JAVA LANGUAGE BASIC INFORMATION

Java is uniquely suited for network programming. It provides solutions to many issues that are difficult to solve using other programming languages. Java applets have a higher level of safety than that of similar software packages.

Java makes network programming much easier. Java applications and applet can communicate across the Internet; this feature is especially suitable for large-scale systems that are deployed over a large

geographical area.

Java is portable and platform-independent; Web applications are designed on various hardware and operating environments. Java executes applications in a run-time environment called a virtual machine.

The virtual machine executes the platform-independent bytecode that a Java compiler generates and is easily incorporated into Web browsers or the kernel of the operating system. Java virtual machines and Java API’s (application program interfaces) insulate Java programs from hardware dependencies; this is why Java’s bytecode can run on a wide range of platforms. Java applications can run on a variety of platforms without modification.

Java is also used for database programming. SQLJ is a way to embed the SQL (structured query language) in Java programs and to reduce the development and maintenance costs of Java programs that require database connectivity. SQLJ provides a simple model for Java code containing SQL statements.

SQLJ offers a much simpler and more productive programming API’s than JDBC (Java database connectivity) to develop applications that access relational data, and it can communicate with multi-vendor databases using standard JDBC drivers.

Distributed databases provide a mechanism for the information exchange in distributed processing. A distributed database is different from a centralized database as the latter provides data on one machine.

A distributed database is composed of separate databases distributed on a computer network that are accessed by all permitted users. Information exchange may also occur among databases; in other words, a computer in the distributed database can access the data stored in other computers.

Data consistency is guaranteed by intrinsic properties of databases. One advantage of a distributed database is that local databases are used to store the local information in the system.

Compared with a centralized database, a distributed database can save capital investments in communication networks with a higher security and reliability, since it can restrict local faults within the corresponding subareas.

DESIGNING COUNTERS WITH ARBITRARY SEQUENCES BASICS

So far we have discussed different types of synchronous and asynchronous counters. A large variety of synchronous and asynchronous counters are available in IC form, and some of these have been mentioned and discussed in the previous sections.

The counters discussed hitherto count in either the normal binary sequence with a modulus of 2N or with slightly altered binary sequences where one or more of the states are skipped. The latter type of counter has a modulus of less than 2N , N being the number of flip-flops used.

Nevertheless, even these counters have a sequence that is either upwards or downwards and not arbitrary. There are applications where a counter is required to follow a sequence that is arbitrary and not binary.

As an example, an MOD-10 counter may be required to follow the sequence 0000, 0010, 0101, 0001, 0111, 0011, 0100, 1010, 1000, 1111, 0000, 0010 and so on. In such cases, the simple and seemingly obvious feedback arrangement with a single NAND gate discussed in the earlier sections of this chapter for designing counters with a modulus of less than 2N cannot be used.

There are several techniques for designing counters that follow a given arbitrary sequence. In the present section, we will discuss in detail a commonly used technique for designing synchronous counters using J-K flip-flops or D flip-flops.

The design of the counters basically involves designing a suitable combinational logic circuit that takes its inputs from the normal and complemented outputs of the flip-flops used and decodes the different states of the counter to generate the correct logic states for the inputs of the flip-flops such as J, K, D, etc.

But before we illustrate the design procedure with the help of an example, we will explain what we mean by the excitation table of a flip-flop and the state transition diagram of a counter. An excitation table in fact can be drawn for any sequential logic circuit, but, once we understand what it is in the case of a flip-flop, which is the basic building block of sequential logic, it would be much easier for us to draw the same for more complex sequential circuits such as counters, etc.

MAGNETIC HARD DISK BASIC INFORMATION AND TUTORIALS

Hard disks are nonvolatile random access secondary data storage devices, i.e. the desired data item can be accessed directly without actually going through or referring to other data items. They store the data on the magnetic surface of hard disk platters.

Platters are made of aluminium alloy or a mixture of glass and ceramic covered with a magnetic coating. Figure 15.32 shows the internal structure of a typical hard disk. As can be seen from the figure, there are a few (two or more) platters stacked on top of each other on a common shaft.

The shaft rotates these platters at speeds of several thousand rpm. Each platter is organized into tracks and sectors (Fig. 15.33), both having a physical address used by the operating system to look for the stored data.

Tracks are concentric circles used to store data. Each track is further subdivided into sectors so that the total numbers of sectors per side of the magnetic disk are the product of the number of tracks per side and the number of sectors per track.

And if it is a double-sided disk, the total number of sectors gets further multiplied by 2. From known values of the total number of sectors and the number of bytes stored per sector, the storage capacity of the disk in bytes can then be computed.

There is a read/write head on one or both sides of the disk, depending upon whether it is a single sided or a double-sided disk. The head does not physically touch the disk surface; it floats over the surface and is close enough to detect the magnetized data.

