent Problems• Intermittent problems seem not to be caused by anything Intermittent problems seem not to be caused by anything

obvious and are not repeatableobvious and are not repeatable• can be extremely difficult and frustrating to diagnosecan be extremely difficult and frustrating to diagnose• you may not be able to systematically work your way towards you may not be able to systematically work your way towards

the ultimate causethe ultimate cause• you may have to employ trial-and-error, making a change and you may have to employ trial-and-error, making a change and

then waiting to see if the problem recursthen waiting to see if the problem recurs



Correlation May Not Imply CausationCorrelation May Not Imply Causation• two strange things happening at the same time on your PC, two strange things happening at the same time on your PC,

does not mean that one of them has caused the otherdoes not mean that one of them has caused the other

• Example: you have frequent file system corruption on your Example: you have frequent file system corruption on your hard disk, and you have a lot of system lockups (hangs, hard disk, and you have a lot of system lockups (hangs, crashes)crashes)

• you may think that the crashes are causing the file system errorsyou may think that the crashes are causing the file system errors• it is possible for the file system errors to cause the lockupsit is possible for the file system errors to cause the lockups• it is also possible that both are just symptoms of another it is also possible that both are just symptoms of another

underlying causeunderlying cause

Scan For File System ProblemsScan For File System Problems• If the problem you are looking at is anything that involves the If the problem you are looking at is anything that involves the

hard disk, files, operating system problems, crashes or similar hard disk, files, operating system problems, crashes or similar behavior, behavior, scan the file system for errorsscan the file system for errors

Use Diagnostic ToolsUse Diagnostic Tools

Correlation May Not Imply CausationCorrelation May Not Imply Causation• two strange things happening at the same time on your PC, two strange things happening at the same time on your PC,

does not mean that one of them has caused the otherdoes not mean that one of them has caused the other

• Example: you have frequent file system corruption on your Example: you have frequent file system corruption on your hard disk, and you have a lot of system lockups (hangs, hard disk, and you have a lot of system lockups (hangs, crashes)crashes)

• you may think that the crashes are causing the file system errorsyou may think that the crashes are causing the file system errors• it is possible for the file system errors to cause the lockupsit is possible for the file system errors to cause the lockups• it is also possible that both are just symptoms of another it is also possible that both are just symptoms of another

underlying causeunderlying cause

Scan For File System ProblemsScan For File System Problems• If the problem you are looking at is anything that involves the If the problem you are looking at is anything that involves the

hard disk, files, operating system problems, crashes or similar hard disk, files, operating system problems, crashes or similar behavior, behavior, scan the file system for errorsscan the file system for errors

Use Diagnostic ToolsUse Diagnostic Tools


Diagnostic, Troubleshooting and Diagnostic, Troubleshooting and Repair ToolsRepair ToolsDiagnostic, Troubleshooting and Diagnostic, Troubleshooting and Repair ToolsRepair Tools Diagnostic SoftwareDiagnostic Software

• use of diagnostic software tools can save you a great deal of use of diagnostic software tools can save you a great deal of timetime

• often provide hints or at least valuable information about what often provide hints or at least valuable information about what is in the system and how it is workingis in the system and how it is working

• Power-On Self Test (POST):Power-On Self Test (POST): • it is it is built into your system BIOSbuilt into your system BIOS and it runs every time you start and it runs every time you start

up your PC automatically. up your PC automatically. • It is often the best indicator of system problems; make sure you It is often the best indicator of system problems; make sure you

pay attention to its audio and video messages. Don't disable its pay attention to its audio and video messages. Don't disable its error-reporting functions unless you really need to. error-reporting functions unless you really need to.

• MEM.EXE:MEM.EXE: • provides you with details about your memory configuration, as provides you with details about your memory configuration, as

well as what is currently using your memory. well as what is currently using your memory. • It is especially useful when run with the "/C" parameter (use the It is especially useful when run with the "/C" parameter (use the

"/P" parameter as well to make the output pause when it is "/P" parameter as well to make the output pause when it is scrolling). scrolling).

