Computer Maintanance

Dr. Mostafa Elgamala
Computer Maintenance
Essentials

1Dr.Eng. Mostafa Elgamala – Optimal Vision – 01004413398
Motherboards (Main board or system board), processors, and memory
 3 form factor "design" ATX, Micro ATX, ITX. ATX "advanced technology extended" is
upgrade of AT MB by intel 1990 "30,5 * 24,4 cm", M ATX "24,4*24,4", ITX by via
"17,7*17,7" to "6*6 mobile ITX".
Motherboard components
 Bus architecture
 Chipset : perform peripheral functions interface for memory and expansion slots, for the
processor. The functions of chipset divided into two major function groups
o North bride function: management of high speed peripheral communication
"responsible for communication with AGP, PCIE, memory", much of the pc
performance relies on its specification. Communication between processor and
north bride occur over front side bus "FSB"
o South bridge : provide support to the onboard slower peripherals like ps/2, serial
port, parallel port, SATA,PATA, USB, network, PCI. Do not represent a performance
bottleneck.
Chipset
 Expansion slots
o PCI : "peripheral components interconnect" operate at 33 or 66 MHz over 32 bit
channel , so data rate 133 or 266 MBps
o PCI-X : for servers – up to 533 MHz over 64 bit bus , so max throughput 4.3 GBps.
o AGP: "Accelerated graphics ports" designed to be a direct connection between the
video circuits and memory. Up to 2.133 GBps.
o PCIe: "express" upgrade of AGP and PCI, up to 8 GBps.
o CNR" for analog circuits "modems , audio" to increase motherboard performance.
 memory slots & cache
o SIMM : "single inline memory module ", old form factor
o DIMM: "dual inline memory module" (168 bin , 184 bin , 240 bin)

o Micro DIMM : for labtop
o SODIMM: for labtop
Virtual memory "swap file, paging file" concept
Cache : layer 1 or level 1 (internal cache) into the processor
Layer 2 or level 2 (external cache) in the MB
` layer 3 (optional) if layer 2 cache in the processor package so the cache on
the MB called layer 3 cache
DDR RAM
SODIMM

Micro DIMM
 CPU sockets : Pin grid array (PGA-called socket A) or Land grid array (LGA- called socket T),
most common types Intel (Celeron, core i3, core i5, core i7), AMD (Athlon).
PGA
LGA
 Power connectors
 BIOS chip (ROM BIOS) : contains BIOS system software that boots the system and allows
the operating system to interact with Hardware- manufactured by "AMI, Phoenix/Award,
winbond, ….). BIOS make POST "power on self test" then select boot device then execute
MBR "Master boot record" ,finally call O.S boot loader. We can call the software in BIOS
chip Firmware which is software encoded in hardware. CMOS memory is integrated into

the BIOS or south bridge and it keep time , date, boot sequence , passwords, CPU and
Harddisk settings.
BIOS
 Jumpers and DIP "Dual in-line package" switches
DIP switch

 Front-panel connectors : power light and switch, reset switch, drive activity lights, audio
jacks, USB ports.
Front panel connectors

Mother boards
Processors characteristics
 Hyperthreading technology "HTT": HTT capable processors appear to O.S to be two
processors at a time (O.S must support SMP) "Intel feature".
 Multicore "Dual core or Quad core": separated processors on the same package "2 dies".
Note that SMP is not a benefit if the applications are not written for parallel processing.
 Throttling: reduce operating frequency of CPU during less demand or battery operation
"for heat and system battery drain".
 Speed: measured by MHz or GHz
 32 bit & 64 bit processors: the set of data lines between CPU & primary memory can be 32
or 64 bits wide (more data can be processed per unit time)
 Virtualization support
Memory
 Motherboard, processor, O.S have memory limits
 Single and double-sided memory
 Memory types
o DRAM

