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Active motherboards – sockets and slots – Intel D850GB – Pentium4 mother board – expansion slots – form factor – upgrading a mother board – chipsets – north bridge – south bridge – CMOS – CMOS optimization tactics – configuring the standard CMOS setup – motherboard BIOS – POST – BIOS features – BIOS and Boot sequences – BIOS shortcomings and compatibility issues – power supplies and power management – concepts of switching regulation – potential power problems – power management.

Mother Board

Most modern motherboards have at least the following major components:

n Processes socket/slot

n Chipset

n Super i/o controller

n ROM bios

n RAM sockets

n Bus slots

n CPU voltage regulator

n Battery

mb, mainboard, mobo, mobd, backplane board, planar board, or system board. The Motherboard is a printed circuit that is the foundation of a computer and allows the CPU, RAM, and all other computer hardware components to function with each other. Below is a graphic illustration of the ASUS P5AD2-E motherboard and some basic explanations of each of the major portions of the motherboard

Sockets and slots

The motherboard has one or more sockets or slots into which the processor is inserted. The type of processor that can be used is defined by the type of socket or slot present on the motherboard. Intel has historically defined the processor socket standards, but competing chip makers have been able to use the same standards quite successfully

l Motherboard and processor must match

l Slots 1 and 2 are proprietary Intel slots

l Slot A and Socket A are proprietary AMD connectors

Socket 1
This is an old slot. Its found on 486
motherboards and supports 486 chips, plus the DX2, DX4 Overdrive. It contains 169 pins and operates at 5 volts. The only overdrive it will support is the DX4 Overdrive.

Socket 2
This Intel socket is a minor upgrade from the Socket 1. It has 238 pins and is still 5 volt. Although it is still a 486 socket and supports all the chips Socket 1 does, it has the minor addition of being able to support a Pentium OverDrive.

Socket 3
Another Intel socket, containing 237 pins. It operates at 5 volts, but has the added capability of operating at 3.3 volts, switchable with a jumper setting on the motherboard. It supports all of the Socket 2 processors with the addition of the 5×86. It is considered the latest of the 486 sockets.

Socket 4
We move into Pentium class machines with the Socket 4, by
Intel. This socket has 273 pins. It operates at a whopping 5 volts. Due to this voltage and the lack of any multipliers, this socket basically had no where to go but the history books. It only supports the low-end Pentium 60-66 and the Overdrive because these chips are the only Pentiums operating at 5 volts. Beginning with the Pentium-75, Intel moved to the 3.3 volt chip.

Socket 5
This socket operates at 3.3 volts with 320 pins. It supports Pentium class chips from 75MHz to 133MHz. Newer chips will not fit because they need an extra pin. Socket 5 has been replaced by the more advanced Socket 7. There are socket converters out there that can allow you to run more modern socket 7 processors in these socket 5 sockets. While socket 7 processors are still old by today’s standards, these converters can allow you to get more life out of your socket 5 motherboard.

Socket 6
You might think this is a nice Pentium socket class, but it is meant for 486’s. It is only a slightly more advanced Socket 3 with 235 pins and 3.3 volt operation. This socket is forgotten. The market never moved to use it because it came out when 486’s were already going of out style and manufacturers couldn’t see pumping money into changing their designs for a 486.

Socket 7
Socket 7 was the most popular and widely used socket for quite awhile. It contains 321 pins and operates in the 2.5-3.3 volt range using a split voltage (different I/O voltage and core voltage). It supports all Pentium class chips, from 75MHz on up, MMX processors, the AMD K5, K6, K6-2, K6-3, 6×86, M2 and M3, and Pentium MMX Overdrives. This socket was the industry standard and was being used for sixth-generation chips by IDT,
AMD and Cyrix. Intel, however, decided to abandon the socket for it’s sixth-generation lineup. Socket 7 boards incorporate the voltage regulator which makes voltages lower than the native 3.3 volt possible.

Socket 8
This is a high-end socket used for the Pentium Pro. It has 387 pins and operates at 3.1/3.3 volts. It is designed especially to handle the dual-cavity structure of the chip, so the socket is a bit longer than the others. It is more rectangular than other sockets, which are more square. Since Intel decided to move on to Slot 1, the Socket 8 is a sort of dead end unless you really want to use a Pentium Pro.

