Certification Objectives
 | Functions of System Modules |
| Adding and Removing Field Replaceable Modules |
| IRQs, DMAs, and I/O Addresses |
| Peripheral Ports, Cabling, and Connectors |
| Installing and Configuring IDE/EIDE Devices |
| Installing and Configuring SCSI Devices |
| Installing and Configuring Peripheral Devices |
| Functions and Use of Common Hand Tools |
| Upgrading BIOS |
| System Optimization |
Functions of System Modules
When you think of a computer, you generally picture a monitor and a keyboard hooked up to a box. However, there are many components, called Field Replaceable Modules (FRMs) orField Replaceable Units (FRUs), that make up a computer system. Each FRU has a specific function to perform, whether it accepts data from a user or produces data for a user. As a technician, you need to familiarize yourself with the various modules that are available on the market. The following subsections describe each FRU's function and explain the basic terms and concepts related to each module.System Board
The most important module of every computer system is the system board, also referred to as the main board, the motherboard, and the planar board. The system board is made from a fiberglass sheet interlaid with electronic circuitry. This circuitry provides the pathways for electrical signals, referred to as the bus, to travel across the board. Every module that makes up a computer system attaches to the motherboard and is able to communicate with other modules through the bus. Also found on the system board are the central processing unit (CPU), memory slots, cache, various connectors, and expansion slots.Expansion slots come in several varieties, and are labeled according to the type of bus architecture that is used. Examples of bus architecture are Industry Standard Architecture (ISA), Extended Industry Standard Architecture (EISA), Peripheral Component Interconnect (PCI), and Micro Channel Architecture (MCA), just to name a few. Each bus architecture is responsible for distributing signals back and forth from the expansion slot to the system board, and typically only one or two types are available on any given motherboard (see Figure 1-1). For a more detailed description of bus architectures and available types, please refer to Chapter 4.
Click Here To View Figure 1-1: A typical motherboard and its components
Power Supply
Because computers use electrical signals to communicate between the various system modules, a reliable source of power is required for a computer to function. Electrical power comes in two forms: alternating current (AC), which is the type that comes out of a wall outlet, and direct current (DC), which is the type that your computer uses. The power supply provides your computer with the electricity it needs by converting AC, or volts alternating current (Vac) into DC, also known as volts direct current (Vdc). This current is fed to your computer in one of several forms: ± 5 Vdc and ± 12 Vdc, with the "± " symbol denoting plus or minus.Earlier power supplies used a diode bridge to convert between current types. The power lost in the conversion of current is transformed into heat. The earlier power supplies were highly inefficient and tended to generate an excessive amount of heat. Newer power supplies, known as switching mode power supplies, use transistors in place of diodes to convert current and are much more efficient at converting power. However, they still generate quite a bit of heat. As a result, power supplies have a built-in fan that is used to prevent them from overheating. An overheated power supply will not only fail, but can damage other components inside the computer.
Exam Watch: Most people have a tendency to glance over these details. However, it is important that you know the voltages generated by the power supply as there will be a question or two on the exam.
Processor/CPU
With all of these electrical signals racing around the system board, a method of directing and controlling these signals becomes necessary. A device, known as the central processing unit (CPU), or merely the processor, fulfills this task. CPUs come in different shapes, pin structures, architectures, and speeds.Generally, the CPU is a square or rectangular chip that attaches to the motherboard through legs, called pins, located on the bottom of the chip. Rectangular chips are common in personal computers that predate the early 1980s, while newer chips are square. The chip itself contains millions of transistors that are arranged in an array. These transistors actually perform the work of directing electrical signals to their destinations and performing calculations.
The pins that attach the chip to the motherboard come in two forms: the Dual In-Line Package (DIP) and the Pin Grid Array (PGA). DIP pins are identified as two rows, located on opposing sides of the chip, of 20 pins. This form was used in chips manufactured prior to the very early 1980s. However, DIP chips are being replaced by the newer PGA chips as the standard. PGA chips are identified as four rows of pins that surround the bottom of the chip.
Memory
Just as you need a place at which to work, whether it is a desk in an office or on a countertop in a kitchen, your computer also needs a work area. This area, called memory, is used by the computer to store the instructions that comprise your applications and allow for the manipulation of data. Memory is comprised of integrated circuits (ICs) that reside on a chip. They work in a manner similar to a light switch in that each circuit can only have one of two states: on or off. Your computer recognizes an "off" switch as a numerical "0," while an "on" switch is translated as a numerical "1." This pattern of 0s and 1s, called binary, is how your computer stores, retrieves, and communicates data. Memory is actually broken up into several types: cache memory, random access memory (RAM), and read only memory (ROM).Cache memory stores information that is frequently accessed. By doing so, your computer cuts down on the possibility of data being moved out of physical memory and into logical memory (which is discussed in the following subsection), and makes your computer perform more efficiently. RAM works like cache memory in that it also stores data. However, data is written more frequently to this type of memory than any other type. ROM differs from the previous two memory types in that once you write to it, the data can’t be written over – hence the name "read only." ROM usually only stores the system Basic Input Output System (BIOS), which is the set of instructions that your computer uses to boot with.
Storage Devices
Information has become one of the most important commodities to individuals and businesses today. In the past, data was kept in the form of paper documents held in rows of file cabinets. Storing that information for any length of time became an almost impossible task due to space limitations. When personal computers began populating offices, their storage potential began to be explored. While the first computers used floppy disks and hard drives, today’s computers have a wider variety of storage media available, such as CD-ROMS, tape drives, optical drives, ZIP drives, and Jazz drives.Tape Drives
Shortly after the first computers were invented, it was discovered that magnetic tape could store information as a series of 1s and 0s. However, magnetic tape can only store data sequentially, and is most commonly used as a backup medium. As tape drives are not covered on the A+ Certification exam, but are frequently used in the real world, they only get a brief mention here.Floppy Drives
Floppy drives write data on disks that are inserted and removed from the drive. The actual disk is encased in an envelope, which has a small opening to allow a read/write head to access the disk. The read/write head passes over the disk, reading data from or writing data to the disk itself. Floppy drives, and the disks used by them, come in two sizes: 5.25" or 3.5".The 5.25" drives are the older of the two, and are seldom found in actual use today. The original single-sided drives only allowed for about 360 kilobytes (KB) to be stored on a disk. This was due to the fact that data could only be written to one side of the disk, hence "single-sided." Later drives were double-sided and were able to increase the storage capacity of the media ,bringing it’s capacity up to 1.2 Megabytes (MB).
As programs began to take up more space, the demand for higher capacity floppy disks increased. 3.5" drives emerged to fill this requirement, and added the extra bonus of using smaller disks encased in a more rigid medium. The first 3.5" disks only held 720 Kb, but capacity increased as technology progressed. While today’s floppy disks hold a range of 1.44 MB to 2.88 MB of data, the 1.44 MB drive is still the most common.
Hard Drives
Hard drives work in a manner similar to a floppy drive, but actually contain multiple disks stacked on top of each other inside of the drive itself. The disks reside on a rotating pole, called the spindle, and are in constant motion. Several read/write heads pass over the disk, allowing for a more rapid retrieval of data than the floppy drive. While the original hard drives only stored around 10 or 20 Mb, today’s personal computer drive capacities currently reach above 9 Gigabytes (Gb).CD-ROMs
Compact Disc Read Only Memory, or CD-ROM, drives have become increasingly popular, and are now a standard component of today’s computers. CD-ROMs are used more as a distribution medium than as a true storage medium, but this will change as CD-ROM writers become more affordable. The drive uses a laser instead of a read/write head to read data off of a compact disc, which is similar to the audio compact discs available at any music store.As applications increased in size, it became cost-ineffective for vendors to package software on floppy disk. CDs offer an average capacity of 650 Mb and allow software manufacturers to store their applications on a single CD as opposed to multiple disks. This saves the manufacturers quite a bit of money in postage and handling costs. In turn, it saves the customer time by not having to wait around the computer to swap disks. As a result, floppy disks have become the dinosaur of distribution medium.
Monitor
Monitors are an integral part of any computer system, and one with which you must become extremely familiar. However, monitors come in a wide variety of types, ranging from the original monochrome display adapter (MDA), which only permitted text-based characters, to today’s high resolution super video graphics adapter (SVGA).Depending on the type of monitor you are working with, the number of colors and screen resolution varies. However, all monitors function basically the same way. The back of the display screen, called a cathode ray tube (CRT), is coated with special chemicals, called phosphors, which glow when electrons strike them. An electron gun, controlled by a video adapter, resides inside the monitor and continuously shoots electrons at the CRT, panning across the monitor from left to right and top to bottom. This bombardment of electrons produces the text and graphics that you see. The adapter receives a character to be displayed from the computer and converts it into a series of instructions that the electron gun can understand, a process called rendering.
