1. Maintenance of Computer System
Electronics & Communication Engineering Deptt
Seth Jai parkash Polytechnic Damla

2. Computer Hardware Maintenance Outline:
Introduction to computer hardwares
Basic operations
Motherboard
Processor
RAM & ROM
Ports & Cabling
Connectors & Expansion Card
Storage & Hard Drives
Power Supply
Types of printers

3. Graphic Representation of Computer Components:

4. Motherboard
The motherboard is the main circuit board of a microcomputer. It contains the central processing unit (CPU), the Basic Input/Output System (BIOS), memory, mass storage interfaces, serial and parallel ports, expansion slots, and all the controllers for standard peripheral devices like the keyboard, disk drive and display screen.
BIOS stands for Basic Input/Output System. It is the lowest-level software in the computer; it acts as an interface between the hardware (especially the chipset and processor) and the operating system. The BIOS provides access to the system hardware and enables the creation of the higher-level operating systems that you use to run your applications.
The BIOS is also responsible for allowing you to control your computer's hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.

5. ATX MOTHERBOARD
ATX

6. Further research: Buses, System Bus, Expansion Bus
Inside the Processor
The CPU has 2 fundamental sections: the Control Unit, and the Arithmetic Logic Unit. These work together to perform processing operations.
Fundamentally all processors do the same thing. They take signals in the form of 0s and 1s (thus binary signals), manipulate them according to a set of instructions, and produce output in the form of 0s and 1s. The voltage on the line at the time a signal is sent determines whether the signal is a 0 or a 1. On a 3.3-volt system, an application of 3.3 volts means that it's a 1, while an application of 0 volts means it's a 0.
Other components of the CPU include the Registers and the System Clock. A processor’s clock speed is measured in Megahertz (MHz) and Gigahertz (GHz). Clock speed is the speed at which a processor executes instructions. A Pentium IV typically has a clock speed of 1.4 GHz.
Further research: Buses, System Bus, Expansion Bus

7. Random Access Memory (RAM)
RAM is Primary Storage, also called internal storage.
Serves as computer’s workspace, storing all or part of the program that is being executed, as well as data being used by the program.
RAM stores the operating system programs that manage the operation of the computer.
RAM is Volatile storage:
Power goes, data goes!
More memory = larger workspace
Large programs = large number of instructions
Measured in Bytes (KB, MB, GB, etc.)
Data/instructions are copied into memory as needed.
Not enough memory or corruption of data/instructions in memory can cause crash.
LATEST AVAILABLE RAM ID DDR4 CATEGORY

8. BIOS
EEPROM chips contain permanently written data, called firmware (your BIOS lives here).
EEPROM contains the programs that direct the computer to load the operating system and related files when the computer is powered on.
EEPROM chips are usually recorded when they’re manufactured.
Flash memory is reprogrammable memory. You can upgrade the logic capabilities by simply downloading new software. This saves the expense of replacing circuit boards and chips.

9. PORTS
On computer, a port is generally a specific place for being physically connected to some other device, usually with a socket or plug which we call Connectors
Typical Computer Port found behind a desktop PC

10. CONNECTORS
A connector is any connector used within computers or to connect computers to networks, printers or other devices.
Many types of computer connectors

11. PS/2 Connector
The PS/2 connector are use for connecting keyboard and mouse on the modern PCs. The PS2 mouse connector and port is usually green in colour to distinguish it from the PS2 keyboard, which is purple. It is 6 pin round shape connector

12. USB Port
Universal Serial Bus: a protocol for transferring data to and from digital devices.
Many digital cameras and memory card readers connect to the USB port on a computer.
It is also known as Hotswappable port

13. Firewire IEEE 1394 Port
A type of cabling technology for transferring data to and from digital devices at high speed. FireWire are typically faster than those that connect via USB.

14. RJ45 Ethernet Port
LAN or (Local Area Network) uses a CAT6 cable and a RJ45 connection. The CAT 6 cable  is also called the Ethernet Cable.
Network connection generally uses a 10/100 Mbps/1Gbps speed.

