These notes were written in 1996 and haven't been updated yet so please understand some details are out of date, I will be updating the notes in the near future
INTRODUCTION TO
COMPUTER MAINTENANCE - COURSE OUTLINE
Introduction
DOS & Windows
Safety
Hardware & Software
General PC Layout
Identifying Components
The Hard drive
Setting 1 & 2 drives up in a system
Different types of drives
Building a PC
Fault Finding & Trouble Shooting
Common problems & Fixes
Copyright 1996 Keith Nolan - No part of these notes may be reproduced without written consent
MODULE 1
DOS & Windows
Many people think Dos is gone with the advent of windows 95 but Dos is a must to know
if you are involved in computer maintenance Dos stands for disk operating system. Dos is the most common operating system in PC`S. I would advise anyone that does not have a working knowledge of dos to attend our CLASS
INTRODUCTION TO COMPUTERS (This class gives a good knowledge of dos , windows &
Windows 95 The following is the least you need to know
6. Some programs need parameters after them e.g. c:\dos\xcopy *.* c:\temp /s/e/v
(the /s/e/v are the parameters they tell the command what to do i.e. in this case copy
subdirectories , empty directories and verify the copy). Usually to get a list of
Parameters type the command followed by a /?. 7. With Dos v6 you can type help and press Enter to get a list of
commands and what they do. 8. Dos commands that you can run have the following extensions - .com .exe .bat (.bat
files are text files that run a number of commands(exe,com)) Now that we have covered the basics of dos lets start with windows Windows is a program just like any other, to enter windows you change to the windows
directory and type the command to start it so type cd \windows and press Enter
then type win and press Enter. Now when you enter windows you have a very different screen (see the diag with
explanations of the screen) The following is the least you need to know (but as with dos if you do not know windows
I would advise the introduction to computers course)
Safety
Before you start poking around inside a computer there are some safety precautions you should be aware of
Hardware & Software
Hardware is anything you can touch in a computer e.g. The hard disk, the floppy drive, the mother board etc. Software is what makes the computer so handy because it tells the computer what to do, it is also where most of the problems occur examples of software DOS (This is a very important part of software without it or some other operating system the computer will do nothing) , Applications e.g. Word a word processor , Commands e.g. format these are (usually part of Dos)
MODULE 2
Identifying Components
The Motherboard
The motherboard , as the name implies, is the main circuit board in the computer into which any other circuit boards slot. These other circuit boards include expansion cards and memory boards. These expansion slot are called the data BUS. There are a number of different bus types they are ISA(industry standard architecture) , VESA(video electronic standards association) , PCI(peripheral component interconnect) , EISA(extended industry standard architecture) AND MCA(micro channel artitecture). The motherboard also contains the Central Processor Unit or CPU.
The Central Processor Unit or CPU
The "heart" of the PC is a microprocessor chip created by Intel corporation or some other company licensed by Intel. Intel has designed and created many microprocessors over the years, but the ones that interest us are the 8088 ,80286 , 80386 , 80486 , and the Pentium, as well as the not yet released P6.
CPU performance determines, in part , computer performance. CPUs vary in several ways that affect their performance. These variations are shown below .
Memory
On a modern motherboard this normally takes the form of SIMM’s (Single In-line Memory Modules) . The two different types of SIMM’s you will encounter are 30-pin and 72-pin. The newer motherboards will only take 72-pin memory .
The different types of 72-pin SIMMs
EDO (or Extended Data Out) SIMM’s do increase the efficiency of the motherboard as long as it has been designed to take them. A motherboard designed for EDO SIMM’s can use the standard ones - you will just not get the increased efficiency.
Parity Memory - Parity checking is a means by which memory can be tested for errors. Parity SIMM’s may be used in non-parity systems. The system will simply ignore the extra bits - you will just have used more expensive memory than you needed to. If you use non-parity SIMM’s in a system requiring parity SIMM’s and where parity is enabled, you will instantly get memory errors
Floppy drive(s)
Mostly nowadays PC’s come fitted with 3.5"HD (High-density) 1.44Mb floppy drives. Today’s programs are large and it is no longer realistic to fit low-density drives. If you still have a lot of software on 5.25" disk or have another reason, then you may wish to fit one of these drives as well - but they are now obsolete.