The direction or polarization of the magnetic domains on the disk surface is controlled by the direction of the magnetic field produced by the write head according to the direction of the current pulse in the winding. This magnetizes a small spot on the disk surface in the direction of the magnetic field.

A magnetized spot of one polarity represents a binary ‘1’, and that of the other polarity represents a binary ‘0’. One of the most important parameters defining the performance of the hard disk is the size of the disk.

Disks are available in various sizes ranging from 20 GB to as large as 80 GB. Other parameters defining the hard disk performance include seek time and latency time. Seek time is defined as the average time required by the read/write head to move to the desired track.

Latency time is defined as the time taken by the desired sector to spin under the head once the head is positioned over the desired track.

INTERNAL BUS OF COMPUTERS BASIC INFORMATION

Input/output ports are used to connect the computer to external devices. Input and output standards described in the previous sections are referred to as external bus standards.

In addition to these external buses, computers also have internal buses that carry address, data and control signals between the CPU, cache memory, SRAM, DRAM, disk drives, expansion slots and other internal devices. Internal buses are of three types, namely the local bus, the PCI bus and the ISA bus.

Local Bus

This bus connects the microprocessor to the cache memory, main memory, coprocessor and PCI bus controller. It includes the data bus, the address bus and the control bus.

It is also referred to as the primary bus. This bus has high throughput rates, which is not possible with buses using expansion slots.

PCI Bus

The peripheral control interconnect (PCI) bus is used for interfacing the microprocessor with external devices such as hard disks, sound cards, etc., via expansion slots. It has a VESA local bus as the standard expansion bus.

Variants of the PCI bus include PCI 2.2, PCI 2.3, PCI 3.0, PCI-X, PCI-X 2.0, Mini PCI, Cardbus, Compact PCI and PC/104-Plus. The PCI bus will be superseded by the PCI Express bus. PCI originally had 32 bits and operated at 33 MHz. Various variants have different bits and data transfer rates.

ISA Bus

The industry-standard architecture (ISA) bus is a computer standard bus for IBM-compatible computers. It is available in eight-bit and 16-bit versions.

The VESA local bus was designed to solve the bandwidth problem of the ISA bus. It worked alongside the ISA bus where it acted as a high-speed conduit for memory-mapped I/O and DMA, while the ISA bus handled interrupts and port-mapped I/O.

Both these buses have been replaced by the PCI bus.

LAN CONNECTIVITY BASIC INFORMATION AND TUTORIALS

The migration of LAN cabling infrastructure to the use of twisted pair cable has been accompanied by a significant increase in the use of the modular RJ-45 connector. Today most network adapter cards, hubs and concentrators are manufactured to accept the use of the RJ-45 connector.

One of the first networks to use the RJ-45 connector was 10BASE-T, which represents a 10 Mbps version of Ethernet designed for operation over unshielded twisted pair (UTP). Since UTP cable previously installed in commercial buildings commonly contains either three or four wire pairs, the RJ 45 connector or jack was selected to be used with 10BASE-T, even through this version of Ethernet only supports the use of four pins.

Although 10BASE-T only uses four of the eight RJ-45 pins, other versions of Ethernet and different LANs use the additional pins in the connector. For example, a full duplex version of Ethernet requires the use of eight pins.

Thus, the original selection of the RJ-45 connector has proven to be a wise choice. Ethernet is a termthat actually references a series of local area networks that use the same access protocol (CSMA/CD) but can use different types of cable.

Early versions of Ethernet operated over either thick or thin coaxial cable. The attachment of an Ethernet workstation to a thick coaxial cable is accomplished through the use of a short cable which connects the workstation to a device known as a transceiver. This connection is accomplished through the use of a DB-15 connector.

The attachment of an Ethernet workstation to a thin coaxial cable requires the use of a T connector on the coax. The T connector is then cabled to a BNC connector on the network adapter card installed in the workstation.

Recognizing the fact that a workstation could be connected to a thick or thin coaxial cable or a twisted-pair based network manufacturers would have to support three separate types of adapter cards based upon different connectors required.

Rather than face this inventory nightmare, most Ethernet network adapter card manufacturers now incorporate all three connectors on the cards they produce. Not only does this type of card simplify the manufacturer’s inventory but, in addition, it provides end-users with the ability to easily migrate from one wiring infrastructure to another without having to replace network interface cards.

COMPUTER PRINTER AND DISPLAY TERMINALS BASIC INFORMATION

A serial or character printer, whose name resulted from the fact that they print one character at a time, was the display mechanism first used with terminals. The first serial printers were ‘fully formed’ impact printers in which different types of mechanisms, including a daisy wheel, type-ball or rotating cylinder which formed characters from a single piece of type, were used to strike a ribbon to produce a printed image.