 Asynchronous DRAM (FPM RAM, EDO RAM, BEDO RAM) – old , slow
 synchronous DRAM (SDR SDRAM, DRDRAM "old, slow double rate", DDR
SDRAM "double data rate", DDR2 SDRAM "quad data rate", DDR3 SDRAM
"100 MHz *8")
o SRAM (used for cache memory – faster – complex – expensive – very low access
time "10 ns")
o ROM (PROM "writeable for first time", EPROM "use U.V to write or electrically"-
EEPROM "flashes")
Cooling: passive (heat sink), active (fans, liquid, liquid nitrogen, helium)
Hard Disk Drive system contains:
1- Controller : control how the drive operate , how the data is encoded onto the platter
2- Hard disk: physical storage medium
3- Host bus adapter (HPA): translator – converting signals from the controller to
understandable signal by computer- integrated in the motherboard circuits in the south
bridge.
Hard disk components:
 Platter
 R/W heads
 Tracks: drawn magnetically around the surface of the platter
 Sectors: smallest unit of storage on the disk's platters.
 Cylinder: no. of cylinder = no. of tracks can be found on any single surface of any single
platter.
 Cluster: O.S group no. of sectors- configurable (max= 64 k (128 sector))
 no. of cylinders * no. of heads =total no. of tracks
 total no. of tracks*no. of sector/ track= total no. of sector
 total no. of sectors * 1/2 KB = total size of H.D
 Hard disk speed from 5400 RPM to 15000 RPM

Solid-state drives: depend on solid-state memory technology found in flash memory but limited to
finite no. of writes (including erase). More quickly, low power, less heat, less susceptible to
damage from physical shock. It has two types volatile DRAM, non-volatile flash based.
SSD
Optical devices:
 CDROM: 650 MB – red laser
 DVD-ROM :
o 4.7 GB – single-sided disc – red laser
o 9.4 GB double-sided disc – red laser
o 17.1 DVD- double layer – red laser
 BD-ROM (Blue- ray)
o 25 GB – one layer- single side
o 50 GB – double layer
CD drive operation
Optical drive data rate:

 CD from 1x to 52x (x=150 KBps)
 DVD from 1x to 16x (x=1.4 MBps)
 BR from 1x to 16x (x=4.5 MBps)
Note: increase the laser power will melt the crystalline media surface. So there are types
which can be written like DVD-RW.
Note: Some types can be erased & rewritten.
Disk interfaces
 IDE (PATA): "Integrated device electronics" – 40 bin – ATA 7 (up to 150
MBps), ATA 8 "up to 300 MBps".
 SATA: SATA I (1.5 GBps), SATA II (3GBps), SATA III (6GBps)
 SCSI: 7 device per interface
RAID: Redundant array of independent disks
o RAID 0 (disk striping)
o RAID 1 (disk mirroring)
o RAID 5
o RAID 6
RAID
Tape: up to 1.5 TB- slow
Flash memory
 SD/micro SD
 MMC
 Flash storage
USB external disk
Firewire disk
eSATA disk: (need external power suplly)

Swapping : cold-swappable devices like PS/2 devices, hot/warm swappable devices like USB and
flashes.
Power supply: convert 110 or 220 V AC to 3.3 VDC, +/- 5VDC, +/- 12 VDC
Power connectors
 Standard peripheral power connector "Molex"
Molex connector
 Floppy "Berg" (5 V –red, 12 V – yellow, ground – black)
 ATX power connector for motherboard
 ATX 12 v fro PCI-Express
 SATA power connector
Common expansion cards
1- Video: PCI > AGP > PCIe

VGA
2- Multimedia:
 sound card "mic – speaker- game port DA15"
 TV- tuner
Sound card
TV-tuner
3- I/O
 Serial "RS-232"
 Parallel
4- Communication
 NIC
 Wireless NIC
 Cellular card
 Modem

NIC
Modem
Characteristics of connectors & cable
1- D-connectors: (examples: DE9 (serial male - female)( Standard serial RS-232- max rate 57
kbps) , DE 15 (video port male cable – female port), DB 25 (parallel port – cable))
2- RJ- connectors: RJ-11 , RJ-45
RJ-11

RJ-45
3- Other types of ports:
 USB (serial)(< 5 VDC): up to 127 device in single port:
* USB1 > 12 Mbps
* USB2 > 480 Mbps (100 ma > 500 ma)
* USB3 > 5 Gbps (150 ma >900 ma)
USB connectors: type A, standard mini B, type B, alternate mini B- micro B
connector.