15. DB25 Parallel Port
The printer connects to computer with a Parallel connector. This connector has 25 pins.
Parallel means the device is capable of receiving more than one bit at a time (that is, it receives several bits in parallel).
It is also termed as LPT

16. Ports and Connectors

17. Expansion Cards Accelerated Graphics Port (AGP)
Expansion Cards plug into the expansion slots found on the motherboard. Convenient way to add extra ports or expand the computer’s capabilities.
Accelerated Graphics Port (AGP)
Peripheral Component Interconnect (PCI)

18. Expansion Slots and Cards
Various type of expansion slots are:
Peripheral Component Interconnect (PCI)
Accelerated Graphics Port (AGP)
Industry Standard Architecture (ISA) (obsolete category)
Universal Serial Bus (USB)
Small Computer System Interface (SCSI)
Integrated Drive Electronics (IDE)
Expansion slots are sockets to provide direct connections to the common electrical bus, allowing you to insert a circuit board into the motherboard.
Typical Expansion Cards:
Video Cards
Sound Cards
Modem Cards
Network Interface Cards (NIC)
PCI and PCI-e are the latest architecture used in todat computers

19. Printers Impact Printers Non-Impact Printers
Daisy
wheel
Dot-
Matrix
Inkjet
Laser

20. What is a printer?
An external hardware device responsible for taking computer data and generating a hard copy of that data. Printers are one of the most commonly used peripherals and they print text and still images on the paper.

21. “Impact Printer Working”
These printers have a mechanism that touches the paper to create an image.
These printers work by banging a print head containing a number of metal pins which strike an inked ribbon placed between the print head and the paper.

22. “Non-Impact Printers”
These printers create an image on the print medium without the use of force. They don’t touch the paper while creating an image. Non-impact printers are much quieter than impact printers as they don’t strike the paper.

23. “Dot Matrix Printer”
Working :-The term dot matrix refers to the process of placing dots to form an image.
Limitation:-This is the cheapest and the most noisy printer and has a low print quality.

24. “Advantages/Dis-advatages of Dot-Matrix”
(1) In-expensive.
(2) Low per page cost.
(3) Energy efficient.
Dis-advantages:
(1) Noisy
(2) Low resolution
(3) Limited fonts flexibility
(4) Poor quality graphics output.

25. “Ink-Jet Printer” It uses nozzles instead of pins
It is a non-impact printer producing a high quality print.
It uses nozzles instead of pins
It spray ink from these nozzles

26. How Inkjet Printer works?
(1) Print head having four ink cartridges moves .
(2) Software instructs where to apply dots of ink, which color and what quantity to use.
Color cartridge showing inkjet nozzles.

27. Advantages/ Dis-advantages
(1) High resolution output.
(2) Energy efficient.
(3) Many options to select.
Dis-advantages:
(1) Expensive.
(2) Special paper required for higher resolution output.
(3) Time consuming in case of graphics printing.

28. “Laser Printer” In Laser printer we have cartridge containing toner.
Laser printers used for image formation process.
In Laser printer we have cartridge containing toner.
A drum contained in elctrophotographic cartrige.

29. Network Devices

30. Hubs
Intelligent hubs have console ports, to allow monitoring of the hubs status and port activity.
Passive hubs just repeat any incoming signals to every port available, therefore does not act as a line repeater.
Passive hubs just split signals to multiple ports but do not regenerate the signals, which means that they do not extend a cable’s length. They only allow two or more hosts to connect to the same cable segment.
Active hubs regenerate signals.
Hubs utilise star topology.

31. Hub Pros & Cons Advantages Disadvantages
As an active hubs regenerate signals, it increases the distance that can be spanned by the LAN (up to 100 meters per segment).
Hubs can also be connected locally to a maximum of two other hubs, thereby increasing the number of devices that can be attached to the LAN.
Disadvantages
Bandwidth is shared by all hosts i.e. 10Mbs shared by 25 ports/users.
Can create bottlenecks when used with switches.
Have no layer 3 switching capability. .

32. Switches A switch is a multi-port bridge.
It operates at OSI data link layer 2.
It stores MAC addresses in an internal lookup table.
Temporary switched paths are created between the frame’s source destination.
Some Switches have limited layer 3 IP routing capabilities.
Switches can be configured to use VLANS.
Switches support spanning tree protocol to create resilient networks.

33. Example Topology
Switch
Hub
UTP
10Mbs
Fibre
100Mbs

34. Transceiver Modules UTP Co-axial
Connects to any Auxiliary Unit Interface port (AUI).
Operates at OSI layer 1.
Allows multiple media types to connect to an Ethernet device. i.e. fibre ST/SC,Co-ax cable, and UTP.
UTP
Co-axial

35. Routers Routers are OSI network layer 3 devices
Using interface modules can connect different layer 2 technologies e.g. Ethernet, FDDI, token ring etc…
Routers have the capability to interconnect network segments or entire networks (WANS/MANS).
These devices examine incoming packets to determine the destination address of the data. It then examines its internal routing table to choose the best path for the packet through the network, and switches them to the proper outgoing port.