The editing capability provided by the terminal was minimal, typically permitting the operator to delete a previously entered character or the current line, since the terminal transmitted and received data on a line by line basis. A second type of impact printer which grew in popularity during the 1970s and 1980s to where it has virtually replaced fully formed printers is the dot matrix printer.

The dot matrix printer employs a matrix of pins in its print head. The first dot matrix printers used a rectangular matrix of dots, typically 7 dots high by 5 dots wide or 9 dots high by 7 dots wide. The pins in the matrix are selectively ‘fired’ to form each character. Printing of characters results from the movement of the print head containing a column of 7 or 9 pins across the paper, with the printer selectively firing the pins at 5 or 7 successive intervals to form each character.

Until the mid-1980s, the matrix of pins used to form characters resulted in a considerable amount of white space between dots. This space made the dot matrix pattern easily discernible to the eye and limited the use of printed output produced by this type of printer to draft correspondence.

By the mid 1980s, advances in print head technology resulted in the inclusion of more pins on some print heads. The additional pins were used to considerably reduce the space between pin impacts in forming a character.

Other dot matrix developments included two-pass printing in which the first pass of printing a line was followed by the printer feeding the paper upward by a slight amount, perhaps 1/256th of an inch, prior to the line being printed a second time.

One result of placing more pins on the print head and using a two-pass printing technique was. a higher quality print. Since this print resembled the letter quality print of a full impact printer, it became known as near letter quality (NLQ).

The firing of additional pins to form a better print image required additional time, resulting in NLQ printing being slower than conventional dot matrix printing. Thus, most modern dot matrix printers have two or more user selectable print modes – draft and NLQ – with the draft print mode providing

a considerably faster print rate than the NLQ print mode.

A second major category of printers employs non-impact technology to form characters. Non-impact printers include thermal matrix ink jet and laser devices. The thermal matrix printer forms characters by applying a voltage to pins in a matrix, causing the pins to be heated. The heated pins interact with heat-sensitive paper used in these printers, resulting in the formation of characters.

The ink jet printer has a nozzle consisting of a matrix of holes out of which ink is squirted to form characters. Thus, both thermal matrix and ink jet printers are based upon dot matrix technology. In comparison, the laser printer uses a rotating drum and a small amount of current to generate a magnetic field, which results in toner from a cartridge adhering to distinct locations on paper passing around the drum. Laser printers have resolutions between 300 and 1200 dots per inch (dpi) and through software can form characters in almost any shape.

The key limitation associated with the use of printers for both input and output is the elementary editing capability provided by this type of terminal device. Data entered from the keyboard are either printed and transmitted as each character is pressed or stored in a buffer area.

The buffer storage area contained in most ASR and KSR terminals is only capable of holding one line of data or 72 to 80 characters depending upon the type of terminal. By using the backspace key to eliminate a previously entered character, an operator can perform elementary editing.

Once the carriage return key has been pressed, however, the entire line is transmitted, resulting in an operator having to re-enter the line with any changes he or she desires to correct a previously entered line. As an alternative to the use of the backspace key, an operator can simultaneously press the control (Ctrl) key and an alphabetic key, canceling the present line and removing its contents from buffer storage. This action causes a carriage return and line feed to be automatically generated, permitting the operator to begin his or her data entry anew.

NETWORK INTERFACE CARDS BASIC INFORMATION AND TUTORIALS

A network interface card (NIC), which is also commonly referred to as a network adapter card, is normally installed in the system unit of a personal computer and provides an interface between the computer on the media in the form of a LAN cable.

In addition to providing a physical interface to the LAN, the adapter card contains instructions, usually in the form of read only memory, which perform network access control functions, as well as the framing of data for transmission onto the network and the removal of framing from data received from the network.

To illustrate an example of access control performed by a network adapter, let us assume that the LAN is contention-based. Then, the adapter card will ‘listen’ to the LAN prior to attempting to transmit data.

If no activity is heard on the LAN the adapter card will transmit data onto the media, whereas the presence of activity will result in the adapter deferring transmission and returning to a listening state.

One of the problems associated with an access methodology based upon contention is the fact that two or more workstations that listen and have data to transmit will do so.

As you might expect, this will result in the collision of data, and a network adapter which supports a contention access scheme will contain collision detection circuitry.

Then, once a collision has been detected each adapter card will employ circuitry which results in the generation of a random time interval to be used prior to attempting to retransmit.

This method of LAN access is referred to as Carrier Sense Multiple Access with Collision Detection (CSMA/CD) and represents the access method used on Ethernet LANs. 

COMPUTER CONNECTION TERMINALS BASIC INFORMATION

Terminals were originally categorized as interactive or remote batch, the latter also commonly referred to as a remote job entry device. An interactive terminal is typically used to transmit relatively short queries or to provide an operator with the ability to respond to computer-generated screen displays by entering data into defined fields prior to transmitting the filled in screen.