Diagnostic SoftwareDiagnostic Software• use of diagnostic software tools can save you a great deal of use of diagnostic software tools can save you a great deal of

timetime• often provide hints or at least valuable information about what often provide hints or at least valuable information about what

is in the system and how it is workingis in the system and how it is working• Power-On Self Test (POST):Power-On Self Test (POST):

• it is it is built into your system BIOSbuilt into your system BIOS and it runs every time you start and it runs every time you start up your PC automatically. up your PC automatically.

• It is often the best indicator of system problems; make sure you It is often the best indicator of system problems; make sure you pay attention to its audio and video messages. Don't disable its pay attention to its audio and video messages. Don't disable its error-reporting functions unless you really need to. error-reporting functions unless you really need to.

• MEM.EXE:MEM.EXE: • provides you with details about your memory configuration, as provides you with details about your memory configuration, as

well as what is currently using your memory. well as what is currently using your memory. • It is especially useful when run with the "/C" parameter (use the It is especially useful when run with the "/C" parameter (use the

"/P" parameter as well to make the output pause when it is "/P" parameter as well to make the output pause when it is scrolling). scrolling).


Diagnostic, Troubleshooting and Diagnostic, Troubleshooting and Repair ToolsRepair ToolsDiagnostic, Troubleshooting and Diagnostic, Troubleshooting and Repair ToolsRepair Tools

• Microsoft Diagnostics:Microsoft Diagnostics: • Better known as "Better known as "MSD.EXEMSD.EXE", ", • very useful for seeing what disks are in the system, how much memory very useful for seeing what disks are in the system, how much memory

is installed, and also for checking system resource usage such as LPT is installed, and also for checking system resource usage such as LPT ports and IRQs. ports and IRQs.

• It will show you what type of BIOS you are using and also what UART It will show you what type of BIOS you are using and also what UART chip you have in your serial ports. chip you have in your serial ports.

• The Windows 95 Device Manager:The Windows 95 Device Manager: • the most useful tool for identifying system configuration and resource the most useful tool for identifying system configuration and resource

usage information under Windows 95. usage information under Windows 95. • To access it, open the Control Panel and select the "System" icon. Then To access it, open the Control Panel and select the "System" icon. Then

select the "Device Manager" tab. You will see a graphical "tree" select the "Device Manager" tab. You will see a graphical "tree" structure showing you all of your PC hardware. If you select "Properties" structure showing you all of your PC hardware. If you select "Properties" while "Computer" (the top-level item) is selected, you will be able to see while "Computer" (the top-level item) is selected, you will be able to see all the IRQs, DMA channels and I/O addresses in use in your PC; all the IRQs, DMA channels and I/O addresses in use in your PC;

• very useful for resolving resource conflicts! The same "Properties" very useful for resolving resource conflicts! The same "Properties" button, pressed after selecting a specific hardware device, will show you button, pressed after selecting a specific hardware device, will show you driver information, resource settings for the hardware item chosen, and driver information, resource settings for the hardware item chosen, and much more. much more.

• Microsoft Diagnostics:Microsoft Diagnostics: • Better known as "Better known as "MSD.EXEMSD.EXE", ", • very useful for seeing what disks are in the system, how much memory very useful for seeing what disks are in the system, how much memory

is installed, and also for checking system resource usage such as LPT is installed, and also for checking system resource usage such as LPT ports and IRQs. ports and IRQs.

• It will show you what type of BIOS you are using and also what UART It will show you what type of BIOS you are using and also what UART chip you have in your serial ports. chip you have in your serial ports.

