Wires from the power supply to the motherboard

and drives

Wires from the power supply to the motherboard

and drives

A Power Supply

Internal view

External view

FanFan

Voltage switchVoltage switch

Socket for power cordSocket for power cord

Power switchPower switch

Power Supply Wire Color Conventions

Color or Component Voltage

Yellow Wire +12

Blue Wire -12

Red Wire +5

White Wire -5

Motor +/- 12

Circuitry +/- 5

System Board Power Supply Connectors

A pair of connectors

A single keyed connector

Notch for keyed connector

Notch for keyed connector

P8P8

P9P9

Drive Power Connectors

Berg connector for floppy disk drive

Berg connector for floppy disk drive

Molex connectors for IDE and SCSI drives

Molex connectors for IDE and SCSI drives

Common Power Problem Symptoms

From the Power Supply Local Machine

Line noise System does not come on

Power sag No fan noise

Power undervoltage or brownout No power light

Frequency variation No beeps

OvervoltageContinuously repeating beep pattern

Power failurePOST errors between 020 and 029

Parity error messages

Unexpected shutdowns or spontaneous reboots

How Surge Protectors Protect Computer Equipment

Extra voltage is diverted to the unit’s ground or neutral wire.

Extra voltage is diverted to the unit’s ground or neutral wire.

Electrical current that is within tolerance limits for the current flows into the unit and powers

its components.

Electrical current that is within tolerance limits for the current flows into the unit and powers

its components.

Electrical current flows from the outlet to the surge protector.

Electrical current flows from the outlet to the surge protector.

BIOS

The Basic Input Output System (BIOS) is the set of instruction commands stored on a ROM chip that is used to start the most basic services of a system.

CMOS

CMOS is an area of memory with battery backup that is used to store the system configuration settings that the ROM BIOS accesses during the startup sequence.

BIOS Settings

BIOS settings are the low-level hardware configuration settings that are stored in the CMOS on every computer.

Accessing the System BIOS

BIOS ManufacturerKey Combination to Access System Settings

Compaq F10 or F12

ALR F2 or Ctrl+Alt+Esc

AMD F1

AMI Delete

PhoenixCtrl+Alt+Esc, Ctrl+Alt+S, or Ctrl+Alt+Insert

The Boot Process

Power supply initializes and sends

signal to CPU.

Power supply initializes and sends

signal to CPU.

CPU checks for BIOS.CPU checks for BIOS.

BIOS

Devices identified in CMOS are detected, configured, and tested. PnP devices are

detected and configured. BIOS checks CMOS to locate the disk

drive to boot.

Devices identified in CMOS are detected, configured, and tested. PnP devices are

detected and configured. BIOS checks CMOS to locate the disk

drive to boot.

Hardware BIOS located, loaded, and run.BIOS information is displayed on screen and runs system tests, including a memory test.

Hardware BIOS located, loaded, and run.BIOS information is displayed on screen and runs system tests, including a memory test.

POST is run by the BIOS.

POST is run by the BIOS.

POST Results

Two short beeps

Audio Output

None

None

None

One short, one long beep

One or more short beeps

Two short beeps

Repeating short beeps

Continuous tone

One long, one short beep

One long, two short beeps

One long, three short beeps

Error code number

Video Output

None

Cursor

DOS prompt

None

DOS prompt

None or incorrect display (garbage)

Probably none

Probably none

Probably none

Probably none

Probably none

Problem

Power

Power

None

Display

None (normal startup beep)

Display

 

Power

Power

Motherboard

Display

Display

See the next table for a list of error codes and their interpretations.

Solution

Check power cords, wall voltage, PC’s power supply.

Check the PC’s power supply; check for sufficient wall voltage.

May be a defective speaker.

Check for monitor power; check video cable; check display adapter.

None.

Check for monitor power; check video cable; check display adapter.

Check the PC’s power supply; check for sufficient wall voltage.

Check the PC’s power supply; check for sufficient wall voltage.

Check to see that all adapters, SIMMs, and chips are seated firmly; check for proper power connections to the motherboard; use diagnostic software or hardware to further troubleshoot the motherboard.

Check for monitor power; check video cable; check display adapter.

Check for monitor power; check video cable; check display adapter.