Different monitors have the ability to produce a different number of colors and resolution. The original monochrome monitor only supported one color and no graphics. The Hercules monitor was developed to include graphics, but it still only supported one color. Both of these monitors used digital adapters, which only allowed the output to be in a form of 0s and 1s.
Color Graphics Adapters (CGA) provided for four types of digital output. This output was defined with the red, green, and blue colors plus an intensity bit (RGBI). This meant that by combining all three colors, and changing the intensity of those colors, you could get a total of 16 different colors on the display (remember, digital output). However, the display could only show 640 pixels horizontally and 200 pixels vertically, referred to as 640 x 200, on the screen at any time.
The next improvement on the monitor was dubbed Enhanced Graphics Adapter (EGA) and added an intensity bit (RGBrgb) to each of the primary colors (RGB) to give a palette of 64 colors. However, while it could only display 16 colors at any given time, it improved resolution by enhancing the maximum pixel resolution to 720 x 350 for text mode and 640 x 350 in graphics mode, even though it still used the old digital output technology.
Monitors were ready for a revolution in technology, and the Virtual Graphics Array (VGA) gave it to us. It allowed for analog output, meaning that the adapter could control each RGB line independently. By doing so, the monitor is able to display up to 256 different colors at any given time from a virtually unlimited palette and resolution was improved to 720 x 400 in text mode and 640 x 480 in graphics mode.
Still, there was one more step in monitor technology to be explored, and it is probably the final step. Super Virtual Graphics Array (SVGAs) hit the market and brought us a color palette of over 16 million colors. The resolution jumped to 1280 x 1024, but it is more commonly used with 800 x 600 as the higher resolution requires special, and expensive, adapters. Monitor technology will probably improve upon the resolution, but will not add more colors to the palette as 16 million colors are more colors than the human eye can detect.
Monitors are used with adapters, or video card. As stated before, the adapter used must match the type of monitor that is connecting to it. This is because the adapter translates digital information from your computer into the appropriate signal type used by the monitor to generate the picture. If an incorrect adapter is used, the monitor will not work and will result in severe damage to the monitor and possibly even injury to you.
From the Field
Use That Screen Saver
There are many misperceptions and rumors regarding screen savers. In recent years, many people have come to the conclusion that they’re are just something fun to look at. They think that the monitors of today will not get any image burned into them. These people are wrong. In the field, I have seen monitors that have been turned on with the same desktop pattern for 24 hours and they have the image of the desktop burned into them rather deeply. These have been high-quality monitors, which were less than a year old.Choose your screen saver carefully. I’m sure you have seen the veritable plethora of available screen savers for your PC. Some are simple and some are quite complex. The complex ones usually have 3-D graphics and may contain animation or even have an interactive mode for the user to play a game or whatnot. Remember though that this comes at a price in terms of system resources. As you know, some system resources are very limited. If you are maxing out your system with a screen saver, you may be thrashing on the hard drive as your system is desperately swapping out memory to the disk just to keep this thing running. In the long run, this does run wear on the hard drive.
It has been rumored that the Windows OpenGL screen savers have one option that rarely, but every so often, renders a teapot instead of the tubes, which has been known to bring down systems. This can be tragic on a server. These OpenGL screen savers, and they are not alone, have been the culprit for many systems crashing. When troubleshooting a PC, especially in memory-related freezes and crashes after people come in after lunch, always look at the screen saver they are using as a possible cause. If you think it is their screen saver, change the saver back to the standard ones that don’t take up that much memory. It is truly amazing how many times this is overlooked.
— by Ted Hamilton, MCP, A+ Certified
Modem
Today’s society has come to rely heavily upon computer systems to facilitate the exchange of information. As a direct result, computers must also have the ability to communicate with other computers in order to send or receive information, regardless of the distance involved. Modems are not only one of the many devices that permit two separate computers to talk to each other, but they’re also one of the most common peripherals a technician will work with.Modems work by translating signals between a computer and a standard telephone line. A computer utilizes binary signals to read, process, store, and communicate data. However, the standard telephone line uses analog signals to carry sound waves, and therefore requires a much wider range of data than a computer. A modem takes data from the sending computer and translates it from digital signals into analog signals before transmitting it across a telephone line, a process called modulation. When a modem receives analog signals from a telephone line, it converts the data back into digital signals, a process called demodulation. As you’ve probably guessed, the word "modem" is merely an acronym for MOdulator/DEModulator.
Firmware
Firmware is one of those items that new technicians have a problem understanding. However, firmware is nothing more than special software and data files that resides in Read-Only Memory (ROM). An excellent example of firmware is the Basic Input-Output System (BIOS). The computer uses the settings stored in the BIOS to communicate with the operating system software. These settings are only changed if you enter the special SETUP program prior to booting the system.In some cases, you may need to upgrade the BIOS with a newer version. When you do this, you will need to use special software that is provided by the manufacturer to flash the BIOS. By flash, we actually mean that the special software will typically wipe the BIOS chip clean and then write the new BIOS onto the chip. Older BIOSs will not allow for this type of upgrade, which means that you will have to replace the chip if an upgrade becomes necessary. As the Year 2000 approaches, this may become necessary as some of the older 486 machines are not Year 2000-compliant.
Input Devices
Computers live for data, and to give them the data that they crave requires a means for them to accept input. Input devices take data from a user, such as the click of a mouse or the typing on a keyboard, and convert that data into electrical signals used by your computer. Several devices that provide input are: keyboards, mice, trackballs, pointer devices, digitized tablets, and touch screens.Output Devices
In order for your computer to be useful, it must provide data to you in some form, called output. Output devices take electronic signals from a computer and convert it into a format that the user can use. Examples of output devices include monitors, which were discussed in a previous section, and printers.Printers produce paper output, called hardcopy or printouts. Printouts can include text, graphical images, or both on the same page. Printers come in a variety of types, and many printers now include color. The most common printer types are: dot-matrix, ink jet, bubble jet, and laser printers. For a more detailed description of the various printers available, please refer to Chapter 5.
BIOS
As difficult as it is for you to keep up with all the peripheral devices available in the marketplace, not to mention the different models available from any given vendor, it is even more complex for your computer. And, as if things weren’t already rough enough, your computer needs to know how to communicate with every device attached to it, regardless of the operating system software used. The Basic Input/Output System, or BIOS, is the mechanism used by your computer to keep track of all this information and still remain independent of the operating system.The system BIOS is stored in read only memory, or ROM. When an application needs to perform an input-output (I/O) operation on a computer, the operating system makes the request to the system BIOS. The BIOS then translates the request into the appropriate instruction set used by the hardware device. This is similar to the function performed by device drivers, only at a lower level. This process also allows for different operating systems to smoothly communicate with devices located on the computer, as it provides a standard set of instructions that are recognized industry-wide.
CMOS
Different FRUs require different settings, such as interrupts, memory address ranges, and input-output ports. To inform the computer of all of the necessary operating parameters every time the computer boots up would, in effect, become tiresome. The CMOS, or Complementary Metal-Oxide Semiconductor, allows the computer to store this information even after the computer has been turned off.The CMOS is an integrated circuit composed of a metal oxide and is located directly on the system board. This material allows the circuit to operate at a very high speed, leading to a faster system boot. The CMOS is similar to RAM, in that data can be written to the chip. However, the only time that the CMOS should be modified is when a new component is installed, such as a hard disk drive or an internal peripheral card.
Adding and Removing Field Replaceable Modules
Because technology increases at an exponential rate, new forms of components come into being. These components have to be added to the computer or must replace, or upgrade, an existing one. In addition, some parts will fail as a result of being defective or worn out through use. Therefore, one of the most common tasks every technician has to perform is adding or replacing a system module.The first, and most important, step that you must take is to power off the computer and disconnect the power cord from the wall outlet. Powering off the computer helps to prevent you from being accidentally electrocuted by unintentionally coming into contact with circuits and/or components that may have live current flowing through them. By removing the power cord from the wall outlet, you are ensuring that if you mistakenly hit the power switch while working on the computer you will not have to worry about a trip to the hospital.
Before the cover can be removed from the computer, called the chassis, you must ground both the PC and yourself. This is due to the possibility of an ElectroStatic Discharge (ESD) that could damage you or the computer. ESD occurs when there is a difference in charge between one object and another, resulting in an exchange of electrons that equalize the potential between the two. In order to properly ground the computer, you must place the chassis on an ESD mat and connect one of the two wires to the computer. The second wire is connected to a ground pin that can be found on any electrical outlet. To ground yourself, you wear an ESD wrist strap and attach the wire from the strap to a ground. ESD and related procedures are more closely explained in Chapter 3.