• The Windows 95 Device Manager:The Windows 95 Device Manager: • the most useful tool for identifying system configuration and resource the most useful tool for identifying system configuration and resource

usage information under Windows 95. usage information under Windows 95. • To access it, open the Control Panel and select the "System" icon. Then To access it, open the Control Panel and select the "System" icon. Then

select the "Device Manager" tab. You will see a graphical "tree" select the "Device Manager" tab. You will see a graphical "tree" structure showing you all of your PC hardware. If you select "Properties" structure showing you all of your PC hardware. If you select "Properties" while "Computer" (the top-level item) is selected, you will be able to see while "Computer" (the top-level item) is selected, you will be able to see all the IRQs, DMA channels and I/O addresses in use in your PC; all the IRQs, DMA channels and I/O addresses in use in your PC;

• very useful for resolving resource conflicts! The same "Properties" very useful for resolving resource conflicts! The same "Properties" button, pressed after selecting a specific hardware device, will show you button, pressed after selecting a specific hardware device, will show you driver information, resource settings for the hardware item chosen, and driver information, resource settings for the hardware item chosen, and much more. much more.



• Norton System Information:Norton System Information: • SI is similar to the Microsoft Diagnostics, only more detailed in SI is similar to the Microsoft Diagnostics, only more detailed in

its later versions. its later versions. • SI shows a great deal of information about what is in the PC, SI shows a great deal of information about what is in the PC,

going well beyond what MSD gives you, but really is still an going well beyond what MSD gives you, but really is still an information utility as opposed to a true diagnostic. This program information utility as opposed to a true diagnostic. This program is part of Symantec's Norton Utilities. is part of Symantec's Norton Utilities.

• Microsoft ScanDisk and Norton Disk Doctor:Microsoft ScanDisk and Norton Disk Doctor: • used to check for hard disk problems. This includes file system used to check for hard disk problems. This includes file system

corruption and hard disk read errors. They should be used when corruption and hard disk read errors. They should be used when hard disk problems are suspected. hard disk problems are suspected.

• Norton Diagnostics:Norton Diagnostics: • perform tests on the hardware to identify problems. perform tests on the hardware to identify problems. • It includes tests of the processor and motherboard and system It includes tests of the processor and motherboard and system

memory, and will identify some types of resource conflicts. memory, and will identify some types of resource conflicts. • In reality it is still quite limited in terms of the numbers of In reality it is still quite limited in terms of the numbers of

problems it will find. problems it will find.

• Norton System Information:Norton System Information: • SI is similar to the Microsoft Diagnostics, only more detailed in SI is similar to the Microsoft Diagnostics, only more detailed in

its later versions. its later versions. • SI shows a great deal of information about what is in the PC, SI shows a great deal of information about what is in the PC,

going well beyond what MSD gives you, but really is still an going well beyond what MSD gives you, but really is still an information utility as opposed to a true diagnostic. This program information utility as opposed to a true diagnostic. This program is part of Symantec's Norton Utilities. is part of Symantec's Norton Utilities.

• Microsoft ScanDisk and Norton Disk Doctor:Microsoft ScanDisk and Norton Disk Doctor: • used to check for hard disk problems. This includes file system used to check for hard disk problems. This includes file system

corruption and hard disk read errors. They should be used when corruption and hard disk read errors. They should be used when hard disk problems are suspected. hard disk problems are suspected.

• Norton Diagnostics:Norton Diagnostics: • perform tests on the hardware to identify problems. perform tests on the hardware to identify problems. • It includes tests of the processor and motherboard and system It includes tests of the processor and motherboard and system

memory, and will identify some types of resource conflicts. memory, and will identify some types of resource conflicts. • In reality it is still quite limited in terms of the numbers of In reality it is still quite limited in terms of the numbers of

problems it will find. problems it will find.



• QAPlus:QAPlus: • QAPlus from QAPlus from DiagSoftDiagSoft is a more advanced diagnostic suite that is a more advanced diagnostic suite that

comes in several flavors, depending on what you need to do and comes in several flavors, depending on what you need to do and how you want to do it. how you want to do it.

• a more expensive package but can give you much more detailed a more expensive package but can give you much more detailed information about your system and help identify problem information about your system and help identify problem situations as well. situations as well.

Diagnostic HardwareDiagnostic Hardware• there are available several pieces of hardware that can be there are available several pieces of hardware that can be

very helpful in troubleshooting some specific hardware very helpful in troubleshooting some specific hardware problems. problems.