The display system (Video cards)
There are a huge variety of display cards available. Like everything else in computing the specifications are getting higher all the time. Windows is now the most popular environment used on the PC. As this is a graphical environment it places much greater demands on the display adapter than DOS applications which are basically text. Even the graphics in DOS are made up of text and text symbols and screen fills and are therefore there is a relatively small amount of information to be processed. In Windows however there are very large amounts of information being processed all the time. The graphics can be complicated, at a very high resolution, be in "true" colour (16.8 million colours) and be updated very fast.
The display card needs to be chosen in conjunction with the type of monitor and motherboard you have. Indeed the display adapter may be an integral part of the motherboard. This is more common on "name brand" PCs. The common type of display card nowadays is a SVGA card - This card will give very high quality output (depending on the amount of memory on the card)
The I/O card or circuitry (Controller card)
As with the display adapter this can also be an integral part of the motherboard or on a separate expansion card. I/O stands for In/Out and is for connecting devices that are either sending information to (In) or getting information from (Out) the computer. Disk drive controllers used to come on separate cards. If you need an I/O card then the simplest solution nowadays is a Multi I/O card, which combines the disk drive controllers along with your serial and parallel ports and perhaps a game port all onto one card. However most motherboards now come with built-in I/O circuitry and the ports connect via ribbon data cables.
MODULE 3
THE HARD DISK
The hard disk can be counted as the most important part of a computer as this is where all the information \ Data is stored
There are a number of types. IDE (Integrated Drive Electronics) was until recently the most popular and cost-effective choice. EIDE (Enhanced) is fast taking its place as prices fall. SCSI (Small Computer System Interface) is a more expensive choice and not so common unless you want a particularly large disk, where they become more cost effective, or you already have a SCSI system and wish to extend it.
EIDE
Enhanced Integrated Drive Electronics (EIDE) or ATA-2 is a modification to the original IDE or ATA (Advanced Technology Attachment) specification. It is often called Extended IDE and features improvements in the Identify Drive command which allows a new drive to describe its own characteristics to the software, thus facilitating Plug and Play (PnP). EIDE have improved on the original IDE standard in four ways: Allowing larger drive sizes, faster transfer of data, a secondary two-device channel, and ATA Packet Interface(or ATAPI).
STEPS INVOLVED IN SETTING UP A (SECOND) IDE/EDIE HARD DRIVE
1. Physically install the hard drive
2. Select the master / slave jumper depending on whether it is a single (master) or second drive (slave)
3. Connect the IDE cable (making sure the red line is towards pin 1) and the power cable
4. Setup the drive in the CMOS (Cylinders , Heads , and Sectors)
5. Using a boot disk - boot the system and run a command called FDISK (as shown in class)
6. In Fdisk do the following
a) Create a primary Dos partition
b) Set this partition active (only for the boot drive)
c) Exit Fdisk
7. Now format the new drive by typing Format C: /S or for a second drive Format D:
8. The new drive can now be accessed to install Dos or what ever software you want on it
Setting up a drive in the BIOS
When you are setting up a Hard drive in the CMOS there are a few things you need to know
1. The number of Cylinders (Explained below)
2 The Number of Heads
3. The number of Sectors
This information is hopefully written on the drive if it is not use the utility supplied (IDEID) to find the settings - With all modern Bios there is a auto detect option if it is there take it. If the machine is pre 1992 then the Bios does not more than likely support EIDE drives i.e. drives with more than - 64 sectors - 64 heads - 1024 cylinders and above (usually more than 528MB drives are EIDE )
Disk Geometry: Heads, Tracks , Cylinders , and Sectors
If I wanted to tell you how to get to my house , then I might say something like "Travel South towards Ballincollig , then take the first left after the village , pass the two estates , take the next right ---etc..." In order to understand what I’m talking about, you’d have to understand south ,left , right , and estate. In the same way you can’t even think about doing disk work without understanding terms like Cylinder , Head , Sector , and Track - words that are just as basic to disk discussions.