Once the data have been received, the destination device will respond to the transmission in a relatively short period of time, typically measured in seconds. In comparison, remote batch terminals provide the operator with the ability to group or batch a series of jobs that can range in scope from programs developed for execution on a large computer to queries that are also structured for execution against a database maintained on a large computer system.

The introduction of the personal computer altered the previous distinction. That is, the ability to use the hard drive of a PC as a storage mechanism enables the personal computer to transmit and receive files that can range up to a gigabyte or more in size.

Although the distinction between interactive and batch terminals was essentially eliminated by the PC, it is an important topic to note as many software programs were developed to turn a personal computer into a specific type of terminal by emulating the features of a terminal. As you might expect, such software is referred to as terminal emulation software.

Interactive terminal classification

One method commonly used to classify interactive terminals is based on their. This method of terminal classification has its origins with tletype terminals in which those terminals could be configured as a receive only (RO), keyboard send–receive (KSR) or automatic send–receive (ASR) device.

Receive only (RO)

A receive only (RO) terminal consists of a stand-alone printer with a serial communications interface but lacking a keyboard. Originally developed to simply receive messages transmitted on message switching systems developed in the 1930s, a limited number of RO terminals are still in use today.

Keyboard send-receive (KSR)

Originally, keyboard send–receive (KSR) terminals included a printer, serial communications interface, and keyboard. This permitted the terminal operator to both originate a message from the keyboard as well as to print a received message.

Automatic send-receive (ASR)

The third interactive terminal classification is automatic send–receive (ASR). An ASR terminal consists of a printer, serial communications interface, keyboard and auxiliary storage. Here the auxiliary storage permits messages to be composed ‘off-line’ with the terminal not attached via a communications facility to its intended transmission destination.

INTEGRATED SERVICES DIGITAL NETWORK (ISDN) BASIC INFORMATION

The integrated services digital network (ISDN) concept is designed to allow voice and data to be sent in the same way along the same lines. Currently, most subscribers are connected to the switched telephone network by local loops and interface cards designed for analog signals. This is reasonably well-suited to voice communication, but data can be accommodated only by the use of modems.

As the telephone network gradually goes digital, it seems logical to send data directly over telephone lines without modems. If the local loop could be made digital, with the codec installed in the telephone instrument, there is no reason why the 64 kb/s data rate required for PCM voice could not also be used for data, at the user’s discretion.

The integrated services digital network concept provides a way to standardize the above idea. The standard encompasses two types of connections to the network. Large users connect at a primary-access point with a data rate of 1.544 Mb/s. This, you will recall, is the same rate as for the DS-1 signal described earlier. It includes 24 channels with a data rate of 64 kb/s each.

One of these channels is the D (data) channel and is used for commonchannel signaling, that is, for setting up and monitoring calls. The other 23 channels are called B (bearer) channels and can be used for voice or data, or combined, to handle high-speed data or digitized video signals, for example.

Individual terminals connect to the network through a basic interface at the basic access rate of 192 kb/s. Individual terminals in a large organization use the basic access rate to communicate with a private branch exchange (PBX), a small switch dedicated to that organization.

Residences and small businesses connect directly to the central office by way of a digital local loop. Two twisted pairs can be used for this, though more use of fiber optics is expected in the future.

Basic-interface users have two 64 kb/s B channels for voice or data, one 16 kb/s D channel, and 48 kb/s for network overhead. The D channel is used to set up and monitor calls and can also be employed for low-data-rate applications such as remote meter-reading.

All channels are carried on one physical line, using time-division multiplexing. Two pairs are used, one for signals in each direction.

Implementation of the ISDN has been slow, leading some telecommunications people to claim, tongue-in-cheek, that the abbreviation means “it still does nothing.” Several reasons can be advanced for this.

First, converting local loops to digital technology is expensive, and it is questionable whether the results justify the cost for most small users. Residential telephone users would not notice the difference (except that they would have to replace all their telephones or buy terminal adapters), and analog lines with low-cost modems or fax machines are quite satisfactory for occasional data users.

Newer techniques like Asymmetrical Digital Subscriber Line (ADSL), which is described in the next section, and modems using cable-television cable have higher data rates and are more attractive for residential and small-office data communication.

Very large data users often need a data rate well in excess of the primary interface rate for ISDN. They are already using other types of networks. It appears possible that the ISDN standard is becoming obsolete before it can be fully implemented.

With this in mind, work has already begun on a revised and improved version of ISDN called broadband ISDN (B-ISDN). The idea is to use much larger bandwidths and higher data rates, so that high-speed data and video can be transmitted. B-ISDN uses data rates of 100 to 600 Mb/s.