• Loop-Back Plugs:Loop-Back Plugs: • These are small plugs that go onto the serial and parallel ports These are small plugs that go onto the serial and parallel ports

on your computer and connect the receive to transmit lines to on your computer and connect the receive to transmit lines to simulate a connection (they connect the port to itself). simulate a connection (they connect the port to itself).

• Using these with a program like Norton Diagnostics allows for Using these with a program like Norton Diagnostics allows for full testing of the operation of these ports, whereas without them full testing of the operation of these ports, whereas without them only the internal portions of the port can be tested. only the internal portions of the port can be tested.

• QAPlus:QAPlus: • QAPlus from QAPlus from DiagSoftDiagSoft is a more advanced diagnostic suite that is a more advanced diagnostic suite that

comes in several flavors, depending on what you need to do and comes in several flavors, depending on what you need to do and how you want to do it. how you want to do it.

• a more expensive package but can give you much more detailed a more expensive package but can give you much more detailed information about your system and help identify problem information about your system and help identify problem situations as well. situations as well.

Diagnostic HardwareDiagnostic Hardware• there are available several pieces of hardware that can be there are available several pieces of hardware that can be

very helpful in troubleshooting some specific hardware very helpful in troubleshooting some specific hardware problems. problems.

• Loop-Back Plugs:Loop-Back Plugs: • These are small plugs that go onto the serial and parallel ports These are small plugs that go onto the serial and parallel ports

on your computer and connect the receive to transmit lines to on your computer and connect the receive to transmit lines to simulate a connection (they connect the port to itself). simulate a connection (they connect the port to itself).

• Using these with a program like Norton Diagnostics allows for Using these with a program like Norton Diagnostics allows for full testing of the operation of these ports, whereas without them full testing of the operation of these ports, whereas without them only the internal portions of the port can be tested. only the internal portions of the port can be tested.



• Multimeter/Ohmmeter:Multimeter/Ohmmeter: • An ohmmeter is a device that measures electrical resistance;An ohmmeter is a device that measures electrical resistance;• a multimeter can measure resistance, voltage and current. a multimeter can measure resistance, voltage and current. • A simple ohmmeter is useful primarily for checking for short A simple ohmmeter is useful primarily for checking for short

circuits or open circuits (broken connections, damaged cables, circuits or open circuits (broken connections, damaged cables, etc.) etc.)

• Multimeters can be used for more extensive electronics testing. Multimeters can be used for more extensive electronics testing.

• BIOS POST Cards:BIOS POST Cards: • It is well-known that the BIOS will, if it finds a problem during its It is well-known that the BIOS will, if it finds a problem during its

power-on self-test (POST), produce audio "beep codes" and/or power-on self-test (POST), produce audio "beep codes" and/or video messages that indicate what the trouble is that it found. video messages that indicate what the trouble is that it found.

• the BIOS of most PCs is designed to send a stream of test the BIOS of most PCs is designed to send a stream of test codes to a special memory location as it performs its tests, codes to a special memory location as it performs its tests, usually 80h. usually 80h.

• By using a special card designed to capture and display these By using a special card designed to capture and display these codes, you can pinpoint exactly where in the power-on self-test codes, you can pinpoint exactly where in the power-on self-test a system is hanging up. This can be extremely helpful in a system is hanging up. This can be extremely helpful in debugging very stubborn systemsdebugging very stubborn systems

• Multimeter/Ohmmeter:Multimeter/Ohmmeter: • An ohmmeter is a device that measures electrical resistance;An ohmmeter is a device that measures electrical resistance;• a multimeter can measure resistance, voltage and current. a multimeter can measure resistance, voltage and current. • A simple ohmmeter is useful primarily for checking for short A simple ohmmeter is useful primarily for checking for short

circuits or open circuits (broken connections, damaged cables, circuits or open circuits (broken connections, damaged cables, etc.) etc.)

• Multimeters can be used for more extensive electronics testing. Multimeters can be used for more extensive electronics testing.

• BIOS POST Cards:BIOS POST Cards: • It is well-known that the BIOS will, if it finds a problem during its It is well-known that the BIOS will, if it finds a problem during its

power-on self-test (POST), produce audio "beep codes" and/or power-on self-test (POST), produce audio "beep codes" and/or video messages that indicate what the trouble is that it found. video messages that indicate what the trouble is that it found.