Data is stored on disks in bytes. The bytes are organized into 512 - byte groups called sectors , and sectors are the minimum unit of data that you can read from or write to a disk. Sectors are grouped into tracks, tracks are sometimes conveniently arranged into groups called cylinders. A disk has at least two surfaces.
Disk Heads
A hard disk has an electromagnetic read/write head for each side of each surface. For example on the original XT 10MB drive, there were fours heads; two heads/surface * two surfaces.
Disk Tracks
Each side of each surface(sometimes called a platter) is divided into contric tracks , like a floppy. A floppy like the 360K has 40 tracks, but hard disks start at 305 tracks and go up from there.
Cylinders
On a hard disk, there is usually more than on platter, so most hard disks have four or more read/write heads. All of a disk’s heads - whether they are the two heads a floppy has or the 16 found on some drives - are attached to a bracket called an actuator arm. That means that when head 0 is positioned over track 142 on surface 0 by the head actuator, head 3 is also positioned over track 142 on surface 3. Disk heads cannot be independently positioned, and that leads us to the notion of a cylinder
To read a particular sector, the disk hardware goes through two steps. First, it must move the read/write head over the desired track. Second , it must wait for the disk to rotate so that the desired sector is under the head, and lastly, read. In general, moving the head takes the most time. This means that we’d most quickly read a file whose sectors were all on the same track, and whose tracks lay above one another--- one head move reads a pile of data. Thus, if a large file starts out on say, head 0, track 271, then it’s a good idea to make sure that the next track that the file uses is head 1 , track 271, and then head 2 , track 271 , and so on; there’s no need for a head movement, but the disk can suck up a lot of data.
There is, then , a relationship between all of the tracks labeled 271 in this example. That’s called a cylinder. The number of tracks per surface is identical to the number of cylinders
Sectors
Each surface is then divided into tracks, which are divided into sectors
so to get the size of the drive you have -- heads * tracks(cylinders) * sectors * 0.5K (On each sector) = Size of the drive
e.g. A 10MB XT hard disk has
4 Surfaces
305 tracks on each surface
17 sectors on a track
0.5 K on each sector
so 4*305*17*0.5K=10,370K bytes = 10 MB
MODULE 4
BUILDING A PC
There are many things you have to take into account when building a PC.Other items you need
For a multimedia machine you also need
For the Internet
1. A modem (28.8 modem if possible)
That’s about all you need to build the hardware side of a PC.
Once the Hardware is put together you then need to add software
this includes your operating system and any applications
ADDING EXTRA CARDS TO THE COMPUTER
GENERAL
Physically building the computer is easy now that they are a modular design. The mental problem really is to get the components happily talking to each other. If computer builders and upgraders get in a muddle then this is where it usually happens. And yet it need not be complicated if you take a logical approach.
WINDOWS 95 AND "PLUG AND PLAY"
In order to get around this problem Microsoft have included "Plug and Play" into their new operating system. This means that you merely plug in the expansion cards and the computer will configure them for you. This sound great but I must point out that this only works if you have "Plug and Play" hardware. At the moment the majority of hardware is still not. Ultimately "Plug and Play" should make configuration problems a thing of the past (in theory at least!). In the meantime I thing it would still be wise to read on.
TECHNICAL OR NOT?
Now I can go into a long technical explanation of how IRQ`s are Interrupt requests, DMA`s are Direct Memory Access channels etc. and what they all do and so forth. If you are very technically minded maybe that is what you want. But I find that most people really just want to know "how do they affect me when I am upgrading and how can I avoid problems?".
The important thing to remember is that all these settings must be unique. They are addressing the computers resources in a certain place and if something else tries to access this place at the same time there will be a clash! This may result in one of the devices not being recognized by the system or in a system hanging or crashing. It is made worse as not all clashes show up straight away. They will wait until a particular combination of devices is used simultaneously. You may even put this crash down to something else.
CMOS SETTINGS
CMOS stands for Complementary Metal Oxide Semiconductor although you do not need to remember this. It is also known as your BIOS chip and this stands for Basic In Out System. And this is what it does. It handles the basic way data flows into and out of your computer.
Usually when people refer to bios they refer to those settings which cannot be changed and when they refer to CMOS they refer to the settings that can be changed in the setup (BIOS utility) program.
