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2.1 Identify basic terms, concepts, and functions of system modules

• System board
• Power supply
• Processor/CPU
• Memory
• Storage devices
• Monitor
• Modem
• Firmware
• Boot process
• BIOS
• CMOS

 

 

System board

• It contains the microprocessor, ROM, RAM, cache memory sections, expansion slot connectors, microprocessor support ICs.
• receives power from the power supply through a pair of 6-pin connectors labelled P1 and P2, often located at the rear-right corner of the system board

 

Power supply

• Provides electrical power for every component of the system and AC power to the monitor
• Delivers power to the system board through P8 and P9 pins
• Yellow : +12 V Disk drive motors
• Blue : -12 V
• Red : +5 V System board and adapter cards
• White : -5 V

Processor/CPU

80386SX

• 32 bit word size & 16 bit data path
• surface-mount, 100 pin, plastic, quad flatpack package

80386DX

• 32 bit word size & 32 bit data path
• surface-mount, 100 pin, plastic, quad flatpack package

80486SX

• 32 bit word size & 32 bit data path
• no built in math coprocessor

80486DX

• 32 bit word size & 32 bit data path
• built in math coprocessor
• 486DX2 - external clock speed is half of the internal clock speed
• 486DX4 - external clock speed is 1/3 of the internal clock speed

Pentium

• 32 bit word size & 64 bit data path
• Superscalar - allows multiple instructions to be executed simultaneously
• uses socket 7

Pentium MMX

• 57 instructions for manipulating video, audio and graphic data
• SIMD - Single Instruction Multiple Data
• more built in cache on chip

Pentium Pro

• on-board L2 Cache
• Multiple Branch Prediction
• Data Flow Analysis
• Speculative Execution
• single and dual processors

Pentium II

• Single Edge Cartridge (SEC) design
• core and L2 Cache in cartridge
• single and dual processors

 

Memory

ROM (Read Only Memory)

• non-volatile memory
• contains POST and SETUP

CMOS

• contains BIOS
• uses a battery to maintain its data when the system is powered off

RAM (Random Access Memory)

• volatile, does not maintain data without power
• contains operating system and any active application
• Shadow RAM - allows the system to operate faster by loading BIOS in RAM

Conventional memory

• the first 640 k of memory

Upper memory

• the memory between 640 k and 1024 k
• DOS drivers are loaded here

Extended memory

• the memory above 1024 k

Expanded memory

• switching banks of memory outside the DOS memory area
• it is addressed in pages of 16 k

HMA (High Memory Area)

• the first 64 k of extended memory

 

Storage devices

Floppy Disk Drives (FDD)

• 3.5" or 5.25" size
• Double Side-Double Density (DS-DD)
• Double Side-High Density (DS-HD)
• FDD controllers usually use DMA channel 2

Hard Disk Drives (HDD)

• much higher storage capacity and data transfer rates
• much lower cost
• cluster-->sector-->track (512 k)
• seek time is the time that it takes the head to find the requested track
• latency period is the time it takes the sector to move under the head
• access time is the time it takes a hard drive to find data
• data transfer rate is how fast the drive sends data to the system
• Head to Disk Interference (HDI) = Head crash

 

Monitor

• dot pitch is the space between pixels measured in milimeters
• refresh rate is the number of times the display is redrawn every second
• persistence is the amount of time it takes the illuminated trace to dissipate from the fluorescent coating of the CRT
• non-interlaced - display full image in single pass of electron gun

Graphic Resolution

CGA	640 x 200
EGA	640 x 350
HGA	740 x 348
VGA	640 x 480
SVGA	1024 x 768

 

Modem

• converts digital signals into analog signals and vice-versa
• consists of two blocks : Modulator and Demodulator
• Simplex Mode - sends signals in only one direction
• Half-Duplex Mode - exchanges data with another modem, but only in one direction at a time
• Full-Duplex Mode - both modems send and receive data simultaneously
• Common bit rates : 2400, 9600, 14400, 28800, 33600, 56000 bps
• Synchronous Transmission - places synchronization signals at the beginning of each data block, to synchronize the transmitter and the receiver. Associated with high speed modems
• Asynchronous Transmission - places a synchronizing bit at the beginning and at the end of each eight bit character. Associated with low speed modems

 

Firmware

• proprietary software developed by different companies

 

Boot process

• After initialization and POST tests, the BIOS checks the disk drive units for a bootable file (file that controls the operation of the system)
• Bootstrap loader - a program that looks for the command procesor file (COMMAND.COM). After it finds it, it moves it in system RAM along with MSDOS.SYS and IO.SYS. All these files must be in the root directory in order to boot MS-DOS. These are the minimum files that MS-DOS needs to boot
• Typical loading order of MS-DOS : IO.SYS, MSDOS.SYS, CONFIG.SYS, COMMAND.COM, AUTOEXEC.BAT
• Cold boot - system started from OFF condition
• Warm boot - system restarted from ON condition

 

BIOS (Basic Input/Output SYSTem)

• permanently stored in ROM memory
• performs POST (Power-On Self Test)
• performs initialization - places starting values in the system's various programmable devices
• checks the disk drives for the Boot Becord in order to load the Operating System in RAM memory

 

CMOS (Complemetary Metal Oxide Semiconductor)

• CMOS Setup is accessed by pressing the DEL key
• When setting up a computer for the first time, or when adding new components to the system, you need to run CMOS Configuration Setup
• The values are stored in CMOS registers which are read each time the system is booted up