EMAIL SPAM WARNING AND SECURITY BASIC INFORMATION AND TUTORIALS

HOW TO PROTECT YOURSELF FROM VIRUS AND SCRIPTS?

E-mail is the giant hole in your home or business through which almost all worms, viruses, Trojan horse files, general malware, and, of course, spam pour.

Spam and malware go hand in hand.

When users open file attachments from e-mail without checking the file for a virus first, they run the risk of infection. Yes, I know that you shouldn’t blame the victim and that the virus writers are to blame often fail to teach users to protect themselves. Users who open attachments from people they don’t know pay the price.

Making the situation worse, many viruses spread by sending e-mails (with infected attachment) to every address in the infected machine’s Microsoft Outlook or Outlook Express address book database. So trusting users who may never open an e-mail from an unknown person open e-mails from someone they do know.

Bam! They’re infected, because the e-mail really wasn’t from someone they know; it came from the virus stealing the addresses from someone they know.


Be careful

E-mail (and spam) senders trick you into loading a virus in the following ways:
✦ Pretend to be from someone you know and trust
✦ Hide the fact that an attachment is executable
✦ Offer help handling virus infections
✦ Include HTML code to activate programs located on Web sites


When you get an attachment you don’t expect, verify the sender and ask that person about the file you received. If the person sent it on purpose, you’ll have no problem. If that person has no idea that an e-mail with an attachment came bearing their address, both of you need to disinfect your systems.

Don’t open attachments if they are executable files. You can tell this by checking their file extension (the letters to the right of the dot at the end of the file name).

Unless you are positive the sender and files are trustworthy, do not click the attached files. Files with the following extensions can cause problems by executing when you open them:

.bat
.com
.exe
.pif
.reg
.vb
.vbs

When you look at the files on your computer, you will notice many of your files have these extensions and the files are trustworthy. Your operating system and all your applications rely on these file types. However, when you click an unexpected file in an e-mail message, the application will begin working so quickly your system will be compromised before you can react.

MICROCOMPUTER BASIC INFORMATION AND TUTORIALS

The basic components of a microcomputer system are:

A central processing unit (CPU).

A memory, comprising both ‘read/write’ and ‘read-only’ devices (commonly called RAM and ROM respectively).

A mass storage device for programs andjor data (e.g. a floppy and/or hard disk drive).

A means of providing user input and output (via a keyboard and display interface).

Interface circuits for external input and output (I/O). These circuits (commonly called ‘ports’) simplify the connection of peripheral devices such as printers, modems, mice, and joysticks.

In a microcomputer (as distinct from a mini or mainframe machine) the functions of the CPU are provided by a single VLSI microprocessor chip (e.g. an Intel 8086, 8088, 80286, 80386, 80486, or Pentium). The microprocessor is crucial to the overall performance of the system.

Indeed, successive generations of PC are normally categorized by reference to the type of chip used. The ‘original’ PC used an 8088, AT systems are based on an 80286, ’386 machines use an 80386, and\ so on.

Semiconductor devices are also used for the fast redd/write and readonly memory. Strictly speaking, both types of memory permit ‘random access’ since any item of data can be retrieved with equal ease regardless of its actual location within the memory.

Despite this, the term ‘RAM’ has become synonymous with semiconductor read/write memory. (VLSI means very large scale integration, i.e. a complex chip.) The semiconductor ROM provides non-volatile storage for part of the operating system code (this ‘BIOS’ code remains intact when the power supply is disconnected).

The semiconductor RAM provides storage for the remainder of the operating system code (the ‘DOS’), applications programs and transient data (including that which corresponds to the screen display).

It is important to note that any program or data stored in RAM will be lost when the power supply is\ switched off or disconnected. The only exception to this is a small amount of ‘CMOS memory’ kept alive by means of a battery.

This ‘battery-backed’ memory is used to retain important configuration data, such as the type of hard and floppy disk fitted to the system and the amount of RAM present.

TIP

It is well worth noting down the contents of the CMOS memory to avoid the frustration of having to puzzle out the settings for your own particular system when the backup battery eventually fails and has to be replaced. To view the current CMOS configuration settings press the ‘Del’ key during the bootup sequence and enter the ‘Setup‘ routine.

COMPUTER HARDWARE FAULT TROUBLESHOOTING TUTORIALS

Hardware faults are generally attributable to component malfunction or component failure. Electronic components do not generally wear out with age but they become less reliable at the end of their normal service life.

It is very important to realize that component reliability is greatly reduced when components are operated at, or near, their maximum ratings. As an example, a capacitor rated at 25V and operated at 1OV at a temperature of 20°C will exhibit a mean-time-to-failure (MTTF) of around 200000 hours.