After you have followed the ESD procedures, the cover can be safely removed. First, remove the screws that hold the cover in place. Some chassis also employ an operating latch to hold the cover in place. Ensure that you disengage any latches if in use. Then, slide or lift the cover from the chassis. Ensure that you place the cover in a location that is out of everyone’s way to avoid injury, including yourself.
At times, it will be necessary to remove expansion cards from the computer as they tend to get in your way. If needed, note their locations and any connectors that attach to them before removal to ensure that you will be able to put everything back into its appropriate spot. To remove cables and power connectors, simply grasp the connector and pull away from the component.
Adapter cards are held in place along the back plane of the computer by screws. Remove all screws holding the card in place and then get a firm grasp on both ends of the board. While using a gentle pulling motion, slightly rock the card from end to end. Some cards may need a bit more effort than others to get out of the expansion slot, but be careful not to exert too much force or you can damage the card and/or the system board. Repeat this procedure for all of the remaining cards that you need to remove.
The following subsections will assume that you have already completed the preceding procedures before continuing.
System Board
Prior to removing the system board, you need to remove all expansion cards, cables, and power connectors attached to the motherboard. Once this has been completed, you need to locate and remove any screws or plastic clips that attach the board to the computer. Once all fasteners have been removed, the system board can then be removed from the chassis.Once the system board is free of the case, take note of any jumper settings and/or DIP switch settings on the old system board and configure the new board in the same fashion. However, ensure that you have consulted the manufacturer’s instruction manual to ensure that none of the settings have changed. At this point, you can move the CPU and memory chips to the new board. Reverse the procedure used to install the replacement system board.
Power Supply
Power supplies are one of the easiest components to replace, as they do not require any jumper or DIP switch settings. The power supply is attached to the system board and the disk drives by power connectors. Follow the procedure in Exercise 1-1 to remove the power supply from your system.Exercise 1-1 Removing a Power Supply
- Mark the positions of the power connectors so that you can hook up the new power supply properly.
- Next, firmly grasp the connector and gently pull it from the socket. Never pull on the wires, as they are very easily damaged.
- Some power supplies have a cable that runs from the power supply to the power switch that must be disconnected as well.
- After all of the connectors have been detached, the final stage is to remove the mounting hardware used to hold the power supply in place. Depending on the power supply and mounting hardware, you may need to remove the four screws that hold it in place. With others, you can simply pull or slide the power supply out of the computer.
Click Here To View Figure 1-2: Installing a power supply
Processor/CPU
Some processors are attached to the motherboard by a Zero Insertion Force, or ZIF, socket. If your motherboard has one of these, you operate the lever to remove the chip. In other cases, you use a chip puller to gently grasp the sides of the processor. Use a gentle upward motion to remove the chip from its socket. Do not "rock" the chip as you remove it, because this can cause damage to the pins that attach the processor to the system board.If you are inserting a different speed or type of processor, you must reconfigure the system board. This is done through a series of jumpers or DIP switches that are located on the motherboard. As the board settings differ between the type of board and manufacturer’s specifications, refer to the manual provided with the board and configure it appropriately. If the documentation is unavailable, you may be able to consult the manufacturer’s Internet site for the correct settings.
Once the system board has been reconfigured, the manner in which you install the new processor differs depending on if you have a ZIF socket or not. If so, simply place the new processor over the socket and operate the lever, else position the processor over the socket and gently push down until the chip is seated. Reinstall any expansion cards or connectors that you removed previously and the installation is complete. A typical processor installation is outlined in Figure 1-3.
Click Here To View Figure 1-3: Installing a processor
Memory
To install memory, follow the procedure outlined in Exercise 1-2 and Figure 1-4.Click Here to View Figure 1-4: Installing memory
Exercise 1-2 Installing Memory
- Place the memory chip over the slot at a 45-degree angle.
- Gently push down on the chip and move it to an upright position until it clicks into place.
- Memory chips are keyed so that they can only fit into the slot one way. If the chip will not go into the socket, then the chip must be reversed.
- There are no CMOS settings to be concerned about, as memory is auto-sensed by the computer.
Storage Devices
There are several types of storage devices that are available for computers today, and that number is growing as technology improves. However, the most common peripherals that you will see are floppy drives, hard drives, tape drives, and CD-ROM drives. Hard drives are discussed in later sections under IDE/EIDE and SCSI.Floppy Drives
To remove a floppy drive, follow the procedure outlined in Exercise 1-3.Exercise 1-3 Removing a Floppy Drive
- Remove the faceplate from the front of the computer by gently pulling it away from the chassis.
- Remove the two restraining screws in the front of the chassis that hold the drive in place.
- Remove the power connector, located in the back of the drive, that runs from the power supply to the floppy drive. When you remove this connector, ensure that you grasp the connector and not the wires, as you could injure yourself by any static electricity that has built up or damage the power connector.
- Remove the floppy drive cable, which is a flat ribbon cable with a small twist in the wires located in the back of the drive that connects the drive to the floppy adapter.
- After all of the connectors are free, simply slide the drive out of the computer.
Click Here To View Figure 1-5: Installing a floppy drive
Tape Drives
Tape drives come in two forms, internal or external. With external tape drives, to add or remove them you merely plug or unplug the connector from the adapter located in the back of the computer. With internal drives, you need to remove the power connector and the tape drive cable. After the connectors have been removed, you simply slide the drive out of the computer. To install, you reverse this procedure and add one more step. Some tape drives require a device driver installation. This is accomplished through the operating system software. Consult with the manufacturer’s documentation for more specific details.CD-ROM Drives
CD-ROM drive removal and installation is similar to a tape drive with two exceptions. The first is an extra cable that connects the CD-ROM drive to either the controller or the sound board. This cable is used to transmit audio signals from the CD-ROM drive to the controller/sound board. The second difference is that a CD-ROM drive always requires a device driver installation through the system software. Again, consult with the product documentation to obtain more details on the particular model you are installing. A typical installation is outlined in Figure 1-6.Click Here To View Figure 1-6: Installing a CD-ROM drive
Monitor
Although most of the equipment you will deal with isn’t too badly out of date, monitors of all types are still in use today, including the old monochrome monitor. When you remove a monitor, you simply unplug it from the back of the computer. If it is a monochrome, Hercules, CGA, or EGA monitor, it is a digital monitor and will have a female D-9 connector that plugs into a digital adapter. If it is a VGA or SVGA monitor, it will have a female D-15 connector that plugs into an analog adapter also located in the back of the computer. Never plug a digital monitor into an analog adapter, or vice versa, as severe damage will result.If you need to remove the graphics adapter card, make sure that you note any cable connections to the adapter before removing them. The adapter card itself is held to the chassis by a single screw that must also be removed. Then, gently pull the card out of its socket. To install, simply reverse the procedures. However, if you are installing a different type of monitor, ensure that you install the video’s device drivers into the operating system. Without changing device drivers, the monitor will not work correctly, if at all.
Modem
If you are removing an internal modem, you must ensure to detach the phone cord from the back of the computer before removing the modem card. At that point, you can remove the single screw that holds the modem in place and gently pull upward on the card until it is free from its socket. If it is an external modem, you simply unplug the device from the back of the computer.To install a modem, you merely reverse the procedures for removing it.
Input Devices
Several forms of input devices are available, such as keyboards and mice. Keyboards are the easiest component to install, as you simply plug them into an available port in the back of the computer. There are two types of keyboard connectors in use, the DIN-5 connector and the Mini DIN-6 connector. DIN-5s are generally found on AT style keyboards and have a round port with 5 pins. The Mini DIN-6 came out with the release of IBM’s PS/2 machine, and also has a round port but differs in that it has 6 pins with one square pin.There are several kinds of mice available, and thus several connectors in use. If you have a serial mouse, it uses a serial DB-9 connector and requires a free COM port. A bus mouse will use a DIN-6 connector and require a free IRQ. The last type of mouse is the PS/2 mouse, which is similar to the bus type except that it has to have an expansion card installed to use it. Once you have connected the mouse, you have to install the device driver in the operating system software.
While there are a variety of other input devices available, you will not need to know about them for the A+ Certification exam, and thus they are not explained here.
Output Devices
Output devices come in various forms, but the standard devices tested on the A+ exam are monitors and printers. As we have already discussed monitor installation in an earlier section, we will discuss printers in this section.Printer installation usually requires a cable, a power outlet, and device drivers. The printer cable, which is a flat ribbon type or a round shielded cable, attaches to a parallel port in the back of the computer. Printers have their own power supply inside the unit and must be connected to a power outlet. Once this has been completed, the device driver that shipped with the printer must be installed in the operating system software. To remove a printer, simply reverse the procedures.