• the BIOS of most PCs is designed to send a stream of test the BIOS of most PCs is designed to send a stream of test codes to a special memory location as it performs its tests, codes to a special memory location as it performs its tests, usually 80h. usually 80h.

• By using a special card designed to capture and display these By using a special card designed to capture and display these codes, you can pinpoint exactly where in the power-on self-test codes, you can pinpoint exactly where in the power-on self-test a system is hanging up. This can be extremely helpful in a system is hanging up. This can be extremely helpful in debugging very stubborn systemsdebugging very stubborn systems



• Test Bed:Test Bed: • Some experienced PC repair people keep around an older Some experienced PC repair people keep around an older

system that they can use as a test bed for components.system that they can use as a test bed for components.• It can be very useful to be able to test an unknown device with It can be very useful to be able to test an unknown device with

other components that are known to work, to cut down on the other components that are known to work, to cut down on the guesswork. guesswork.

To do any reasonable amount of work upgrading, To do any reasonable amount of work upgrading, building, troubleshooting or repairing PCs, a proper building, troubleshooting or repairing PCs, a proper tool kit is a good investmenttool kit is a good investment

PC ToolkitPC Toolkit• A Good ScrewdriverA Good Screwdriver: a good screwdriver with magnetic, : a good screwdriver with magnetic,

interchangeable bits and a comfortable handleinterchangeable bits and a comfortable handle

• Additional Screwdrivers:Additional Screwdrivers: An additional Philips An additional Philips screwdriver and an additional flat blade screwdriverscrewdriver and an additional flat blade screwdriver

• Test Bed:Test Bed: • Some experienced PC repair people keep around an older Some experienced PC repair people keep around an older

system that they can use as a test bed for components.system that they can use as a test bed for components.• It can be very useful to be able to test an unknown device with It can be very useful to be able to test an unknown device with

other components that are known to work, to cut down on the other components that are known to work, to cut down on the guesswork. guesswork.

To do any reasonable amount of work upgrading, To do any reasonable amount of work upgrading, building, troubleshooting or repairing PCs, a proper building, troubleshooting or repairing PCs, a proper tool kit is a good investmenttool kit is a good investment

PC ToolkitPC Toolkit• A Good ScrewdriverA Good Screwdriver: a good screwdriver with magnetic, : a good screwdriver with magnetic,

interchangeable bits and a comfortable handleinterchangeable bits and a comfortable handle

• Additional Screwdrivers:Additional Screwdrivers: An additional Philips An additional Philips screwdriver and an additional flat blade screwdriverscrewdriver and an additional flat blade screwdriver



• Needle-Nose Pliers:Needle-Nose Pliers: These are useful for grasping small These are useful for grasping small items and for removing and replacing jumpers on circuit items and for removing and replacing jumpers on circuit boards. boards.

• Wire Snips:Wire Snips: A pair of wire snips for cutting wire and stripping A pair of wire snips for cutting wire and stripping insulation. Some kits include wire strippers for the latter insulation. Some kits include wire strippers for the latter purpose. purpose.

• A Small Flashlight:A Small Flashlight: VeryVery useful; the insides of PC boxes are useful; the insides of PC boxes are quite dark and there are lots of very small things you will need quite dark and there are lots of very small things you will need to see, such as the "pin 1" marking on a connector for to see, such as the "pin 1" marking on a connector for exampleexample

• A Roll of Black Electrical Tape:A Roll of Black Electrical Tape: They never include this in They never include this in the kits but they should. Used for wrapping wire ends and the kits but they should. Used for wrapping wire ends and insulating components. insulating components.

• A Can of Compressed Air:A Can of Compressed Air: Very handy for cleaning things Very handy for cleaning things hands-free and without using any hazardous liquids. hands-free and without using any hazardous liquids.

• A Soft, Lint-Free Cloth:A Soft, Lint-Free Cloth: For cleaning the monitor and other For cleaning the monitor and other components. components.