Slot 1
Intel completely changed the processor paradigm with this new format. Instead of the processor core being in a socketed package, Intel placed their 6th generation Pentium II onto a daughtercard. Whereas socket 7 boards typically had the L2 cache on the board itself, this daughtercard has the L2 cache on the card itself. This increases speed by allowing the processor to communicate quickly with the L2 cache without having to be limited to the speed of the
system bus, as was the case with socket 7. Slot 1 itself has 242 pins and operates at 2.8-3.3 volts. The Slot 1 is used mainly for the P2,P3 and Celeron, but Pentium Pro users can use the slot by mounting their processors in a socket 8 on a daughtercard which is then inserted into the Slot 1. This converter gives Pentium Pro users the ability to upgrade later.

The release of this slot was mostly a competitive blow to AMD more than anything else. The socket designs previously used were not patented to be sure competitors could not use it. With the release of Slot 1, the wiring structure was patented so that no other manufacturer could use the design without approval from Intel. This is why we do not see any AMD processors making use of Slot 1. They had to create their own slot, slot A, to move onto the slotted interface.

Slot 1

Developed by Intel to replace their Zero Insertion Force (ZIF) sockets. Using Slot 1, the CPU is packaged in a 242-contact Single-Edge Contact Cartridge. The cartridge may contain up to two CPUs and an L2 cache. Intel’s Pentium II, Pentium III, and some Celeron processors use the Slot 1 configuration.

Slot 2

Essentially a 330-contact version of SLot 1. The Slot 2 cartridge may house as many as four processors and an L2 cache. Intel’s Xeon processor uses Slot 2.

Slot A

Developed by AMD, Slot A is mechanically similar to Intel’s Slot 1. However, the electrical requirements are different from Slot 1. AMD’s Athlon processor uses Slot A.

Intel® D850GB Motherboard

The Intel® D850GB Motherboard harnesses the advanced computing power of the
Intel® Pentium® 4 processor. Designed for the new Intel® 850 chipset, the Desktop
Board D850GB utilizes the Pentium 4 processor‘s full bandwidth and performance
with dual RAMBUS* channels and support for Intel® NetBurst™ micro-architecture.
The Intel® D850GB Desktop Board is the newest performance platform solution to
provide unprecedented system efficiency and responsiveness to stay on the cutting
edge of the Internet.

The Intel® D850GB Motherboard supports Intel NetBurst micro-architecture with
dual RDRAM* channels, providing 3.2 GB/second memory bus bandwidth to match
the Pentium 4 processor‘s system bus requirements. The new Intel 850 chipset also
supports system bus speeds of 400 MHz for performance improvements in high-
bandwidth and concurrent applications required for today’s emerging Web
technologies. The Intel® D850GB Motherboard is also designed to enhance overall
system performance with features such as Intel® Rapid BIOS Boot that speeds up
the Power on Self Test (POST), Communications and Networking Riser (CNR)* for
audio, modem, LAN and HPNA support, Ultra ATA/100 disk support; and four USB
ports. This ATX desktop board with five PCI slots, AGP 4X and Instantly Available™
PC (Suspend-to-RAM) is a proven-performance Intel® platform for the Pentium 4

Intel® Desktop Board D850GB Features and Benefits



Support for the Intel® Pentium® 4 Processor

Supports 423-pin Pin Grid Array (PGA) package, and Intel® NetBurst™ micro-architecture which includes 400-MHz system bus.

Intel® 850 Chipset featuring Dual RDRAM* Channel Support

Latest Intel® chipset to support the new Pentium 4 enhanced features. Delivers 3.2 GB/second bandwidth for maximum performance.

Intel® Rapid BIOS Boot

Reduced boot time enables faster system availability.

Universal AGP 4X 1.5V Connector

Supports the latest graphics technology.

Four RDRAM* RIMM Sockets

Supports fast PC800, PC600 RDRAM* memory from 128 MB to 2 GB.

Ultra ATA/100

Faster disk I/O.

Five PCI Slots

Expansion slots for custom system configurations and future add-in card upgrades.

Four USB Ports

Dual-stack rear connectors and header for two front panel USB connectors.

Communication and Networking Riser (CNR) Support

New technology that supports integrated LAN, HPNA, modem or audio cards for overall system cost savings and customization.

ATX Form Factor

Form-factor standard for easy integration.

Instantly Available PC (Suspend-to-RAM)

Power-management mode to reduce PC power consumption. Allows PC to behave like consumer electronic appliance.

