|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|
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± 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.
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.
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.
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.
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.
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.
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
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.
FirmwareFirmware 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.
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.
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.
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.
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.
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.
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
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
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.
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
Click Here To View Figure 1-6: Installing a CD-ROM drive
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.
To install a modem, you merely reverse the procedures for removing it.
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.
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.
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.
|IRQ Number||Standard Device Assignment|
|NMI (nonmaskable interrupt)||Memory parity error|
|2||Cascaded to IRQ 9|
|3||Serial port (COM2)|
|4||Serial port (COM1)|
|5||Parallel port (LPT2)|
|7||Parallel port (LPT1)|
|9||Redirected as IRQ2|
|14||Hard disk controller|
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|
|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|
|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.
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.
Click Here To View Figure 1-7: Jumpers
Click Here To View Figure 1-8: Seating an adapter card
Figure 1-9: Common cable types
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.
|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 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.
|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.
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.
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.
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.
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.
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.
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.
|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|
|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|
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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)
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.
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.
|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).|