The user definable information about your system includes how many floppy drives and hard disks the system has and what type. It also contains information about the video display and how certain areas of memory are mapped. This information is programmed from your setup program, which is a program, which you run when you first start up a newly built PC or after certain upgrades. There is a small system rechargeable battery, which supplies the CMOS chip with power to retain this information. If this battery runs out (which only happens occasionally if the battery is old or faulty or rarely used) you will lose all this system information and will not be able to use your computer without it. You will need to run the setup program again (after maybe replacing the battery) before you can boot your PC. Some of the information maybe obvious to you like how many floppy drives you have. Some of the information will not be so obvious. Such as the Hard disk settings. The settings for these are sometimes found written on the drive itself or you may be lucky to have an auto detect feature in the CMOS(most 486 and newer PC`S do). It is important to get this information right as you could not start the system and you might even damage you hard drive.
FURTHER INFORMATION
For those of you who require a bit more information about IRQ’s etc. Read this.
But those who just wish to know "how" but not "why may skip it
IRQ’S
IRQ’s are interrupt request’s or vectors. Sometimes just called interrupts.
Interrupts are a method used by the computer for devices to get processors attention.
It is a bit like a shop system where you take a numbered ticket and you get served when your number is called. When a device needs the processors attention, it sends out an interrupt request signal which is noted by the processor which will "serve" it when its turn comes. If two devices share the same IRQ, the processor will attempt to handle them both at the same time and this is what causes problems.
DMA’S
DMA’s are direct memory access channels, which allow direct access to the systems RAM without going through the systems processor. This has two advantages, one is that this type of memory is faster, the other is that the processor is free to do something else. These channels must be allocated uniquely.
MEMORY ADDRESSES
Memory addresses are specific areas of memory ( just as postal addresses refers to a specific place), which are reserved for special use. Memory addresses are counted in hexadecimal notation ( to base 16). This type of counting the digits 0 two 9 for the first 10 and then the letters A to F to take us up to 16. The first megabyte of your systems memory occupies a range from 0000 to FFFF. You need not learn to count in hexadecimal as it is only necessary to insure that there are no conflicts.
BOOTING
You will find the term "booting" your computer frequently used throughout computer documentation. The term comes from the phrase "Pulling oneself up by ones bootstraps" This analogy comes about as when a computer is off it knows nothing. Its main memory is empty. The only thing the computer has to start with is a little bit of information stored in the BIOS (Basic in out system) chip on the motherboard (also known as the CMOS chip)
BIOS is not enough for the computer to run on alone but it initiates the boot cycle. First it runs POST (Power on self-test) which does some basic tests on the system. If the computer passes this test BIOS tells it to look for an operating system on a disk drive. If there is a disk in the floppy drive it will look at it first. If this is not a system disk you will see an error "Non system disk or disk error. Replace and strike any key when ready."
If there is no floppy in the drive then it will look for the hard disk, which has been nominated the boot disk. It will then load the operating system if all is well.
Sometimes all is not well though. If the CMOS settings have been lost because the battery has died. If the CMOS settings have been incorrectly set. If the hard drive is a new one and does not yet have an operating system on it. There are many reasons why this might happen
This is where booting from a system floppy disk is useful or even essential. A system disk has enough of the essential files of the operating system disk for the machine to run.(This will be covered in module 5 common problems & fixes)
MODULE 5
Fault finding.
General Troubleshooting Rules
1. Remember "Don’t Panic" and "I will win"
2. Write Everything Down
3. Do the easy stuff first
4. Reboot and try again
5. Simplify your configuration and reboot
6. Draw a picture
7. Separate the parts into components and test components
8. Never assume something is good
9. Trust no one: The documentation sometimes lies
Seven Steps to Troubleshooting Success
The smart trouble-shooter makes the troubleshooting job tractable by breaking down problems into steps. Don’t panic, and remember to be methodical; otherwise you will thrash helplessly about and get frustrated. Once you are frustrated, you are lost, and you start creating new problems.Following is the method that I use. It looks a lot like methods suggested by other people, but it’s not the only method. You certainly don’t have to use my method, but find one you like, and stick to it. Its the "this’ll only take five minutes" repairs that get me into trouble.