Intel® Express Software Suite

Software designed specifically for Intel® desktop boards and ease of integration. Suite includes:

  • Intel® Express Installer
  • Intel® Active Monitor
  • Norton* Internet Security 2000
  • Software Drivers
  • Product Guide
  • Encryption Plus* Secure Export

Hardware Management ASIC

In coordination with Intel Active Monitor, allows remote monitoring of system conditions for lower total cost of ownership.

Three-year Limited Warranty

Expanded investment protection.


Intel 850® chipset

Intel® 82850 Memory Controller Hub (MCH) with AHA (Accelerated Hub Architecture) bus
Intel 82801BA I/O Controller Hub (ICH2) with AHA bus
Intel 82802AB Firmware Hub (FWH)

I/O Controller Hub (ICH2)

ICH2 I/O Controller Hub

Ultra ATA/66/100
Ultra DMA/33
Six PCI request-grant pairs for support of six PCI Bus Masters

I/O Features

Integrated Super I/O LPC bus controller
Five PCI Local Bus slots
Communication and Networking Riser (CNR)* (optional), shared with PCI slot 5
Power Management support for both ACPI 1.0 and APM 1.2
PC 99 and PC 99A Compliance


Two USB controllers with four USB ports

  • Two-port stacked rear connector
  • Header for cabling two ports to the front panel

Firmware Hub

System BIOS

4-Mb Flash EEPROM with Intel/AMI* BIOS featuring Plug and Play, IDE drive auto-configure
Advanced Power Management (APM) 1.2, ACPI 1.0, DMI 2.0, Multilingual support

Intel® Rapid BIOS Boot

Optimized POST delivers faster access to PC from power-on

System Memory

Memory Capacity

Four 184-pin unbuffered RIMM sockets for 128 MB (min) to 2 GB (max) RDRAM

Memory Type

PC600 or PC800 Dual-channel RDRAM

Memory Voltage

2.5 V

Hardware Management Features

Voltage sense to detect out of range values
Fan-sensor inputs used to monitor fan activity
Fan-speed control with temperature

Front Panel Connector

Reset, HD LED, Power LEDs, Power On/Off, Standby header, IR Port, Aux LED

Board Style

ATX 2.03 compliant board size

Board Size


Baseboard Power Requirements

Utilizes new ATX12V spec with these requirements:
+3.3V 20A
+5V 25A
+12V 13A
-12V .8A
+5VSB 1.5A
-5V .3A

Operating Temperature

0° C to +55° C

Storage Temperature

-40° C to +70° C


The form factor of a motherboard determines the specifications for its general shape and size. It also specifies what type of case and power supply will be supported, the placement of mounting holes, and the physical layout and organization of the board. Form factor is especially important if you build your own computer systems and need to ensure that you purchase the correct case and components. earlier). Some of the problems with this form factor mainly arose from the physical size of the board, which is 12″ wide, often causing the board to overlap with space required for the drive bays.

Following the AT form factor, the Baby AT form factor was introduced. With the Baby AT form factor the width of the motherboard was decreased from 12″ to 8.5″, limiting problems associated with overlapping on the drive bays’ turf. Baby AT became popular and was designed for peripheral devices — such as the keyboard, mouse, and video — to be contained on circuit boards that were connected by way of expansion slots on the motherboard. Baby AT was not without problems however. Computer memory itself advanced, and the Baby AT form factor had memory sockets at the front of the motherboard. As processors became larger, the Baby AT form factor did not allow for space to use a combination of processor, heatsink, and fan. The ATX form factor was then designed to overcome these issues


Below is some of the ways in determining if your motherboard is an AT motherboard or an ATX motherboard.

The Keyboard:

AT Motherboard = 5 pin large connector
ATX Motherboard = 6 pin mini connector.

MB Power Connector:

AT Motherboard = Single Row two connectors 5v & 12v
ATX Motherboard = Double row single connector 5v,12v, and 3.3v


The motherboard is the main component found in PC and Macintosh computers. The motherboard is what allows various hardware components to transfer information to each other. As computers advanced, so did motherboards; below is a listing of the various Motherboard form factors.


Full-AT (12″ wide x 13.8″ deep) Matches the original IBM AT motherboard design, which only fits into full size AT or tower cases only, not being produced much any more, if any.

  • This form factor is no longer produced because it cannot be placed into the popular Baby-AT chassis.

Baby-AT (8.57″ wide x 13.04″ deep) Almost the same as the original IBM XT motherboard with modifications in the screw hole position to fit into AT style case, with connections built onto the motherboard to fit the holes in the case.