36. Example Router Topology

37. Data Transmission and Modems

38. Agenda Circuit Mode of transmission Digital transmission
Analog transmission for digital signals - modems
Methods
Classification
Interfaces
Functions
Selection Criteria

39. Circuit Signal rate Speed
No. of signal changes (amplitude, frequency, or phase) on a circuit per second
Baud
Types: dibits, tribits, and quadbits
Speed
No. of bits that a circuit can carry in 1 second
Bits per second (bps) used for measurement

40. Mode of Transmission
Data flow
Physical connection
Timing

41. Data Flow - US Simplex transmission Half-duplex (HDX) transmission
Television and radio
Half-duplex (HDX) transmission
CB radio, terminal
Full-duplex (FDX) transmission
Telephone, computer to computer

42. Physical Connection Parallel transmission Serial transmission Fast
Simple
Line cost
Serial transmission
Complicated transmitter and receive
Decomposing and reconstructing

43. Timing Asynchronous transmission Synchronous transmission
Start/stop bits for character synchronization
Mark (1or stop) /space (0 or start ) bits for bit synchronization
Simple, inexpensive, slow speed transmission
For personal computer
Synchronous transmission
Clock circuitry
One to four synchronization characters for each block of data
Large amount of data on dedicated line

44. Digital Signals Unipolar (positive voltage for 1, no voltage for 0)
Bipolar, nonreturn-to zero (NRZ)
Manchester coding (low-to-high is 1, high-to- low is 0)
Differential Manchester (no transition at the beginning of the bit period is 1, second transition at the beginning of the bit period is 0)
Benefits: self-clocking, and error detection
Bipolar, return-to-zero

45. Benefits of Digital Transmission
Better data integrity (detect & correct error)
Higher capacity cables (fiber-optic)
Easier integration (voice, data, video, etc.)
Better security and privacy (encrypt data)
Lower cost (large-scale integrated circuitry)

46. Digital Transmission of Analog Signals
Quantization
Quantizing noise or digitizing distortion
Codec (coder/decoder): analog-to-digital (A/D) converter & digital-to-analog (D/A) converter
Methods
Pulse code modulation (256 integers, per second)
Adaptive differential pulse code modulation (difference)
Delta modulation (1 for +, 0 for -)

47. Digital Transmission of Digital Signals
Digital transmitter/receiver (data service unit/channel service unit (DSU/CSU))
Simpler & cheaper
Transmitter for shaping & timing the signal, interface between DTE and line
Receiver for protection of excessive voltage, diagnostic and testing

48. Analog Transmission of Digital signals (Modems – I)
Modulation and Demodulation
Receiver (modulation), control unit (auto dial & auto answer), transmitter (demodulation), & power supply
Equalizer in transmitter & adaptive equalizer in receiver (adjust to fit the characteristics of the telephone line)
Methods
Frequency shift keying (FSK)
Phase shift keying (PSK): 180 degree (1 bit), 90 degree (2 bits), 45 degree (3 bits)
Differential phase shift keying (DPSK)
Quadrature amplitude modulation (QAM): combination of 8 phases & 4 relative amplitudes

49. Modem Classification
Simplex, half-duplex, full-duplex transmission modems
Asynchronous or synchronous transmission modems
Acoustically coupled modems (portable)
Limited distance modems/short haul modems (less than 20 miles)
Modem eliminators/null modems (cable less than several thousand feet)

50. Modem Classification - II
Facsimile modems
Error correction and data compression
Modem for fiber-optics circuits
Digital-electrical to digital-optical
Cable modems
DTE to cable television system cable
Data Over Cable Service Interface Specification (DOCSIS) by CableLabs
For large files and not logon process

51. Modem Classification - III
Reverse channel
Slow speed reverse channel for signaling one another
Auto dial/auto answer
Hayes Microcomputer Product, Inc.
Command AT for attention
Internet service provider usage
Dial-backup public telephone network connection for leased telephone line
Internal modem
Single circuit card
No switch to change the parameters and operations

52. Modem Interfaces
Between modem and line
Between DTE and modem

53. Between Modem and Line
Two- to four-wire cable
RJ-11 plug

54. Between Modem and DTE RS-232-C interface V.24 interface
RS-232-D interface
RS-449 interface
RS-336 interface
X.21 interface
X.21bis interface
Current loop interface

55. RS-232-C Interface By EIA and ITU-T V.24 Characteristics Limitations
25-pin connector at both end
digital and serial
Female for DCE and male for DTE
Pins 2 and 3 to pass data, other for signaling
Limitations
feet cable length
2, ,600 bps
Hard to difference 0 and 1 when speed is high and cable is long