Before opening up the computer, do the following:
1. Check the NUT behind the keyboard.
2. Check that everything is plugged in: power , monitor , phone lines , printer , modem , and so on.
3. Check the software.
4. Ask: "What am I doing differently?" What’s new?
5. Check external signs. Make notes of them.
6. Run the diagnostics disk.
Only then , if you still haven’t solved the problem:7. Disassemble the machine, push the socketed chips back into their sockets, clean the connectors , and put the machine back together.
Notice that the first six steps aren’t hardware steps
Common Hardware Problems
Problem: Computer/Monitor/Other Mains operated equipment won’t start at all. No sign of life
Checks: Is it connected and turned on?
5. Possible power supply problem.
Problem: Hard disk drive doesn’t work or computer will no longer boot since I installed it/Them.
Problem : Floppy disk drive doesn’t work or computer will no longer boot since I installed it/them.
Problem: CD-ROM drive fitted does not work properly or at all.
5. Expansion cards
Problem : Any expansion card or peripheral device connected to one does not work properly or at all.
6. Corrupt data
Problem: I keep getting data on the hard disk going corrupt. I keep getting GPF`S (General Protection Faults) in windows. Directory entries keep going invalid. Even though I keep re-installing the software from the original installation disk these problems keep recurring.
These sort of recurring data integrity problems can have a number of possible causes. Try the following remedies.
7. Try the solutions in "Solving common software problems".
If you have run through all the possibilities you can think of after having considered the above and relevant documentation (don’t forget the readme files, which often contain last minute information) then you may decide it is time for the technical helpline. Before you ring a helpdesk have a clear mind of what you have done , what the problem is , and under what circumstances the problem happens. The following is a collection of the more common helpdesk numbers.
Solving Common Software problems.
The most common problem people have is that windows crashes.
There are a few things you can do to protect yourself from these crashes
If you run four or five Windows applications at the same time, If you haven’t upgrades your printer and video drivers for a couple of years, If you keep running out of memory (Hard disk space and RAM) Then you are a prime candidate for a windows crash. But there are things you can do - you won’t be able to get rid of windows crashes entirely but you can certainly make windows more stable.
General Protection Faults (GPF`s) are usually the problems behind a windows crash. GPF`s happen because windows is a Multi-tasking environment which means it tries to do several things at once (In theory anyway) But the best laid plans go wrong sometimes and you get a GPF. GPF`s happen when a program butts in on an area of memory needed by another piece of software(it could be an application, device driver or even windows itself)GPF`s can also be caused by a DOS application directly accessing a piece of hardware(the printer, for example)
Degrees of GPF`s
There are two types of GPF`s , both of which are deeply unpleasant and usually leave you with only one solution: to reboot the PC. If your machine just hangs, you have the option of pressing Ctrl+Alt+Del to get more information. If there’s a way out of the situation you’ll see the following message:
System has either become busy or has become unstable
-Press any key to return to windows and wait
- Press Ctrl+Alt+Del again to restart your computer
(all unsaved information will be lost)
It’s worth pressing a key and then waiting for windows to get its act together, although windows seldom recovers and then you’re forced to reboot in the end.
On the other hand, if you see this message, impending doom certainly awaits:
This Windows application has stopped responding to the system
-Press ESC to cancel and return to windows
-Press ENTER to close this application(all unsaved information will be lost)
-Press Ctrl+Alt+Del again to restart your computer(all unsaved information will be lost)
In this situation, It’s worth pressing the ESC key to see if you can get back to your application and quickly save your data. Pressing the ENTER key will allow you to close the offending application and return to windows. In both cases, once you’ve seen these messages and tried to save your data you should restart the PC as soon as possible.
Some GPF`s can be random curses sent to plague us. But more often than not it’s the same doggy device driver or half-installed application that’s causing the problem. The hard part is tracking down the culprit.
Hunting down GPF`s
Because we’re about to go tinkering with configuration files it’s worth making backups of the important files before we make any changes. Make copies of the - autoexec.bat , config.sys , win.ini and system.ini files. (Just in case anything goes wrong we can copy these back to their original directories)
Start by taking a close look at the GPF error message, which usually gives a few clues. Typically, the message tells you what program caused the GPF. This at least gives you somewhere to start.