When operated at 40°C with 20V applied, however, its MTTF will be reduced by a factor of 10 to about 20 000 hours.

TIP: The mean-time-to-failure (MlTF) of a system can be greatly extended by simply keeping it cool. Always ensure that your PC is kept out of direct sunlight and away from other heat producing sources (such as radiators). Ventilation slots should be kept clear of obstructions and there must be adequate air flow all around the system enclosure. For this reason it is important to avoid placing tower systems under desks, in corners, or sandwiched between shelves.

Hardware fault, what to do

If you think you have a hardware fault, the following stages are typical:

1. Perform functional tests and observatioos. If the fault has been reported by someone else, it is important to obtain all relevant information and not make any assumptions which may lead you

along a blind alley.

2. Eliminate functional parts of the system from your investigation.

3. Isolate the problem to a particular area of the system. This will often involve associating the fault with one or more of the following:

(a) power supply (including mains cable and fuse)

(b) system motherboard (includes CPU, ROM and RAM)

(c) graphics adapter (includes video RAM)

(d) disk adapter (includes disk controller)

(e) other IjO adapter cards (e.g. serial communications cards,

modem cards, USB devices, SCSI devices, etc.)

(f) floppy disk drive (including disk drive cables and connectors)

(g) hard disk drive (including disk drive cables and connectors)

(h) keyboard and mouse

(i) display adapter

(j) monitor

(k) external hardware (such as a printer sharer or external drive)

(I) communications or network problems

4. Disassemble (as necessary) and investigate individual components and subsystems (e.g. carry out RAM diagnostics, gain access to system board, remove suspect RAM).

5. Identify and replace faulty components (e.g. check RAM and replace with functional component).

6. Perform appropriate functional tests (e.g. rerun RAM diagnostics, check memory is fully operational).

7. Reassemble system and, if appropriate, ‘soak test’ or ‘burn in’ for an appropriate period.

TIP: If you have more than one system available, items such as the system unit, display, keyboard, and external cables can all be checked (and eliminated from further investigation) without having to remove or dismantle anything. Simply disconnect the suspect part and substitute the equivalent part from an identical or compatible system which is known to be functional.

TROUBLE SHOOTING THE PCI BUS BASIC INFORMATION AND TUTORIALS

Trouble with PCI devices can be caused by
Software bugs.
Software settings.
Hardware faults.
Device conflicts.

The standard way to fix software bugs is to obtain the latest card driver from the manufacturer. This can usually be achieved via the manufacturers’ website. These websites often contain details of hardware or software conflicts.


Some boards will not work if they are present in the same machine as other devices. An example of this occurred in the PC of one of the authors. It was fitted with a PCI SCSI card that allowed a SCSI scanner to work very well.

All was well until the scanner and its SCSI cable were removed. After this, the IDE CD-ROM drive eject button caused the system to reboot. Removing the now unused PCI SCSI card failed to resolve the problem.

It had to be reinserted, the driver removed via the Windows 98 Control Panel and the card removed again before a reboot caused the ‘new hardware found’ dialogue. Problems with seemingly unrelated devices are not uncommon. This problem was discovered via the Microsoft knowledge base website.


Only after trying to resolve software/hardware conflicts should a hardware fault be suspected. If a card is suspected of giving trouble, shut down the system, remove the card and install it in a second PC. If the trouble persists in the second PC, the card is probably faulty - repair is not usually economic.

Without specialist equipment, troubleshooting the PCI can be tricky. Test equipment such as the PCI diagnostics card from UltraX Inc. (www.uxd.com/phdpci.shtmlw) ill test the PCI bus when other devices are dead or missing.


TIP: If you need to upgrade a device driver, it is often better to uninstall the old one first. Reinstallation sometimes retains old (and possibly faulty) software components such as .DLL files.

PCI BUS DEFINITION BASIC INFORMATION AND TUTORIALS

Initially devised by Intel and subsequently supported by the PCI Special Interest Group (PCI-SIG), the Peripheral Component Interconnect bus has become established as arguably the most popular and ‘future proof bus standard available today. It avoids the IRQ conflicts of the ISA bus by using plug and play.

With plug and play, the system configures itself by allowing the PCI BIOS to access configuration registers on each add-in board at bootup time. As these configuration registers tell the system what resources they need (I/O space, memory space, interrupts, etc.), the system can allocate its resources accordingly, making sure that no two devices conflict.

The PCI BIOS cannot directly query ISA devices to determine which resources they need. This can sometimes give rise to problems in systems using both ISA and PCI. A PCI board’s 1/0 address and interrupt are not fixed, and can change every time the system boots.

PCI offers flexible bus mastering. This means that any PCI device can take control of the bus at any time, allowing it to shut out the CPU. Devices use bandwidth as available, even all the bandwidth, if no other demands are made for it.