IRQs, DMAs, and I/O Addresses
In order to ensure that information is passed between the system modules and the CPU in a timely fashion, devices must be able to directly communicate with the CPU. Because the processor is a busy device, system components must first get the CPU’s attention. This is accomplished through a special set of lines, called interrupt request lines (IRQs), in the bus. IRQs are given a number, ranging from 0 through 15, to identify them. In turn, devices are given an IRQ to use. However, with most BIOSs, no two devices in the computer can use the same IRQ or else the processor won’t know who is calling it. Some of the newer BIOSs support IRQ sharing, but you need to consult with the vendor’s documentation to see if this feature is supported.Once the CPU receives an IRQ from a device, it can directly communicate with that device through I/O addresses or I/O ports. I/O ports are assigned a range of numbers, which are in turn assigned to specific devices. As with IRQs, no two devices can use the same I/O address.
There are times when a component needs to write information directly into main memory. When a device has to do this, it uses a channel, called a Dynamic Memory Access (DMA) Channel, to do so. This method improves the module’s performance as you are basically removing the overhead of having the processor move the information from the device to main memory.
Standard IRQ Settings
The computer industry has come up with a set of standard IRQ settings. These settings should be used whenever you are installing a device. Table 1-1 lists the standard IRQ settings.| IRQ Number | Standard Device Assignment |
| NMI (nonmaskable interrupt) | Memory parity error |
| 0 | System timer |
| 1 | Keyboard |
| 2 | Cascaded to IRQ 9 |
| 3 | Serial port (COM2) |
| 4 | Serial port (COM1) |
| 5 | Parallel port (LPT2) |
| 6 | Floppy controller |
| 7 | Parallel port (LPT1) |
| 8 | Real-time clock |
| 9 | Redirected as IRQ2 |
| 10 | Available |
| 11 | Available |
| 12 | Mouse |
| 13 | Math co-processor |
| 14 | Hard disk controller |
| 15 | Available |
Standard I/O Address Settings
In addition to standard IRQ settings, you need to know the standard I/O address settings. Table 1-2 lists the more frequently used port addresses.| Port Address (hex range) | Device |
| 1F0-1F8 | Hard drive controller, 16-bit ISA |
| 200-20F | Game control |
| 201 | Game I/O |
| 278-27F | Parallel port (LPT2) |
| 2F8-2FF | Serial port (COM2) |
| 320-32F | Hard drive controller, 8-bit ISA |
| 378-37F | Parallel port (LPT1) |
| 3B0-3BF | Monochrome graphics adapter |
| 3D0-3DF | Color graphics adapter |
| 3F0-3F7 | Floppy controller |
| 3F8-3FF | Serial port (COM1) |
Exam Watch: Know your I/O addresses like the back of your hand. You will encounter several questions on the exam pertaining to I/O addresses.
Differences Between Jumpers and Switches
Interrupts, I/O addresses, DMA channels, and some additional features have to be configured in the hardware. Jumpers and Dual In-Line Package (DIP) switches are used to accomplish configuration.Jumpers are actually made of two separate components. The first component is a row of metal pins on the hardware itself. The second component is a small plastic cap that has a metal insert inside of it. The two parts together form a circuit that sets the configuration. This form of configuration device is only used to set one value for a feature at a time.
DIP switches have an advantage over jumpers in that they can be used to configure multiple settings. DIP switches are very tiny boxes with switches embedded in them. Each switch sets a value of 0 or 1, depending on how they are set. You will see two forms of DIP switches in use, but the only difference between the two is the method by which you set the switch. One type of switch is a miniature flip-toggle type switch, and the second type is a slide type switch.
Locating and Setting Switches/Jumpers
Regardless of the type of configuration device used, you must locate and set them according to the directions found in the component’s documentation. On hard drives, these switches are generally found near the connectors. However, on system boards or expansion cards, you must look around the card. There is no true hard and fast rule used to locate them, but setting these devices can be a bit difficult. To make things a bit easier on yourself, use a pair of tweezers to install a jumper and use a pen or pencil point to set DIP switches, and follow the manufacturers guidelines for installing. Figure 1-7 shows a typical jumper installation.Click Here To View Figure 1-7: Jumpers
Modems
Modems may or may not need to be configured with an IRQ and I/O address depending on what type they are. If they are external devices, they will use an existing serial port on your computer and therefore do not need the IRQ or I/O address. However, if they are internal devices, you will definitely have to configure these values. Computers today now have four COM ports, labeled COM1 through COM4. You must choose an unused COM port and I/O address in order to get the modem to function correctly, but most modems are now configured to use either COM3 with an I/O setting of 3E8-3EF or COM4 with an I/O setting of 2E8-2EF. In addition, you need to select a free IRQ. To be sure that these settings will work with your modem, consult the manufacturer’s documentation.Sound Cards
Sound cards have become popular thanks to the gaming industry. Imagine trying to shoot the bad guys with your space ship without having sound to hear those marvelous explosions. Creative Labs has been the industry leader in the sound card business, and as such has set the standard. Typically, sound cards have the following configuration: IRQ 5, DMA 1, and I/O Address 220. These are standard numbers used with SoundBlasters, but as always consult the manufacturer’s documentation in case you have one of the esoteric kinds.Network Cards
Network cards are becoming more common as networks have proven to be a cost-effective method of sharing information. Network cards need to have an IRQ, I/O address, and a memory address configured both on the card and in the device driver. Different forms of network cards, such as Ethernet or Token Ring, have different standards as to their configuration. Figure 1-8 shows the correct procedure for seating an adapter card, but consult with the manufacturer’s documentation for the appropriate settings.Click Here To View Figure 1-8: Seating an adapter card
Peripheral Ports, Cabling, and Connectors
As a computer technician, your clients expect you to be extremely knowledgeable about every facet of a computer’s operation. Unless you are one of those lucky few individuals who have been blessed with a photographic memory, this is an almost impossible task. However, you can use a combination of documentation, knowledge, observation, and deductive reasoning to figure out an unfamiliar component’s operation, installation, and configuration. In this respect, you become a sort of computer detective, and like any good investigator, you must at least learn the basics of your trade. As you will be working with many different types of FRMs, you need to have a good working knowledge of the various kinds of cables, peripheral ports, and connectors associated with them.Cable Types
The function of a cable is to transmit electronic signals from one device to another. It does this by sending the signal over some form of medium, such as copper wire or fiber-optics. The medium is enclosed in a tube or a ribbon sheathing in order to protect it from damage. Cables come in two different forms, shielded cables and unshielded cables, as shown in Figure 1-9. Shielded cables have a wire mesh or Mylar layer added in between the medium and the sheathing that protects the cables from interference. Signals normally follow the medium across the line, but sometimes a signal or stray electrons will stray into the atmosphere producing noise, which is known as crosstalk. The extra layer also adds strength to the cable itself. Unshielded cables do not have this extra layer.
Figure 1-9: Common cable types
Cable and Connector Location – Internal/External
Cables are used to connect peripherals to adapters. Peripherals generally have the connector located in the back of the device while adapters typically have the connector located on the side of the card. Some adapter cards have the connector extending out of the computer in order to enable connection with external devices, while others have it on the side of the card for internal devices.Serial Versus Parallel
Serial and parallel communications are defined by their transmission characteristics and primary control signals. We explore these forms of communication in the following subsections.Serial Communication
Serial ports are used for serial communications. Serial communications follow an RS-232C standard. When a device transmits data serially, it is actually transmitting the bits of information sequentially over a single conductor. However, there are two methods used to transmit the data, synchronous and asynchronous.Synchronous communication uses a single clock circuit in the transmitting device to synchronize the data transfer and set the rate of transmission. This synchronization defines the start and end of the data. With asynchronous communications, both the sending and receiving devices have their own clock circuits. Synchronization is established by inserting a start bit in front of the data to be transmitted, and placing one or two stop bits after. With the overhead required by asynchronous communication, synchronous communication is much faster.
The primary control signals are summarized in Table 1-3.
| Control Signal | Description |
| Serial Data Out (TxD) | Used to transmit data. Output from the computer to the device. |
| Serial Data Receive (RxD) | Used to transmit data. Input to the computer from the device. |
| Data Terminal Ready (DTR) | Used to tell the receiver that data is ready to be sent. Usually connected to the DSR on the receiving hardware. Output from the transmitting hardware’s side. |
| Data Set Ready (DSR) | Used to tell the receiver that data is ready to be sent. Input on the receiving hardware’s side. |
| System Ground | Ground reference voltage between the two devices. |
Parallel Communication
Parallel communications transmit data over eight parallel conductors. The signals are broken down into two types, data signals and control signals. Control signals are used to control functions or synchronize the devices, called handshaking, while data signals contain the actual information. When data is sent out using parallel communications, it transmits one byte at a time versus the one bit transmitted by using serial communication.The primary control signals used in parallel communications are summarized in Table 1-4.
| Control Signal | Description |
| Acknowledgement | Used to inform the transmitting device that data was received and the receiver is ready for more. |
| AutoFeed | Used by the processor to inform a printer to generate an automatic line feed. |
| Busy | Used to inform the processor that the receiving device cannot receive data. |
| Error | Used by the receiving device to indicate an error condition. |
| Init | Used by the processor device to initialize the receiving device. |
| Slct | Used by the receiving device to acknowledge a Slctin. |
| SlctIn | Used by the processor to select the device. |
| Strobe-Asserted | Used by the receiving device to inform it that valid data is present on the data lines. |
Exam Watch: Memorize the primary control signals for the exam. There are several questions that refer to both parallel and serial communications.