• Needle-Nose Pliers:Needle-Nose Pliers: These are useful for grasping small These are useful for grasping small items and for removing and replacing jumpers on circuit items and for removing and replacing jumpers on circuit boards. boards.

• Wire Snips:Wire Snips: A pair of wire snips for cutting wire and stripping A pair of wire snips for cutting wire and stripping insulation. Some kits include wire strippers for the latter insulation. Some kits include wire strippers for the latter purpose. purpose.

• A Small Flashlight:A Small Flashlight: VeryVery useful; the insides of PC boxes are useful; the insides of PC boxes are quite dark and there are lots of very small things you will need quite dark and there are lots of very small things you will need to see, such as the "pin 1" marking on a connector for to see, such as the "pin 1" marking on a connector for exampleexample

• A Roll of Black Electrical Tape:A Roll of Black Electrical Tape: They never include this in They never include this in the kits but they should. Used for wrapping wire ends and the kits but they should. Used for wrapping wire ends and insulating components. insulating components.

• A Can of Compressed Air:A Can of Compressed Air: Very handy for cleaning things Very handy for cleaning things hands-free and without using any hazardous liquids. hands-free and without using any hazardous liquids.

• A Soft, Lint-Free Cloth:A Soft, Lint-Free Cloth: For cleaning the monitor and other For cleaning the monitor and other components. components.



• A 3/16" Nut Driver:A 3/16" Nut Driver: 3/16" is the size of nut most commonly 3/16" is the size of nut most commonly used on PCs. These hexagonal nuts are used as mounting used on PCs. These hexagonal nuts are used as mounting hardware for motherboards and serial and parallel ports. hardware for motherboards and serial and parallel ports.

• Vice Grips:Vice Grips: These are incredibly neat tools that have all sorts These are incredibly neat tools that have all sorts of uses. of uses.

• Torx Screwdrivers or Bits:Torx Screwdrivers or Bits: These are the star-shaped These are the star-shaped screwdriver heads that are used to make equipment "tamper-screwdriver heads that are used to make equipment "tamper-proof". proof".

• An ESD (Electrostatic Discharge) Wrist Strap:An ESD (Electrostatic Discharge) Wrist Strap: This is more This is more of a safety device than a tool; it is used to greatly reduce the of a safety device than a tool; it is used to greatly reduce the chances of static damage to components. chances of static damage to components.

• A Knife:A Knife: A cutting blade or utility knife of some sort. A cutting blade or utility knife of some sort.

• Soldering Irons:Soldering Irons: Essential if you are going to try to do repair Essential if you are going to try to do repair of circuit boards, but virtually nobody does this (and with good of circuit boards, but virtually nobody does this (and with good reason). They are also quite dangerous if used improperly. reason). They are also quite dangerous if used improperly.

• A 3/16" Nut Driver:A 3/16" Nut Driver: 3/16" is the size of nut most commonly 3/16" is the size of nut most commonly used on PCs. These hexagonal nuts are used as mounting used on PCs. These hexagonal nuts are used as mounting hardware for motherboards and serial and parallel ports. hardware for motherboards and serial and parallel ports.

• Vice Grips:Vice Grips: These are incredibly neat tools that have all sorts These are incredibly neat tools that have all sorts of uses. of uses.

• Torx Screwdrivers or Bits:Torx Screwdrivers or Bits: These are the star-shaped These are the star-shaped screwdriver heads that are used to make equipment "tamper-screwdriver heads that are used to make equipment "tamper-proof". proof".

• An ESD (Electrostatic Discharge) Wrist Strap:An ESD (Electrostatic Discharge) Wrist Strap: This is more This is more of a safety device than a tool; it is used to greatly reduce the of a safety device than a tool; it is used to greatly reduce the chances of static damage to components. chances of static damage to components.

• A Knife:A Knife: A cutting blade or utility knife of some sort. A cutting blade or utility knife of some sort.

• Soldering Irons:Soldering Irons: Essential if you are going to try to do repair Essential if you are going to try to do repair of circuit boards, but virtually nobody does this (and with good of circuit boards, but virtually nobody does this (and with good reason). They are also quite dangerous if used improperly. reason). They are also quite dangerous if used improperly.