POST Error CodesPOST Error Code

02#

01##

0104

0106

0151

0162

0163

164 or 0164

199 or 0199

02##

201 or 0201

0202

03##

0301

0302

06##

0601

0602

17##

1701

1704

1707

1714

1730 - 1732

Problem

Power

Motherboard

Interrupt controller

Motherboard

Real-time clock or CMOS RAM

CMOS checksum error

Time and date (clock not updating)

System memory configuration is incorrect

User-indicated device list is incorrect

Memory

Memory error (may give memory address)

Memory address error

Keyboard

Stuck key (scan code of the key may be indicated)

Keyboard locked

Floppy disk drive or controller

Floppy disk adapter failure

Disk failure

Hard disk or adapter

Drive not ready or fails tests

Hard drive controller failure

Track 0 failure

Drive not ready

Drive adapter failure

Error Message Possible Reason

Bad or missing command interpreterNon-system disk or disk error

System can’t access the operation system.

Display Type MismatchVideo settings don’t match the monitor attached to the system.

Memory Size MismatchThe amount of RAM detected and the amount specified in CMOS don’t match.

CMOS Checksum Failure The CMOS memory is corrupted.

CMOS Error Codes

CPU

The Central Processing Unit (CPU) is the integrated circuit that controls all of the system components.

Bus Types

Internal External System (frontside) Data Address Control Backside

CPU Performance Factors Clock speed Millions of Instructions Per Second (MIPS) Amount of RAM that a processor can access Multiprocessing Cache Superscalar Superpiplining Speculative execution Branch prediction Register renaming Out-of-order completion Dual Independent Bus (DIB) Multimedia Extensions (MMX) Single Instruction Multiple Data (SIMD)

Characteristics of Popular Processors

Name Internal Bus Width (bits)

System Data Bus Width (bits)

System Address Bus Width (bits) Clock Speed

SpeedAddressable RAM

8086 16 16 20 4.77-10 1 MB

8088 16 8 20 4.77-8 1 MB

80286 16 16 24 6-12 16 MB

80386DX 32 32 32 16-40 4 GB

80386SX 32 16 24 16-33 16 MB

80486DX 32 32 32 25-50 4 GB

80486SX 32 32 32 16-33 4 GB

80486DX2 32 32 32 50-80 4 GB

80486DX4 32 32 32 75-120 4 GB

AMD 5x86 32 32 32 133 4 GB

Cyrix 5x86 32 32 32 100-200 4 GB

Pentium 32 64 32 60-200 4 GB

Pentium MMX

32 64 32 166-233 4 GB

Cyrix 6x86 32 64 32 100-150 4 GB

Characteristics of Popular Processors (Cont.)

Name Internal Bus Width (bits)

System Data Bus Width (bits)

System Address Bus Width (bits) Clock Speed

SpeedAddressable RAM

AMD K5 32 64 32 75-116 4 GB

Pentium Pro 32 64 36 150-200 64 GB

Pentium II 32 64 36 233-333 64 GB

AMD K6 32 64 32 166-266 4 GB

Cyrix 6x86 MX

32 64 32 150-187 4 GB

Celeron 32 64 32, 36 266-1300 4 or 65 GB

Pentium II Xeon

32 64 36 400-450 64 GB

Pentium III 32 64 36 450-1400 64 GB

Pentium III Xeon

32 64 36 600-1000 64 GB

Pentium 4 32 64 32 1.3-2.4 GHz 4 GB

Itanium 64 64 44 733-800 16 TB

AMD Athlon 32 64 43 500-2133 8 TB

Intel CPUs

CPU Core Speed Bus Speed

Pentium 75 – 200 MHz 50 – 66 MHz

Pentium Pro 150 – 200 MHz 60 – 66 MHz

Pentium with MMX 150 – 266 MHz 66 MHz

Pentium II 233 – 400 MHz 66 – 100 MHz

Pentium II Xeon 400 – 450 MHz 100 MHz

Celeron 266 MHz – 2 GHz 66 – 400 MHz

Pentium III 533 MHz – 2 GHz 66 – 400 MHz

Pentium III Xeon 500 MHz – 1.4 GHz 100 – 133 MHz

Pentium 4 1.38 – 8 Ghz 400 – 533 MHz

Xeon 1.42 – 8 GHz 400 MHz

Examples of CPU Sockets

Slot 1 (For SECC Packaging)

A ZIF Socket

A Heat Sink with Fan

FanFan Heat sinkHeat sink

Instruction Set Description

Complex Instruction Set Computer (CISC)

A design strategy for computer architecture that depends on hardware to perform complicated instructions.

Reduced Instruction Set Computer (RISC)

A design strategy for computer architecture that depends on a combination of hardware and software to perform complicated instructions.