Pin Connections
Each pin on a connector is used to carry control signals back and forth from the device. For a listing of the control signals used in serial and parallel communications, please refer back to Table 1-3 and Table 1-4, respectively.Cable Handling/Routing
When you handle cables, you must be careful with them as they are more easily damaged than you may think. Never place cables near the power supply or other high-voltage equipment, as the heat generated could cause damage to the cable. Also, interference with the signals that travel along the cable from high-voltage equipment could cause problems with the proper function of devices that will still try to interpret corrupted signals.Types of Connectors
Connectors come in two standard flavors, male (pins) or female (sockets). The names in parentheses are due to a new wave of political correctness sweeping through the computer industry that has decided to rename the connectors to something more "acceptable" to society. Male connectors are distinguished by possessing rows of pins, while female connectors are characterized by having sockets. When you attach a connector to a device, you are actually attaching it to another connector. For example, if you are connecting a keyboard to a computer, you are using a male connector to link up with a female connector on your I/O adapter.In addition, there are several categories of connectors in use. While there are too many to define, we discuss the connectors most commonly found on the exam.
DB9
DB9 connectors are distinguished by their trapezoid appearance. There are 9 pins in the connector, 5 pins in the bottom row and 4 pins in the top row. This type of connector is most commonly used for video display devices and serial ports.DB25
DB25 connectors are similar to DB9s in that they are trapezoidal in shape. There are 25 pins set into two rows on the connector. This type of connector is used for parallel and serial ports.RJ11
RJ11 connectors are the same connector that is used to attach a phone line to a phone. It is also used to link a modem to a phone line. These connectors only have 4 pins, and clip into the modem.RJ14
RJ14 connectors are dual-line phone jacks that can handle up to two phone lines. These types of connectors are not very common in the industry.RJ45
RJ45 connectors are most commonly used to attach an unshielded twisted pair (UTP) cable with a network card. These connectors have 8 pins, and are similar to the RJ11 connector. This is the most common connector used on an Ethernet network.PS2/MINI-DIN
PS2/Mini-Din connectors are most commonly used for mice and keyboards. These connectors have 6 pins, composed of 5 round pins plus one square pin.Installing and Configuring IDE/EIDE Devices
The earliest hard drives, the ST-506 and the Enhanced Small Device Interface (ESDI), had to utilize a device known as a controller in order for the drive to function. The controller’s job was to interpret commands from the CPU into the instructions needed by the hard drive. For example, if the CPU was told to write data to the hard disk, it would pass the request to the controller. The controller would create a set of instructions that would tell the hard drive how to position the read/write heads over the disk, and then actually read the data. Once the drive got to the data, it would send it back to the controller, which would then pass it back to the CPU.Controllers complicated the installation of hard drives because they were an additional circuit board that had to be configured and installed in the computer. Integrated Drive Electronics (IDE) drives simplify hard drive installation by integrating the controller into the drive itself, and it is because of this that IDE drives gained popularity in the computer industry. However, IDE drives are limited by the fact that they are restricted to about 528 MB. The Enhanced IDE (EIDE) drives were created to overcome this limitation, and can be found in a variety of sizes in the gigabyte range.
However, before installing an IDE or EIDE drive, you must have a hard drive adapter connected to the motherboard. Some of the more recent system boards already have an IDE/EIDE adapter built-in, which saves you some work, but if it is an older board you merely plug the adapter into the system board. Once the adapter is in place, you can install the drive into the computer, as outlined in Figure 1-10. The drive is attached to the adapter using a 40-pin cable, which is similar to the floppy drive cable we discussed earlier except that it doesn’t have a twist.
Click Here To View Figure 1-10: Installing a hard drive
The last phase of your installation is to configure the computer’s CMOS. Without completing this step, the computer won’t even know that the hard drive is there. When you turn on the computer, you should see a message on the screen that states to press a key, or keys, for SETUP. On some of the newer computers, you have to pay strict attention to the monitor or you may miss this message. When you press the key combination that brings up the Setup program, enter into the Fixed Disk section and enter in the appropriate information needed by the computer’s CMOS. This information generally includes items such as the number of sectors, cylinders, and heads that the hard drive has. You can usually find all of the correct configuration information imprinted on the drive itself or in the accompanying manufacturer’s documentation.
Master/Slave
The preceding installation information works if you have only one drive to install, but what if there is an existing drive in the computer or you have to install multiple drives at once? The installation is performed the same way as previously discussed up to the point where you actually install the drive itself. At this point, installation becomes slightly more complex due to the fact that each drive has a controller built into the device itself. The adapter that is attached to the hard drive cable would get confused as to which controller was "in charge." This problem is resolved through the master/slave relationship.Basically, one drive becomes the master drive. All commands that direct any hard drive’s operations are passed through the master’s controller. The rest of the drives are then said to beslaves to the master, as their controllers have no say in the drive’s operations. Configuring the master/slave drives is accomplished by setting the appropriate jumpers on the individual drives before you install them. First, consult the manufacturer’s documentation for the correct jumper setting, set the jumpers accordingly, and install the drives. The rest of the installation is completed as before.
Devices per Channel
There is one last feature of IDE/EIDE hard drives that you must be aware of. If you are using IDE drives, you can only have up to two drives installed. This is a limitation of the technology. However, with EIDE drives, you can have up to four drives installed but you will only be able to put two drives on a single cable. In order to have three or four drives, you need a separate cable that is connected to the second connector on the EIDE controller. Each connector on the EIDE controller is given a channel number. The first channel is Channel 0 (primary) and the second is Channel 1 (secondary).Installing and Configuring SCSI Devices
Small Computer Systems Interface (SCSI), pronounced "scuzzy" in the computer industry, has become more popular in the PC field recently. These devices permit you to connect multiple devices to one cable, or "chain" them, in configurations of up to 7 to 15 devices on a single cable depending on the SCSI implementation that you are using. In order to properly install or upgrade SCSI devices, there are several things that must be taken into consideration and are discussed in the following sections. We will first discuss the types of SCSI devices that are available.Types of SCSI Devices
As technology improves, new forms of devices and standards become available. The organization that defines the SCSI standard is the American National Standards Institute (ANSI), and was responsible for releasing the first SCSI standard in 1986. Since then, SCSI has gone through several evolutions. The types of SCSI devices that you may encounter are the topic of the following subsections.SCSI-1
The original SCSI device had an 8-bit bus that was attached to the devices using either female DB-25 or Centronics-50 connectors. It’s data transfer rate was a maximum of 5 megabytes-per-second (MBps), and was the fastest drive on the market. However, vendors did not adhere to the standard and made a few small changes in their implementation. As a result, some SCSI devices would interfere with the correct operation of other SCSI devices. This made them a major headache to install and configure when those differences made themselves known.SCSI-2
In 1994, ANSI released a new standard that was aptly named SCSI-2. This standard allowed for backward-compatibility with the original SCSI-1 devices. However, three different variants of the device have been released because of the different options that the standard permitted. One of the variants, named Wide SCSI-2, included a 16-bit bus that enabled large data transfers to be more efficient. Fast SCSI-2 was another option that increased the data transfer rate to 10 MBps. However, the final variant combined the features of both options to create Fast-Wide SCSI-2. This combination yielded a 16-bit bus with a total transfer rate of 20 MBps.SCSI-3
Because the SCSI-3 standard is so new, relative to the A+ Certification exam, there really isn’t anything about them that you need to study for the exam. However, the information is included here to as a reference point for real-world situations.SCSI-3 is the latest SCSI standard issued by ANSI. Like SCSI-2, SCSI-3 also provides for extra options, and at the time of this writing there are only two variants on the market. The first one goes by the names: Double Speed SCSI, Fast-20 SCSI, and Ultra SCSI. It was developed for high-performance SCSI devices and comes on an 8-bit bus with a 20 MBps transfer rate. The second variation goes by the labels Wide Fast-20 SCSI, Wide Double Speed SCSI, and more currently Wide Ultra SCSI. It’s characteristics are a 16-bit bus with transfer speeds at a maximum of 40 MBps.