• Hex (Allen) Keys:Hex (Allen) Keys: included in virtually every commercial tool included in virtually every commercial tool kit but rarely used.kit but rarely used.

• Chip Extractors:Chip Extractors: These are used to remove chips from These are used to remove chips from regular (non-ZIF) sockets, but modern PCs do not generally regular (non-ZIF) sockets, but modern PCs do not generally use these sockets any more. use these sockets any more.

• Screws:Screws: screws of all shapes and sizes come in handy when screws of all shapes and sizes come in handy when working on various machines. working on various machines.

• Mounting Kits:Mounting Kits: These sometimes come with retail hard disks These sometimes come with retail hard disks and allow you to put a 3.5" drive into a 5.25" bay. Useful and allow you to put a 3.5" drive into a 5.25" bay. Useful when your case has more free 5.25" bays than 3.5" ones. when your case has more free 5.25" bays than 3.5" ones.

• Cables:Cables: Save any power, IDE, floppy, CD-ROM, or other Save any power, IDE, floppy, CD-ROM, or other cables that you accumulate in case you need them later on. cables that you accumulate in case you need them later on.

• Keyboard, Mouse, 3.5" Floppy Drive:Keyboard, Mouse, 3.5" Floppy Drive: Keep an extra one of Keep an extra one of each of these components around to aid in troubleshooting each of these components around to aid in troubleshooting problems by swapping. problems by swapping.

• Hex (Allen) Keys:Hex (Allen) Keys: included in virtually every commercial tool included in virtually every commercial tool kit but rarely used.kit but rarely used.

• Chip Extractors:Chip Extractors: These are used to remove chips from These are used to remove chips from regular (non-ZIF) sockets, but modern PCs do not generally regular (non-ZIF) sockets, but modern PCs do not generally use these sockets any more. use these sockets any more.

• Screws:Screws: screws of all shapes and sizes come in handy when screws of all shapes and sizes come in handy when working on various machines. working on various machines.

• Mounting Kits:Mounting Kits: These sometimes come with retail hard disks These sometimes come with retail hard disks and allow you to put a 3.5" drive into a 5.25" bay. Useful and allow you to put a 3.5" drive into a 5.25" bay. Useful when your case has more free 5.25" bays than 3.5" ones. when your case has more free 5.25" bays than 3.5" ones.

• Cables:Cables: Save any power, IDE, floppy, CD-ROM, or other Save any power, IDE, floppy, CD-ROM, or other cables that you accumulate in case you need them later on. cables that you accumulate in case you need them later on.

• Keyboard, Mouse, 3.5" Floppy Drive:Keyboard, Mouse, 3.5" Floppy Drive: Keep an extra one of Keep an extra one of each of these components around to aid in troubleshooting each of these components around to aid in troubleshooting problems by swapping. problems by swapping.


Troubleshooting FlowchartsTroubleshooting FlowchartsTroubleshooting FlowchartsTroubleshooting Flowcharts

Power SupplyPower Supply• check Power Good pin for 2.4 to 5.4 dccheck Power Good pin for 2.4 to 5.4 dc

• measure voltage ranges on motherboard and drive power measure voltage ranges on motherboard and drive power connectorsconnectors

System BoardSystem Board• check all power connectorscheck all power connectors

• make sure board is cleanmake sure board is clean

• check all system-board switch settingscheck all system-board switch settings

• check resistance values at motherboard power connectorscheck resistance values at motherboard power connectors

• run advanced diagnostics - 1xxrun advanced diagnostics - 1xx

Power SupplyPower Supply• check Power Good pin for 2.4 to 5.4 dccheck Power Good pin for 2.4 to 5.4 dc

• measure voltage ranges on motherboard and drive power measure voltage ranges on motherboard and drive power connectorsconnectors

System BoardSystem Board• check all power connectorscheck all power connectors

• make sure board is cleanmake sure board is clean

• check all system-board switch settingscheck all system-board switch settings

• check resistance values at motherboard power connectorscheck resistance values at motherboard power connectors