Bus mastering works by sending request signals when a device wants control of the bus and the requestbeing
granted if data traffic allows it.

Because the PCI bus is not connected directly to the CPU (it is separated by an interface formed by a dedicated ‘PCI chipset’) the bus is sometimes referred to as a ‘mezzanine bus’. This technique offers two advantages over the earlier VL bus specification:

I. Reduced loading of the bus lines on the CPU (permitting a longer data path and allowing more bus cards to be connected to it).

II. Making the bus ‘processor independent’.

The original PCI bus was designed for operation at clock speeds of 33MHz. With a 32-bit data path, the 33MHz clock rate implies a maximum data transfer rate of around 130Mbyte/s (about the same as VL bus). Like the VL bus, the PCI bus connector is similar to that used for MCA. To cater for both 32- and 64-bit operation, PCI bus cards may have either 62 or 94 pins.

Later PCI implementations had a bus clock rate up to 66 MHz, giving up to 132 MB per second transfer rate over the 32-bit bus.

TROUBLE SHOOTING THE MOTHER BOARD OF A COMPUTER BASIC INFORMATION AND TUTORIALS

Most motherboard problems are related to cabling and connections. Ensure all cables are connected firmly. Ribbon cables and power cables can often come loose.

Ensure all ‘plugin’ items such as the CPU, RAM modules and adapters such as video cards, modems, etc. are inserted correctly. Contacts can become oxidized or dirty: as a quick fix, remove and reinsert the item several times to wear away the oxide.

This is not a long-term solution, the parts should be removed and cleaned with a good quality contact cleaner.

Other problems are often related to specific hardware but check the items below first.

-Remove all add-on cards except the graphics adapter and start the machine. If that fails to give a running machine, check connections, settings, CPU and RAM compatibility, etc. in the motherboard technical specification.

Keep the PC speaker connected but not any external speakers. Reset the BIOS settings to their default values. On some boards there is a jumper or other way to clear the BIOS settings.

-Is there sufficient power from the power supply?

-Try a different keyboard.

-Check for bent pins on the board. You might be lucky if you try to

-Try disabling the cache in the BIOS. If this makes the machine work, straighten them. If not, you will need to buy a new board!

REPLACING AND UPGRADING THE CPU BASIC INFORMATION AND TUTORIALS

Replacing the CPU
The processor chip (regardless of type) is invariably fitted in a socket or a slot and this makes removal and replacement quite straightforward provided that you take reasonable precautions.

The following describes the stages in removing and replacing a CPU chip:

1. Switch 'off, disconnect from the supply and gain access to the system board.

2. Ensure that you observe the safety and static precautions at all times. Have some anti-static packing available to receive the CPU when it has been removed.

3. Locate the CPU and ensure that there is sufficient room to work all around it (you may have to move ribbon cables or adapter cards to gain sufficient clearance to use the extraction and insertion tools).


4. Depending on the design of the socket/slot, release the catch that holds the CPU in place.

5. Immediately deposit the chip in an anti-static container (do not touch any of the pins).

6. Pick up the replacement chip from its anti-static packing. Position the insertion chip over the socket and ensure that it is correctly orientated.

7. Reassemble the system (replacing any adapter cards and cables that may have been removed in order to gain access or clearance around the CPU). Reconnect the system and test.


Upgrading the CPU
A relentless increase in the power of the CPU makes this particular component a prime candidate for upgrading a system in order to keep pace with improvements in technology.

Moore’s law says that the number of transistors used in microprocessors will double every 18 months. The progress seems to correlate well with this ‘law’.

Although Moore’s law refers to the number of transistors in an integrated circuit, the clock speed of Intel processors seems to conform quite well with the ‘law’.


TIP: Before attempting a CPU upgrade it is well worth giving careful attention to the cost effectiveness of the upgrade - in many cases there may be other ways of improving its performance for less outlay. In particular, if you are operating on a limited budget it may be worth considering a RAM or hard disk upgrade before attempting to upgrade the CPU. In both cases, significant improvements in performance can usually be achieved at moderate cost.

BIOS (BASIC INPUT OUTPUT SYSTEM) OF COMPUTERS BASIC INFORMATION AND TUTORIALS

What is BIOS?


All motherboards include a small block of Read Only Memory (ROM) which is separate from the main system memory used for loading and running software. The ROM contains the PC’s BIOS and this offers two advantages.

The code and data in the ROM BIOS need not be reloaded each time the computer is started, and they cannot be corrupted by wayward applications that write into the wrong part of memory. A flash-upgradeable BIOS may be updated via a floppy diskette to ensure future compatibility with new chips, add-on cards etc.

The BIOS is comprised of several separate routines serving different functions. The first part runs as soon as the machine is powered on. It inspects the computer to determine what hardware is fitted.