 IEEE 1394 (fire wire- serial): 400 Mbps > 3.2 Gbps – (30 VDC-1.5 amp)
 Infrared: max 4 Mbps , line of sight
 Audio/ video jacks: RCA, HDMI, DVI, S-video.
DVI
HDMI
 PS/2: called mini-DIN 6 connector
 Coaxial: CATV F connector

CATV connector
 Game port
Input devices
1- Mouse: (trackballs, touchpad, point stick, wireless mouse, wheel mouse, laser mouse)
2- Key board
3- Scanner
4- Barcode reader – Quick Response (QR) reader
QR- code
5- Digitizer devices: convert analog source like artwork to binary bit stream
6- Biometric devices: fingerprint scanners, retinal scanners, voice recognitions device, face
recognition device.
7- Touch screen
8- KVM switch

KVM
9- Joy sticks
10- Web cam
11- Digital cam
12- Audio input
Output devices:
1- Printers
2- Speakers
3- Display devices
Video display unit
1- CRT: electron gun shoots a beam of electrons toward a special chemical dots called
phosphor.
Resolution: define s how many pixels used to draw the screen. More info can be display in
the same area.
Color depth: no. of colors in which each pixel can be displayed "24 bit color depth mean
2^24 = 16,777,216 color per pixel, true color mean 17 million color" so each pixel need 24
bit of memory to sore one screen element. 1024 col *768 row = 786,432 pixel require 2.24
MB.
2- Liquid crystal display (LCD): backlight "fluorescent lamp placed behind" generate light
which diffused by crystalline liquid in each pixel location. Need large amount of power.
3- Light emitting diode (LED): LED instead of fluorescent bulbs. Operate on DC. The updated
display called OLED.
4- Plasma display: ionized particles inside the screen.

To upgrade your PC you can increase CPU speed or RAM size or Video card capabilities or disk
storage or Network B.W depending on your needs.
LABTOPs
 3 main components: display (LCD or LED), the case frame (metal structure inside the
labtop), the case (plastic case).
 Video circuit placed on a thin board that connects directly to M.B, this is called riser card or
daughter board.
LABTOP M.B
 Processor attached to M.B so no upgrade available. It use SODIMM or MicroDIMM. The
mice can be track ball, touch pad, point stick, touch screen.
 Laptops use PCMCIA "PC card", Express card "support USB2, PCIe", or mini PCI as
expansion buses.
 Docking port & docking station act as extension to M.B, the station contain USB, firewire,
monitor, printer, keyboard, etc.
 AC power source needs to be rectified to DC, An inverter is used to convert the DC power
to AC for the back light in the LCD.
 Batteries can be: Nickel Cadmium "NiCd", Lithium ion "Li-ion", Nickel metal hydride "NiMh"
, or Lithium-polymer "Li-poly".
 Laptops need power adapters: AC adapter for normal operation or DC adapter for cars and
airplane.
 Laptops need also Wi-Fi antenna for wireless network, and cable lock for physical security.

Operating system basics
Basic functions:
 Interfacing with hardware
 Provide a platform on which other application can run “gives users an interface with the
computer to send commands and receive feedback (output) “, to do this it must
communicate with H/W.
In details it is responsible for memory & processor management, I/P & O/P, access devices, disk
management.
Application: used to make a particular task
Drivers: S/W written for the purpose of tell O.S how to access H/W “each H/W has unique features
& configuration”
Operating system terms:
1- Version
2- source : actual code (open source, closed source “proprietary”
3- GUI/CLI
4- Multitasking: O.S divide the processor time between applications.
5- Multithreading: app. Ability to have multiple requests in to the processor at one time
“faster app. performance”
6- 32 bit & 64 bit O.S (= x86 & x64)
7- HCL & min. requirements (XP 64M,128 MB – 233 MHz)(win 7 – 1GB , 2 GB(64 bit) – 1 GHz)
File management
File names cannot contain (? ,,/)
File extension used to identify the file’s type
doc, docx, txt > documents
mp3 , wav > sound
jpeg , bmp, gif > pictures
html , htm > internet files
exe ,msi > executable files
mpg , asf > video
File names are not case sensitive
File attributes can be read only, hidden, compressed, and encrypted
Compression state depend on file type (word and bmp > 80 % compressible, exe, gif, jpeg > 2%
compressible)