56. RS-232-D Interface Specifications for the 25-pin connector
Addition of a shield on the cable
Redefinition of protective ground and some pins

57. RS-449 Interface
37 pins
4,000 feet cable
Not well accepted

58. RS-336 Interface
Automatic dialing from computer to remote terminals for data collection
Not for high speed transmission

59. X. Interfaces X.21 interface X.21bis interface
Digital connection to a digital public telephone network
X.21bis interface
Terminal to packet switch network via analog line

60. Current Loop Interface
Represent 1 and 0 by presence or absence of an electrical current
Simple and inexpensive
Nonstandard
Teletywriter system

61. Other Modem Functions
Reverse channel for signal one another to determine the speed
Auto dial/auto answer
Modem diagnostics
Loop back for accuracy checking

62. Modem Selection Criteria
Digital or analog signals
Asynchronous or synchronous
Speed
Distance
Type of line
Cost
Functions

63. Hard Disk Drive

64. A hard disk drive is a sealed unit that a PC uses for nonvolatile data storage. A hard disk drive contains rigid, disk-shaped platters, usually constructed of aluminum or glass

65. HDD Operation : One side of a platter is called a “head”
HDD Operation : One side of a platter is called a “head”. Hard drives can have different numbers of platters, depending on their design and storage capacity. On the heads, you will see concentric rings (tracks) and pieces of rings (sectors) just like on the floppy disks.

66. Components
The basic components of a typical hard disk drive are as follows:
Disk platters
Read/write heads
Head actuator mechanism-Spindle motor (inside platter hub)
Logic board (controller or Printed Circuit Board)
Cables and connectors
Configuration items (such as jumpers or switches)
The platters, spindle motor, heads, and head actuator mechanisms usually are contained in a sealed chamber called the Head Disk Assembly (HDA).

67. Read Write Heads A hard disk drive usually has one read/write head for each platter surface These heads are connected, or ganged, on a single movement mechanism.

68. Air Filters : Nearly all hard disk drives have two air filters
Air Filters : Nearly all hard disk drives have two air filters. One filter is called the recirculating filter, and the other is called either a barometric or breather filter. These filters are permanently sealed inside the drive and are designed never to be changed for the life of the drive.

69. Spindle Motors
The motor that spins the platters is called the spindle motor because it is connected to the spindle around which the platters revolve. Spindle motors in hard disk drives are always connected directly; no belts or gears are involved.
The spindle motor also must be precisely controlled for speed. The platters in hard disk drives revolve at speeds ranging from 3,600 rpm to 15,000 rpm or more.

70. Logic Boards
All hard disk drives have one or more logic boards mounted on them.
The logic boards contain the electronics that control the drive's spindle and head actuator systems and present data to the controller in some agreed-upon form.
On ATA drives, the boards include the controller itself, whereas SCSI drives include the controller and the SCSI bus adapter circuit.

71. Cables and Connectors
Hard disk drives typically have several connectors for interfacing to the computer, receiving power, and sometimes grounding to the system chassis. Most drives have at least these three types of connectors:
-Interface connector(s)
-Power connector
-Optional ground connector (tab)
The interface connectors are the most
important because they carry the data
and command signals between the
system and the drive.
The power connector is usually the same four-pin type that is used in floppy disk drives, and the same power-supply connector plugs into it.

72. Configurations Items
To configure a hard disk drive for installation in a system, you usually must set several jumpers (and, possibly, terminating resistors) properly.
Master, Slave, and Cable Select are different configurations you can select with jumpers

73. SATA
Serial ATA was designed to replace the older ATA (AT Attachment) standard (also known as EIDE).
It is able to use the same low level commands, but serial ATA host- adapters and devices communicate via a high-speed serial cable over two pairs of conductors.
Serial ATA has distinct key advantages over its predecessor. Cables are very thin with small 7-pin connectors. They can be up to 3 feet (1 meter) in length, and are easily routed to stay out of the way allowing maximum airflow inside the case.
ATA cables limited to 18 inches (46 cm) in length often made connections difficult and also clogged cases blocking airflow, while cooling has become crucial.
SATA also has a far lower power requirement of just 250 mV compared to PATA's 5-volt requirement, and with chip core voltages declining, this speaks well of SATA's future.
First generation SATA has a maximum transfer rate of 150 MBps, and second generation SATA delivers 300 MBps. A third generation SATA set for 2009, "SATA 6Gb/s" will deliver roughly twice the speed of the previous SATA iteration.