Address Conflicts
When you want to send a letter somewhere, you typically address it with a house number, a street name, and so forth. This information enables the post office to deliver it to the correct location. Computers also have an addressing scheme that enables them to send and receive messages amongst the various devices attached to it. Each address must be unique, just as the post office requires a unique address for every house, apartment, and condominium. If the address isn’t unique, messages can be misdirected to the wrong device, leading to an unpredictable variety of problems or even a non-functioning computer. Legal addresses depend on the type of bus you are using, but the values are as follows: | 8-bit bus: starting address = 0 ending address = 7 |
| 16-bit bus: starting address = 0 ending address = 15 |
| 32-bit bus: starting address = 0 ending address = 31 |
One last thing to take into consideration when addressing devices is to follow standard industry practices. While not necessary for the exam, it helps to conform to the procedures that the industry has agreed upon. The following list gives the commonly accepted addressing schemes.
| The adapter is given the highest priority, ID 0 for PS/2 machines or ID 7 for most others |
| The first hard disk, or bootable disk, is given the next available ID number, ID1 for PS/2 machines and ID 0 for most others |
| CD-ROM devices are given ID 3 |
| Slower devices are generally given a higher priority because they take up most of their time processing requests rather than sending them |
Switch and Jumper Settings
SCSI devices must be manually set to an address prior to their installation. This is accomplished through a series of jumpers or DIP switches located on the back of the device. In order to correctly configure the address, consult the manufacturer’s documentation for the appropriate settings. If the documentation is unavailable, configuration information may be found at the manufacturer’s Internet site.Cabling
The kind of cable used to connect SCSI devices is dependent upon whether or not it is an internal or external device. Internal devices use a single, unshielded 50-pin cable that is similar to the 40-pin IDE hard drive cable. The connectors used in this case are keyed Centronics-50 connectors. External devices, on the other hand, use short, thick, shielded cables that can have either a female DB-25, Centronics-50, Mini 50, or Mini 68 connector attached on it. This type of cable, called a stub cable for its length, is used to daisy chain the SCSI devices together in the following manner: | The first cable attaches the adapter to the first device, or device number 0 |
| The second cable attaches device number 0 to the second device, or device number 1 |
| The third cable, if any, attaches device number 1 to the third drive, and so on |
Termination Conflicts
Armed with a unique address and attached to the bus, the circuitry on the SCSI device takes over. When a signal is sent out on the bus, only the device that corresponds to the correct address responds to the adapter. However, that signal doesn’t stop at the device but instead continues traveling along the bus. To prevent these signals from escaping the bus and possibly causing interference, also known as crosstalk, to other devices, a terminator must be attached on both ends of the bus. Some devices and adapters have the terminator incorporated into the device, in which case you can enable or disable the terminator using a jumper or a DIP switch. In other cases, an external resistor is used to terminate the bus at the adapter and cable end.Power Supply
Without power, no computer component in existence can function. SCSI devices obtain their power depending on the type of device it is. Internal components draw their power from the regular power supply found inside the computer. On the other hand, external components come with their own power supplies. This can be a disadvantage if your power strip is already overburdened or out of connectors.Internal Versus External
As you have seen in the previous discussions, there are some differences between internal and external SCSI components. These differences also complicate the installation process, thereby making the method dependent on the type of devices you will be installing. The preparation done prior to the cabling of the devices is the same and is discussed first.The first step in almost every installation is to follow your ESD procedures prior to removing the computer case. Once you have completed these procedures, remove the case and any other devices and/or cables that may be in your way. Then, configure the addresses of each SCSI device that will be installed by consulting the documentation for the correct jumper or DIP switch settings. As you configure the addresses, lay them out on your electrostatic mat in sequential order by the address number, starting with zero. By doing this as opposed to waiting until the cable is attached, you will save yourself some grief. At this point, the rest of the installation process will be determined upon the types of devices to be installed: internal only, external only, or a mix of the two.
Internal SCSI Devices Only
When all of the devices are internal, the installation goes very smoothly. Because you have already laid out your components, you know which device is at the end of the chain. On this device, install the terminator. If the device has a terminator built-in, consult the documentation for the appropriate jumper or DIP switch setting needed to enable the terminator. On the rest of the components, ensure that any terminators are removed if they have them present, or that any built-in terminators are disabled. Next, you must install, or enable, the adapter’s terminator. Once you have completed setting up your terminations, you can begin mounting the devices into the computer.Some chassis allow you to slide the devices into the case and then just attach two screws in the front to hold it in place. With others, you must attach the device to mounting hardware using four screws before installing it. Regardless of which method you must use, when you have completed the physical install it is time to attach the cable to your devices. Start with the adapter, and just plug the cable in. The cable should be attached to each component that you have installed. With internal devices, the order in which devices are attached does not matter, but based on practical experience, always cable SCSI devices sequentially. This not only ensures that you do not forget to do so with external devices, as you see in the next subsection, it also guarantees that there is no confusion later on as to the device’s address number. If you ever have to go back and remove a defective or failed component, you know exactly which device it is without pulling out the rest of the devices.
At this stage, you can proceed to replacing any expansion cards or cables that were previously removed and boot the computer to configure the new drives.
External SCSI Devices Only
When all of the devices are external, the installation is only slightly different than the procedures used to configure internal components. Because you have already laid out your components, you know which device is at the end of the chain. On this device, install the terminator. If the device has a terminator built-in, consult the documentation for the appropriate jumper or DIP switch setting needed to enable the terminator. On the rest of the components, ensure that any terminators are removed if they have them present, or that any built-in terminators are disabled. Next, you must install, or enable, the adapter’s terminator. Even though external devices are easier to get to, it is still a good idea to complete the termination phase first to keep your procedures as uniform as possible. Once you have completed setting up your terminations, you can begin mounting the devices into the computer.Some chassis allow you to slide the devices into the case and then just attach two screws in the front to hold it in place. With others, you must attach the device to mounting hardware using four screws before installing it. Regardless of which method you must use, when you have completed the physical install it is time to attach the cable to your devices. Because you will be using stub cables to connect your components, start by attaching the adapter to device 0. Next, use a second stub cable and connect device 0 with device 1. Repeat this procedure until you have reached the end of the chain. Remember when you laid out the devices sequentially? The reason for doing so is that external devices require that you cable them in order by their device number. If you get the components out of order, you will get unpredictable results including the possibility that the computer will not boot.
At this point, replace any cables or expansion cards that were previously removed and boot the computer for configuration.
Internal and External SCSI Devices
When you have to install a combination of internal and external devices, it is known as a hybrid environment. Hopefully, when you laid out the components during the addressing phase, you also separated the internals from the externals. When you terminate the chain in a hybrid environment, you do not terminate the adapter. Instead, you terminate the device on the end of the internal chain and the device on the end of the external chain. As with the previous two installation methods, install or enable the terminators on the last device on each chain, then remove or disable the terminators on all other components (including the adapter).Exam Watch: Some vendors have adapters that require you to install or enable the terminator on the adapter as well. If your SCSI components are not being recognized by the computer, try installing or enabling the terminator. However, when you take the exam, assume that these kinds of adapters do not exist.
Configuration
With all of your SCSI devices addressed, installed, terminated, and cabled together, it is time to tell the computer about them. However, the procedure used depends on whether or not you have a bootable SCSI device installed. If there is a bootable device, you must enable the BIOS on the adapter card. This is performed through a jumper or DIP switch setting that should be listed in the adapter’s documentation. Once the BIOS is enabled, you configure the adapter to use a memory area located in reserved memory. Again, you must consult the documentation for the appropriate address and setting information.If your device is not bootable, such as a SCSI printer or CD-ROM drive, you must load a device driver in the operating system software. The driver itself should have come on a floppy disk with the SCSI adapter card, but in some cases you may need to visit the manufacturer’s Internet site to get it. Be aware that sometimes there might be problems with the drivers themselves, as problems have a tendency to show up after the adapters have hit the market. If you encounter problems, try visiting the manufacturer’s Internet site for an updated driver or a small piece of software, called a patch, that will resolve the difficulty.
Installing and Configuring Peripheral Devices
As peripheral devices are the most frequent modules that need to be installed or replaced, it is critical that you understand how to install the many common components available. The following subsections will describe how to install and configure common devices that you should be familiar with.Remember that when you work with any computer, you must follow ESD procedures. This requires you to ensure that the computer itself is on an electrostatic mat and attached properly, as well as guaranteeing that your electrostatic wrist band is properly secured on your person. The only time that you would not wear the wrist strap is when you are working with monitors. Never wear a wrist strap when working on monitors as the static electricity that has built up can kill you.