• run advanced diagnostics - 1xxrun advanced diagnostics - 1xx



Video Board/AdapterVideo Board/Adapter• problem indicated by one long and two short beepsproblem indicated by one long and two short beeps

• run advanced diagnostics - 4xx and 5xxrun advanced diagnostics - 4xx and 5xx

KeyboardKeyboard• cable defective or stuck keycable defective or stuck key

• observe POST for 3xx errorobserve POST for 3xx error

• 3xx preceded by two-digit hexadecimal number, indicates 3xx preceded by two-digit hexadecimal number, indicates failing keyfailing key

• check voltages at system-board keyboard connectorcheck voltages at system-board keyboard connector

Video Board/AdapterVideo Board/Adapter• problem indicated by one long and two short beepsproblem indicated by one long and two short beeps

• run advanced diagnostics - 4xx and 5xxrun advanced diagnostics - 4xx and 5xx

KeyboardKeyboard• cable defective or stuck keycable defective or stuck key

• observe POST for 3xx errorobserve POST for 3xx error

• 3xx preceded by two-digit hexadecimal number, indicates 3xx preceded by two-digit hexadecimal number, indicates failing keyfailing key

• check voltages at system-board keyboard connectorcheck voltages at system-board keyboard connector



BatteryBattery• defective if error 161 by POSTdefective if error 161 by POST

• system unable to maintain date and time with power offsystem unable to maintain date and time with power off

Fixed Disk DriveFixed Disk Drive• problems indicated by 17xx errorsproblems indicated by 17xx errors

• check for proper configurationcheck for proper configuration

• check cables and measure voltagescheck cables and measure voltages

• attempt low level formatattempt low level format

Floppy DriveFloppy Drive• problems indicated by 6xx errorsproblems indicated by 6xx errors


BatteryBattery• defective if error 161 by POSTdefective if error 161 by POST

• system unable to maintain date and time with power offsystem unable to maintain date and time with power off

Fixed Disk DriveFixed Disk Drive• problems indicated by 17xx errorsproblems indicated by 17xx errors


• check cables and measure voltagescheck cables and measure voltages

• attempt low level formatattempt low level format

Floppy DriveFloppy Drive• problems indicated by 6xx errorsproblems indicated by 6xx errors




Serial and Parallel PortsSerial and Parallel Ports• run advanced diagnostics communicationsrun advanced diagnostics communications

• 9xx and 10xx for Parallel printer adapter9xx and 10xx for Parallel printer adapter

• 11xx for serial port COM111xx for serial port COM1

• 12xx for COM2, COM3, and COM412xx for COM2, COM3, and COM4

Serial and Parallel PortsSerial and Parallel Ports• run advanced diagnostics communicationsrun advanced diagnostics communications

• 9xx and 10xx for Parallel printer adapter9xx and 10xx for Parallel printer adapter

• 11xx for serial port COM111xx for serial port COM1

• 12xx for COM2, COM3, and COM412xx for COM2, COM3, and COM4


SummarySummarySummarySummary


Knowing how operating system boots helps Knowing how operating system boots helps pinpointing problempinpointing problem

Check installation and configurationCheck installation and configuration Start with items most likely to cause problemStart with items most likely to cause problem Check environmentCheck environment Get help of diagnostic toolsGet help of diagnostic tools Keep system documentation and manuals nearbyKeep system documentation and manuals nearby


Knowing how operating system boots helps Knowing how operating system boots helps pinpointing problempinpointing problem

Check installation and configurationCheck installation and configuration Start with items most likely to cause problemStart with items most likely to cause problem Check environmentCheck environment Get help of diagnostic toolsGet help of diagnostic tools Keep system documentation and manuals nearbyKeep system documentation and manuals nearby

troubleshooting guide dr. aiman h. el-maleh computer engineering department dr. aiman h. el-maleh...

Documents

possible n

time n

stubborn n

os loadsstarts n hardware

open mind n

wary of fatigue n

problem n dont jump

advantage of warranty