Explicitly Parallel Instruction Computing (EPI)

A design strategy for computer architecture that is meant to simplify and streamline CPU operation by taking advantage of advancements in compiler technology and by combining CISC and RISC design strategies.

Instruction Sets

A System Board Without a Daughter Board

Expansion slotsExpansion slots

RAMRAM

CPUCPU

AGP slotAGP slot PortsPorts

Drive interfacesDrive interfaces

Clock Speed

Clock speed refers to the number of cycles per second or frequency at which the CPU operates (e.g. 800 MHz).

Full-Size AT System Board

AT socket 7 motherboard

ChipsetChipset

ZIF socketZIF socket

Keyboard connectorKeyboard connector

AGP slotAGP slot

PCI slotPCI slot

ISA slotISA slot

Power connector (ATX)Power connector (ATX)

BIOS chipBIOS chip

SDRAM slotsSDRAM slots

Baby AT System Board

REAR

FRONT

Keyboard connector

Power connector

Peripheral connectors

Memory slots

PCI/ISA slots

CPU

LPX System Board

REAR

FRONT

PCI/ISA slots on riser

Memory slots

Peripheral connectors

CPU

ATX System Board

REAR

FRONT

I/O connector

Power connector

Peripheral connectors

Memory slots

PCI/ISA slots

CPU

NLX System Board

Peripheralconnectors

Power connector

Memory slots

PCI/ISA slots

AGP port

FRONT

REAR

CPU

System Case Enclosure Styles

Full-size towerFull-size tower Mid-size tower

Mid-size tower

Micro-size tower

Micro-size tower DesktopDesktop

A Generic ATX System Board

Lithium backup battery

Lithium backup battery

UltraDMA EIDE connectorUltraDMA EIDE connector Floppy disk drive connectorFloppy disk drive connector

PS/2 mouse and keyboard connectors

PS/2 mouse and keyboard connectors

CPUCPU

AGP portAGP port

ATX power supply connector

ATX power supply connector

PCI expansion slotsPCI expansion slots

DIMM socketsDIMM sockets

9-pin serial port connector9-pin serial port connector25-pin parallel port connector25-pin parallel port connector

USB connectorUSB connector

DIP Switches and Jumpers

Closed, or On

Open, or Off

Jumper blockJumper block

Switch or switch blockSwitch or switch block

Open, or OffClosed, or On

Common Sources of System Board Problems

Computer viruses infecting the system, including the BIOS. Loose connections between system components and the system

board. Out-of-date BIOS. CMOS battery is not holding the BIOS information. Damage to the CPU due to overheating or electrical damage. Electrical shorts on the system board due to improperly seated

components, power surges, or ESD. Physical damage to the system board.

Memory

Memory Type Volatile/Stable Use

CMOS Stable – it is maintained by a battery even when the system is off.

Holding the system configuration information.

ROM (Read Only Memory)

Stable – information is permanently stored on the chip.

Holding system or card startup information.

RAM (Random Access Memory)

Volatile – temporary while the system is in use.

Holding program instructions and data so they can be processed by the CPU.

SAM (Sequential Access Memory)

Volatile – often used for a memory buffer.

Holding data in a sequential order.

A ROM Chip

A PROM Chip

An EPROM Chip

An EEPROM Chip

RAM

RAM Type Description

FPMFast Page Mode memory is faster than previous RAM types because it reads an entire row rather than reading a row and column address at a time.

EDOExtended Data Output memory is faster than FPM memory because it doesn’t require the wait states necessary for FPM.

SRAM Static RAM is used for cache memory.

DRAM Dynamic RAM is used on single and dual in-line memory modules (SIMMs and DIMMs).

RDRAMRambus DRAM is implemented on a RIMM memory module.

SDRAM and DDR SDRAMSynchronous DRAM runs at high clock speeds and is synchronized with the CPU bus.Double Data Rate SDRAM is a replacement for SDRAM.

VRAM Video RAM is a special type of DRAM used on video cards.

WRAM Windows RAM is a special type of video memory.

A SIMM

A DIMM

A RIMM

Parity

8 data bits8 data bits 1 parity bit1 parity bit

Adding RAM to a System

20 pins20 pins 88 pins88 pins60 pins60 pins

LockLock

Symptoms of Memory Problems Computer crashes or reboots itself periodically. Application data is corrupted. Memory errors are displayed on the screen. Computer appears to boot, but the screen remains blank. Computer does not boot; POST beep codes are heard. Newly installed memory is not recognized.