Once you have your ESD procedures completed, you need to remove the screws in the back of the computer to remove the case. These screws are located around the edges of the computer. Some cases must be unlatched before you slide them out, but usually you just have to slide the cover up and away from the computer. Make sure that you place the cover out of everyone’s way, including yourself, to avoid unnecessary injury.
With some components, you may be required to remove various expansion cards or connectors that may be in your way. If there are any such cards or connectors, remove them only after marking their placement and connections. This will save you some grief during the installation process.
Monitor/Video Card
Before installing a new monitor, you must take note of whether this is a different type of monitor than was previously installed, for example upgrading from an EGA to a SVGA. If so, you will require a new video adapter as well. If you are only replacing a monitor of the same type, take note of the models, as different model monitors require different software drivers.Either way, follow the procedures in Exercise 1-4 when installing the card.
Exercise 1-4 Installing a Monitor/Video Card
- Power off the monitor and unplug it from the back of the computer.
- If you are replacing the adapter card, make sure that you note the connectors that attach to the card as the new card will probably have the same connector setup, then remove the connectors.
- Remove the single screw that holds the card to the chassis, then gently pull upwards and away from the computer. If you apply too much force, you may damage the card.
- Once it is free, replace the card with a new one by reversing the procedures. If the new card doesn’t go into the slot easily, you may have the card reversed. Most adapter cards are keyed to ensure that they only fit into the socket in the correct manner.
- After replacing any adapter cards, you can now plug the new monitor into the computer.
- When you boot the computer, you must install the appropriate device drivers if it is a new type of monitor or a different brand. Make sure that you follow the manufacturer’s documentation when installing new monitors. If you are working with a Windows 95 machine, it will probably detect the new component and step you through the installation.
Modem
Most of today’s modems use either COM3 or COM4 for the port. When you install a modem, check the back of the computer for any other connections going in. Sometimes, to position a modem so it’s easy to get at later for troubleshooting purposes, or to change phone lines going into the computer, you may need to move an expansion card to another slot.Modems come in two forms, internal or external. External modems only need a free COM port, and can plug into an existing serial port in the back of the computer with an RS232-compliant cable. However, with an internal modem, you must make sure that you already have a free IRQ, I/O address, and COM port prior to installation. To install an internal modem, you must attach it to one of the expansion ports inside the computer and install the screw that holds it in place. The IRQ, I/O address, and COM port information is configured in the operating system software.
Storage devices
Installation and configuration of the various storage devices have already been discussed in previous sections. For floppy drives, tape drives, and CD-ROM drives, please refer back to the section on Adding and Removing Peripheral Devices. If you need to reference information on hard drives, please refer to either the Installing and Configuring IDE/EIDE or Installing and Configuring SCSI Devices sections for the appropriate type of drive.Associated drivers
Various peripherals require that a device driver is installed into the operating system. With MS-DOS systems, the information is placed in the AUTOEXEC.BAT or CONFIG.SYS files. With the more popular Microsoft Windows 95, the operating system will detect the new component upon boot and step you through the process of installing the driver if there isn’t already one available to the system. Depending on the operating system with which you are working, consult with the documentation provided by the manufacturer to ensure that you install the driver correctly.Functions and Use of Common Hand Tools
In order to install or upgrade computer hardware, you must have a good set of tools. Nothing is more frustrating than going to a customer site and not having the proper equipment with you, and worse yet, the customer will get the impression that you may not know what you’re doing. There are several items that should be included in any toolkit, and they are discussed in the following sections.Screwdrivers
The most common tool found in every technician’s toolkit is the screwdriver. Screwdrivers come in various sizes and types. The usual assortment of screwdrivers include: flat-blade, Phillips, and Torx, all discussed in the following subsections.Flat Blade
Flat blade screwdrivers are common and easily recognizable by their flat blade or "flat head." The screws have a single slot that runs dead center across its head. While older computers may still use these types of screws, more modern ones seldom do. The reason is that the metal around the slot has a tendency to be easily damaged by the force used to turn the screw, causing the need to replace the screws more often. If you’ve ever had to remove a case from a computer, you’ll know how stubborn some screws are to remove, especially if it hasn’t been used in awhile. Phillips, and more recently Torx, screws are more commonly used.Phillips
The Phillips screwdriver provides more protection against damaging the head of the screw, and is used more frequently in the computer industry. The blade of the screwdriver is in a cross-shape, tapering down to a point. The screw itself has two slots that form an "X" or a cross, depending on how you view it. The extra slot allows for the screwdriver to more evenly distribute the force exerted on the screw itself, reducing the potential for damage to the screw. When buying bits or screwdrivers, note that Phillips uses a number system, such as #2, to denote the size of the blade. Ensure to get several different sizes into your toolkit.Torx
The Torx screwdriver looks very similar to the Phillips screwdriver with it’s cross shape, except that it has an extra blade that runs through the center of the cross, giving it the appearance of a "star." This gives even more protection from damage to the screw itself. Currently, you will usually only need this type of screwdriver to work on MacIntosh or Compaq system, but the popularity of this type is increasing. Torx screwdrivers also use a numbering system to denote the size of the blade, but are given a "T-" instead of the pound (#) sign.Chip-puller
In order to remove integrated circuits, a special type of tool, called the chip puller or integrated circuit (IC) puller, is used. The standard IC puller is U-shaped, and has small fingers on the ends that slip between the socket and the chip itself. These fingers ensure that the force used to pull the chip from the socket is spread equally between the two sides to reduce the possibility of damage to the chip. Once you have the puller on the chip, gently pull until the chip comes out of the socket.Never try to remove an integrated circuit with your fingers. For one thing, you could damage the pins that attach the chip to the board. Another reason is that static electricity has a tendency to build up inside the computer. If a static discharge should occur due to the potential difference between yourself and the chip, damage could occur. Another "no no is to attempt to use a pair of pliers or tweezers on chips. These tools magnify the force that you apply to them, risking an overexertion of force and hence damage to the chip.
Multimeter
Computers work by utilizing electricity in their operations. As such, you can use a measuring device, called a multimeter, to determine whether certain components are functioning correctly. Most common multimeters enable you to measure current, resistance, or voltage using the same unit. Switching between these functions is accomplished through a button or a dial. The measurements are made through two probes, one colored red for positive (+) and one colored black for negative (-), that are touched on the component that is to be checked. A built-in display shows you the values obtained by the probes.The most common measurement performed is current. Current is measured in Amperes, or amps, and is easily measured. Once you have the multimeter set to amps, simply place the negative probe against the negative contact point. Then, place the positive probe against the positive contact point. If current does not register on the multimeter, then the component is dead and must be replaced.
The second common measurement done on components is voltage. Voltage is measured in volts direct current (Vdc) or in volts alternating current (Vac). The type of voltage being measured determines the placement of the probes. If you are testing for Vdc, ensure that you are connecting the negative probe to the negative side and the positive probe to the positive side. If you are testing for Vac, the connections do not matter much. However, you do not set the multimeter to measure voltage until after you have connected the probes.
The last measurement that you will usually make is resistance, which is measured in ohms (W ). Once the multimeter has been set to measure resistance, place the probes on either end of the component. A current is generated between the probes to test whether or not the component passes current properly. If you get an infinite reading, the component is not allowing electricity to pass from one probe to the other and must be replaced.
Upgrading BIOS
The Basic Input-Output System (BIOS) contains the system settings for the computer, and is stored on a memory chip located on the motherboard. The settings themselves are removed from the BIOS when you turn the computer off, but are restored from the CMOS at boot time. There are two types of BIOS, flash and replace.System BIOS (flash or replace)
Flash BIOS means that the BIOS chip can be reprogrammed with new settings. This type of BIOS requires special software, called a flash program, and a special data file in order to replace the instructions that drive the BIOS. When you need to flash the BIOS, you run the program from a floppy disk that contains the data files.To replace BIOS, you must physically replace the BIOS chip. Follow the procedure outlined in Exercise 1-5.
Exercise 1-5 Replacing BIOS
- Follow the ESD procedures prior to removing the case.
- When the case has been removed, mark and remove any expansion cards or connectors that may be in the way.
- It is at this point that you can use a chip puller to gently remove the chip from its socket.
- To install a BIOS, position the chip over the socket, ensuring that the pins are properly in place, and gently push down on the chip until it is seated.