Make sure you’re running applications designed for the version of windows you’re using ( Running applications designed for other versions of windows can cause GPF`s)
A common cause of GPF`s is a new upgrade - maybe you’ve added a new piece of software or installed a CD-ROM drive. If you’ve upgraded recently try deinstalling any new software or removing all mention of the new hardware drivers from your configuration files.
If this gets rid of your GPF`s call your supplier or manufacture of the software/hardware and find out if they have a solution.
If you’re running windows 3.1 (not windows for workgroups) you’ll find, hidden in your windows\system directory, a little diagnostic utility called Dr Watson. If you’re running a later version of windows then you can get hold of Dr Watson from the windows resource kit. Just load Dr Watson and when you next have a GPF , Dr watson creates a file in your windows directory called DRWATSON.LOG , which details exactly what was happening when windows crashed.
When the General Protection Fault dialogue box appears you’ll see an explanation , along with some data, which looks like gibberish but could help the application vendor track down exactly what’s causing the problem.
If your GPF keeps happening in the same program or driver, it’s worth reinstalling that piece of software. Perhaps the program files have got corrupted and reinstalling them from the original disks could solve the problem.
6. Clean up the hard disk
If the machine hangs mysteriously when you’re trying to access a file and you find you’re getting garbled output from your printer it’s worth cleaning your hard disk. Lost clusters or cross-linked files can cause crashes. To ward off trouble use DOS command CHKDSK regularly to nip any problems in the bud. To get CHKDSK to check drive C and to repair any problems it finds with files, use the following command, from the DOS prompt:
CHKDSK C: /F
Another tip is to run Chkdsk or SCANDISK as soon as you’ve rebooted your machine after having been hit with a GPF. GPF’s can leave the hard disk in a state of disarray and you’ll probably need to carry out a few minor repairs.
It’s also a good idea to keep a fair bit of free disk space. Windows programs can do funny things if they don’t keep at least 10Mb free, and make sure that the SET TEMP= line in the Autoexec.bat points to a valid path on this drive.
7 Get rid of WIN.INI
The GPFs might be down to corrupted fonts or printer drivers. Or they could be caused by software loading from the RUN= or LOAD= lines in your WIN.INI file that’s causing problems. The trick here is to quit windows and then rename the WIN.INI file by typing in the following at the dos prompt
REN C:\WINDOWS\WIN.INI WININI.OLD
Then load up windows. If this gets rid of your GPFs then rename WININI.OLD back to WIN.INI but take a look at the LOAD= and RUN= lines in the [windows] section of the file. To stop any software loading automatically, put a semicolon at the beginning of these two lines
8 Check the video drivers
Video drivers can often be troublemakers. Doggy video drivers can cause random GPFs, blank screens and mysterious crashes. To find out if your video driver is the root of the problem, first use Microsoft Diagnostics program (MSD) to find out what kind of video card you have, If MSD tells you that you have a video BIOS which dates back to before 1988 it’s worth calling the video card manufacturer to see if an updated BIOS is available.
The most common cause of GPFs is the video card driver, Check how old your driver is. Open up File Manager and find the windows\system directory. Then sort the files by extension order and look for DRV files. Here you should find the video driver files; select the driver file you a currently using and then press ALT+ENTER. This pops up a Properties dialog box, which includes information on version numbers
Call up the video card manufacturer and ask if this is the latest version of the driver. If it’s not, get them to sent you an updated driver.
9 If all else fails
As a last resort you should deinstall and reinstall Windows. Run Windows setup and choose the Custom setup option. Install Windows into a new subdirectory to make sure that the files are copied to a new location on the hard disk.
To get bare bones, GPF-free, Windows installation, go for the plain VGA display option and set the mouse option to "No mouse or pointer device", I n the windows setup dialog box also clear the setup printers check box and set up applications already on the hard disk check box and then choose OK. Let windows update you config.sys and autoexec.bat files. If the GPFs persist you’ve a problem with the hard ware or the BIOS.