Then it conducts some simple tests to check that everything is functioning normally—a process called the power-on self-test. If any of the peripherals are plug-and-play devices, the BIOS assigns the resources. There’s also an option to enter the Setup program.

This allows the user to tell the PC what hardware is fitted, but thanks to automatic self-configuring BIOS, this is not used so much now.

If all the tests are passed, the ROM tries to boot the machine from the hard disk. Failing that, it will try the CD-ROM drive and then the floppy drive, finally displaying a message that it needs a system disk. Once the machine has booted, the BIOS presents DOS with a standardized API for the PC hardware. In the days before Windows, this was a vital function. But 32-bit “protect mode” software doesn’t use the BIOS, so it is of less benefit today.

Most PCs ship with the BIOS set to check for the presence of an operating system in the floppy disk drive first, then on the primary hard disk drive. Any modern BIOS will allow the floppy drive to be moved down the list so as to reduce normal boot time by a few seconds.

To accommodate PCs that ship with a bootable CD-ROM, most BIOS allow the CD-ROM drive to be assigned as the boot drive. BIOS may also allow booting from a hard disk drive other than the primary IDE drive. In this case, it would be possible to have different operating systems or separate instances of the same OS on different drives.


Windows 98 (and later) provides multiple display support. Since most PCs have only a single AGP slot, users wishing to take advantage of this will generally install a second graphics card in a PCI slot. In such cases, most BIOS will treat the PCI card as the main graphics card by default.

However, some allow either the AGP card or the PCI card to be designated as the primary graphics card. While the PCI interface has helped by allowing IRQs to be shared more easily, the limited number of IRQ settings available to a PC remains a problem for many users.

For this reason, most BIOS allow ports that are not in use to be disabled. It will often be possible to get by without needing either a serial or a parallel port because of the increasing popularity of cable and ADSL Internet connections and the ever-increasing availability of peripherals that use the USB interface.

PROGRAMMABLE READ-ONLY MEMORY (PROM) BASIC INFORMATION

Fusible link PROM has now largely been superseded by ultraviolet erasable programmable read-only memory (UVEPROM) and electrically erasable programmable read-only memory (EEPROM). While fusible link devices are effectively permanent, UVEPROM and EEPROM have expected data retention times of 10 to 40 years at room temperature; this has implications for system reliability so they may not be suitable for some systems like those that are exposed to very high temperatures or radiation, such as satellites.

UVPROM and EEPROM use floating gate FETs as the programmable elements. These operate like a normal FET except the gate structure contains an extra isolated conducting layer, the floating gate, which forms a capacitor that can be charged by application of a much higher voltage than used for normal operation.

The effect of charging the capacitor is to change the threshold voltage of the FET. In the uncharged state, the floating gate prevents the FET from turning on when the row line is pulled high, and does not pull the column line low. Once the floating gate is charged the FET can be turned on, pulling the column line low. FLASH memory is based on similar physical effects but the logical architecture is different.

The charge will remain on the capacitor until it leaks away over time, taking 10 to 40 years at room temperature; this leakage can be accelerated by exposure to ultraviolet (UV) light or a high voltage. UVEPROMs are designed to be erased by exposure to short-wavelength UV radiation for about 20 minutes.

It should be noted that the device will be erased by leaving it in direct sunlight for a few days, or under bright fluorescent light for a few months to a year. The package has a quartz window (Figure 10.2) to allow the light in, and this should be covered with a lightproof label if the device is likely to be exposed.

UVEPROMs are available without the window in the package, and these devices are referred to as one time programmable (OTP) devices. The silicon die is identical to that used in the windowed part but the cost of the package is lower.

Microcontrollers are often provided in UVEPROM for development work and in OTP for production. EEPROM do not need the window because they have additional circuitry to erase/re-write the bits.

Fusible link memories are permanent and they can not be reprogrammed, although it is sometimes possible to design a program arrangement so that sections of program can be bypassed by blowing more fuses. The reason that the no-operation (NOP) instruction of some older microprocessors is FFH is to allow changes to programmable devices that cannot be erased.

An instruction can be changed to NOP by blowing all the unblown fuses of a byte. Modern microcontrollers often use 00H as the NOP instruction for the same reason, since OTP versions of UVEPROMs allow program code to be deleted by programming all the bits of a byte.

Small-memory devices of up to about 256 bytes could be made in a similar way to the 8-byte example shown in Figure 10.1, however, as memory devices get larger the address decoding overhead becomes an issue. Square arrays of memory cells are more efficient in their use of silicon.

Using 8 square arrays, one for each bit of the byte, reduces the decoding requirement from 4096 row drivers to 512 row drivers and 512 column lines, making the whole device smaller and nearer a square in shape which makes layout of the row and column interconnect easier.