System Hardware
BIOS settings contain information on the system hardware and must be updated whenever a new component has been added to the computer. To access the BIOS, you must enter the SETUP program when the computer is booting. Some systems use the Del key to enter the program, while others may use an Alt-Esc key combination. To ensure that you hit the appropriate key, carefully watch the computer as it powers up for a message that tells you how to access the SETUP program.System Optimization
Sometimes you are required to optimize a computer system. This basically involves improving the performance of the equipment. While there is only so much you can do, there are various devices that can be optimized, such as memory, hard drives, and cache memory. The following sections describe each in detail.Memory
Optimizing memory usually means that you free up conventional memory, which is the memory address range between 0K and 640K. One of the things you can do to free conventional memory is to load MS-DOS into the High Memory Area (HMA) by adding the following line to the CONFIG.SYS file:DOS = HIGH
Another way to free up conventional memory is to load device drivers or terminate-and-stay resident (TSR) programs into upper memory. TSRs are just programs that remain in memory and do not do anything until a special condition takes place, such as a screen saver program. The first step is to actually check the system memory configuration by using a special program called MEM.EXE with the /C switch. The /C tells the memory program to classify, or individually list the programs that use up memory and what type of memory is being used, as shown in Figure 1-4. In the Conventional column, any number over 0K means that something is using conventional memory.
Modules using memory below 1 MB:
Name Total Conventional Upper Memory
-------- ---------------- ---------------- ------------
MSDOS 17,648 (17K) 17,648 (17K) 0 (0K)
SETVER 848 (1K) 848 (1K) 0 (0K)
HIMEM 1,168 (1K) 1,168 (1K) 0 (0K)
SMS_10X 27,808 (27K) 27,808 (27K) 0 (0K)
IFSHLP 2,864 (3K) 2,864 (3K) 0 (0K)
WIN 3,648 (4K) 3,648 (4K) 0 (0K)
vmm32 3,424 (3K) 3,424 (3K) 0 (0K)
COMMAND 7,504 (7K) 7,504 (7K) 0 (0K)
Free 590,176 (576K) 590,176 (576K) 0 (0K)
Memory Summary:
Type of Memory Total Used Free
---------------- ----------- ----------- -----------
Conventional 655,360 65,184 590,176
Upper 0 0 0
Reserved 393,216 393,216 0
Extended (XMS) 66,060,288 188,416 65,871,872
---------------- ----------- ----------- -----------
Total memory 67,108,864 646,816 66,462,048
Total under 1 MB 655,360 65,184 590,176
Total Expanded (EMS) 66,584,576 (64M)Figure 1-11: Output of the MEM /C Command
Free Expanded (EMS) 16,777,216 (16M)
Largest executable program size 590,160 (576K)
Largest free upper memory block 0 (0K)
MS-DOS is resident in the high memory area.
To move a device driver or TSR to upper memory, you must first load the EMM386.EXE program from the CONFIG.SYS file if it is not already doing so. For device drivers, use a DEVICEHIGH=<drivername> line to load the driver into upper memory. With TSRs, you need to use a LOADHIGH <TSR_name> line instead. The following illustrates the lines needed by the CONFIG.SYS file for both.
DEVICE=C:\DOS\EMM386.EXE
DEVICEHIGH=<drivername>
LOADHIGH <tsr_name>
Hard Drives
Hard drives have a tendency to become fragmented. By fragmented, we are talking about the way in which they store files and file locations. When you save a file to a hard disk, it is not necessarily stored in consecutive areas on the disk. Instead, the drive locates the first areas available and then dumps whatever will fit there, then moves on to the next location and so on until the file is stored. A pointer is used to tell the drive where the next piece of data that constitutes the file is located. When you have an excessive amount of usage on the hard drive, sometimes the pointers become corrupt, or the data itself may be damaged. Also, as the drive has to search in different locations just to retrieve a single file, the speed at which the drive can retrieve the information is slowed down. To defragment the drive, you must run a utility, such as Microsoft’s Defragmenter (DEFRAG.EXE).There are also some software packages on the market that are used to optimize hard drives, such as Norton’s SpeedDisk, which you can purchas at any computer software store.
Cache memory
The only thing that you can do to improve the performance of cache memory is to add more. By adding more cache memory, you enable the computer to store more of the frequently accessed instructions and information.Certification Summary
This chapter has provided you with the knowledge of what each system module does and how it works. This understanding provides you with the insight necessary to proceed with installing, removing, and configuring the various components that are used by a computer system. From there, you covered the various addressing methods and communications aspects of system components. Armed with this knowledge, you should be able to identify unfamiliar devices by the manner in which they connect to the system, as well as by their function. And if that wasn’t enough information, you were presented with system optimization techniques.Two-Minute Drill
| When installing a new power supply, remember that when you reattach the two power connectors to the motherboard, the black wires that are located on each connector must be facing each other. |
| Always wear an electrostatic wrist band to ground yourself when removing the computer’s chassis. |
| Never wear an electrostatic wrist band when working near a monitor, as the build up of static electricity can kill you |
| Every module that makes up a computer system attaches to the motherboard (also called the system board, main board, or planar board) and is able to communicate with other modules through the bus. |
| Electrical power comes in two forms: alternating current (AC), which is the type that comes out of a wall outlet, and direct current (DC), which is the type that your computer uses. |
| The DC current is fed to your computer in one of two forms: ± 5 Vdc and ± 12 Vdc, with the "± " symbol denoting plus or minus. |
| Newer power supplies, known as switching mode power supplies, use transistors in place of older diodes to convert current and are much more efficient at converting power. |
| An overheated power supply will not only fail, but can damage other components inside the computer. |
| Memory, of which there are several types (cache memory, random access memory (RAM), and read only memory (ROM)), is comprised of integrated circuits (ICs) that reside on a chip. |
| Monitors come in a wide variety of types, ranging from the original monochrome display adapter (MDA), which only permitted text-based characters, to today’s high resolution super video graphics adapter (SVGA). Other types are CGA, EGA, and VGA. |
| A modem takes data from the sending computer and translates it from digital to analog signals before transmitting it across a telephone line, a process called modulation. When a modem receives analog signals from a telephone line, it converts the data back into digital signals, a process called demodulation. |
| The Basic Input/Output System, or BIOS, is the mechanism used by your computer to keep track of all this information and still remain independent of the operating system. |
| The CMOS, or Complementary Metal-Oxide Semiconductor (an integrated circuit composed of a metal oxide located directly on the system board) allows the computer to store this information even after the computer has been turned off. |
| The first, and most important, step that you must take before adding or replacing a system module is to power off the computer and disconnect the power cord from the wall outlet. |
| Always note the locations and any connectors that attach to expansion cards before removal to ensure that you will be able to put everything back into its appropriate spot. Make it a habit to mark such things when removing and installing modules. |
| To install memory, place the memory chip over the slot at a 45-degree angle and gently push down on the chip, moving it to an upright position until it clicks into place. |
| Never plug a digital monitor into an analog adapter, or vice versa, as severe damage will result. |
| There are two types of keyboard connectors in use, the DIN-5 connector and the Mini DIN-6 connector. DIN-5s are generally found on AT style keyboards and have a round port with 5 pins. The Mini DIN-6 and also has a round port but differs in that it has 6 pins with one square pin. |
| Devices communicate with the CPU through a special set of lines, called interrupt request lines (IRQs), in the bus. |
| Once the CPU receives an IRQ from a device, it can directly communicate with that device through I/O addresses or I/O ports. |
| Refer back to Table 1-1 and review the standard IRQ settings. |
| Refer back to Table 1-2 and review the more frequently used I/O addresses. |
| Interrupts, I/O addresses, DMA channels, and some additional features have to be configured in the hardware. Jumpers and Dual In-Line Package (DIP) switches are used to accomplish configuration. |
| Cables come in two different forms, shielded cables and unshielded cables. Shielded cables have a wire mesh or Mylar layer added in between the medium and the sheathing that protects the cables from interference. |
| Refer back to Tables 1-3 and 1-4 and memorize the primary control signals for serial and parallel communication. |
| IDE drives can only have up to two drives installed. EIDE drives can have up to four drives installed, but you will only be able to put two drives on a single cable. |
| Small Computer Systems Interface (SCSI) devices permit you to connect multiple devices to one cable, or "chain" them, in configurations of up to 7 to 15 devices on a single cable depending on the SCSI implementation that you are using. |
| Common tools in every computer technician’s toolkit include each variety of screwdriver, a chip puller, and a multimeter. |
| BIOS settings contain information on the system hardware and must be updated whenever a new component has been added to the computer. |
| Flash BIOS means that the BIOS chip can be reprogrammed with new settings. This type of BIOS requires special software, called a flash program, and a special data file in order to replace the instructions that drive the BIOS. |
| One of the things you can do to free conventional memory is to load MS-DOS into the High Memory Area (HMA) by adding a simple line to the CONFIG.SYS file: DOS = HIGH. |
| To defragment a fragmented hard drive, you must run a utility, such as Microsoft’s Defragmenter (DEFRAG.EXE). |