Operating system administration
1- Control panel applets
Date & time
Regional & language options
Programs
System & security applet
Power options
2- Command prompt
O.S command-line tools
Taskkill
Shutdown
Tasklist
Diskpart
Format
Sfc
Chkdsk
3- Windows registry (regedit or regedt32)
It is configuration database, registry is broken down into hives. Number of files are
created corresponding to each of the different hives “most have not extension“ like
ntuser.dat, system, software, security, sam, default.
 Hkey_classes_root > file name extension mapping
 Hkey_current user > configuration information about user “desktop setting
history”
 Hkey_local_machine > configuration information about computer H/W & S&W
 Hkey_user > information about all logged users “Hkey_current_user is asubkey of
this hive”
 Hkey_current_config > quick access for some keys in Hkey_local_machine
Registry files exist in c:windowssystem32config. If it is corrupted you can press f8 at
startup and select “last good known configuration”, or restore from backup.
Administration tools
1- Task manager “ctrl+shift+esc , or ctrl+alt+del”
2- Computer management
3- Services
4- Windows system configuration tools “msconfig, msinfo32”
Disk management
Partitioning: logical division
Formatting: create file allocation table which used to keep track of where files are . ex FAT,
FAT32, NTFS, CDFS. “quick format does not check for bad sector”

Disks divided to basic storage (primary & extended) and dynamic storage (simple, spanned
striped which can be extended online)
Boot partition must be active
We can make defragmentation to make the data occupy contiguous space to.
Win XP
Operating system installation options: select boot media, installation types, network
configuration, file system types, dual boot support.
Key boot files
NTLDR (start O.S loading) > boot.ini (determine the location of O.S files) > Ntdetect.com >
NToskrnl.exe > system files (system/system32, hal.exe, etc)
Boot process:
 MBR loaded into memory and it find boot sector on active partition.
 NTLDR is loaded to memory and it process boot.ini.
 NTLDR run Ntdetect which check for H/W and give its information to NTLDR which
passes these information to Ntoskrnl after loading.
 NTLDR load Ntoskrnl & hal.dll (enable communication between H/W & O.S)
 NTLDR load registry hive Hkey_local_machine to load drivers needed at boot.
 NToskrnl initialize loaded drivers.
Winlogon.exe loads to appear logon screen.
Win 7
3 main edition home (16 GB, 1 processor), professional, ultimate (192 GB, 2 processor)
No upgrade from XP
Key boot files
Bootmgr > BCD > winload.exe > winresume.exe > ntoskrnl.exe > system files
(system/system32, hal.dll, smss.exe, winlogon.exe, sass.exe)
Troubleshooting
 Identify the problem by talking to customer to gather information (to determine if the
problem S/W, H/W, or user problem).
 Eliminate possibilities and use external resources.
O.S troubleshooting: Win 7 consist of 50 million line which wrote by about 2000 developer.

 Blue screen of death (BSOD): try safe mode, last good known configuration, if there are
missing dll find a copy online or backup.
 Compatibility error may be exist in the old device drivers
 Slow system: check performance from control panel > troubleshooting > check for
performance.
o May be: virus, defragmentation, application problem.
 If there are missing NTLDR file > boot from CD then choose recovery console then write
“fixboot” (“bootrec /fixboot” in win 7)
 If there are missing boot.ini file > boot from CD then choose recovery console then write
”bootcfg” (“bootrec /rebuildbcd” in win 7)
 SFC: overwrite corrupted system files from “in win 7 c:windowswinsxsbackup - in win
xp c:windowssystem32dllcache”
 Msconfig:
 Defrag:
 Common boot options “f8”:
 Safe mode (VGA, standard mouse and keyboard)
 Enable boot logging (write boot messages to NTBTlog.txt)
 Enable vga mode (low resolution video)
 Last good known configuration
Create restore point
To backup system configuration files.(XP- start> all program>accessories>system
tools>system restore), (Win 7 – start> control panel> system& security> system protection> create
restore point)
H/W troubleshooting tips
 Remove dust & paints “make overheat & conduct electricity on their surface”
 Cooling checking
 H.D problems : if there are loud clicking , the disk is bad, if it is slow try to defrag or
remove files, check the cable
 Video problems: boot in vga mode, try another cable or monitor, toggle LCD in labtops.
 Memory problems: may generate BSOD, may be due to application problems.
 The diagnostic program build in to bios called POST which check on processor, RAM,
video card, and basic H/W functionality. If there are single beep code so it is OK. The
number and duration of beeps tell what is the problem and it is differ between BIOS
manufacturers

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