  • Specific placement of the keyboard and the I/O slots.
  • This board also cannot be placed into the slimline case.

LPX (9.00″ wide x 13.00″ deep) Developed by Western Digital when making motherboards, which was duplicated by many other manufacturers and is no longer made by Western Digital.

  • The LPX motherboard riser card contains all of the expansion slots.
  • Placement of the video, parallel, two serial and PS/2 connections have changed locations.

Full-ATX – (12″ wide x 9.6″ deep) / Mini-ATX – (11.2″ wide x 8.2″ deep) The official specifications were released by Intel in 1995 and was revised to version 2.01 in February 1997. The ATX form factor is an advancement over previous AT style motherboards. Therefore requires a new case design. ATX is not an abbreviation, it is actually a trademark which belongs to Intel.

  • The ATX motherboard has a stacked I/O connector panel mounted on the motherboard.
  • On a socket 7 ATX motherboard, the socket has been placed a further distance from the expansion slots, allowing for long boards to be placed in easier.
  • Single keyed internal power supply connector. This is the Molex power connector, ATX 2.01. Standby voltage needs to be greater than 720 mA. The connector now cannot be placed in improperly. While the Molex power connector allows for 5v and 3.3v to be connected, it is recommended that only a 3.3v be connected to the motherboard.
  • Relocation of the memory and the CPU creating better ventilation and easier upgrade.
  • Power management possible with proper BIOS support.

NLX (Supports motherboards with overall dimensions of 9.0″ x 13.6″ [maximum] to 8.0″ x 10.0″ [minimum]) Implemented in 1998 by Intel and is similar to the LPX form factor; however, includes several new improvements.

  • Support for the Pentium II
  • Support for AGP
  • Support for USB.
  • Support for DIMM.
  • Easier Access to internal components
  • Support for motherboards that can be removed without using tools.

Expansion Slot

A slot located inside a computer on the motherboard or riser board that allows additional boards to be connected to it. Below is a listing of some of the expansion slots commonly found in IBM compatible computers as well as other brands of computers and a graphic illustration of a motherboard and its expansion slots.

Common types of expansion slots:

  • AGP Accelerated Graphics Port
  • AMR Audio/Modem Riser
  • CNR Communication and Network Riser
  • EISA Extended Industry Standard Architecture,
  • ISA Industry Standard Architecture
  • PCI Peripheral Component Interconnect
  • VESA Video Electronics Standard Association


n The chipset is the mother board

n A chipset is a group of microcircuits that orchestrate the flow of data to and from key components of a PC

n Any two boards with the same chipsets the functionally identical

  1. A designated group of microchips that are designed to work with one or more related functions that were first introduced in 1987. When referring the the main motherboard chipset such as the Intel Chipsets, these chipsets will generally include the functions of the CPU, PCI, ISA, USB, etc… An example of an Intel chipset is the i820 or the Intel 820 chipset.
  2. late 1990s, Acer Laboratories (ALI), SIS and VIA Technologies all started developing chipsets for Intel, AMD and Cyrix processors
  3. 1998 PC’s 66MHz system bus finally being overcome., pushing Socket 7 chipsets to 100MHz.
  4. Intel responded with its 440BX, one of many Northbridge/Southbridge architecture.
  5. 1999, its single-minded commitment to Direct Rambus left Intel in the embarrassing position of not having a chipset that supported the 133MHz bus speed of its latest range of processors
  6. 2002 Intel 845d support DDR

Chips or Chips and Technologies is also a computer company. See our chips company information page for additional information about this company.

What is the chipset ?

· Contains the process that Interface bus (FSB)

· Contains the memory controllers

· Bus controllers

· I/O. controllers

· And more

· All of circuits of the mother board are contained within the chipset


An integrated circuit (generally Intel or VIA) that is responsible for the communications between the CPU interface, AGP, PCI and the memory. The Northbridge gets its name for commonly being North of the PCI bus. Below is a graphic illustration of the ASUS P5AD2-E motherboard and some basic explanations of each of the major portions of the motherboard, including the northbridge. As shown in the below picture, it’s common for the northbridge and southbridge to have a heatsink; in addition, the northbridge is usually slightly larger than the southbridge.


An integrated circuit ( generally Intel or VIA ) on the motherboard that is responsible for the hard disk drive controller, I/O controller and integrated hardware such as sound card or video card if present on the motherboard. The Southbridge gets its name for commonly being South of the PCI bus. Below is a graphic illustration of the ASUS P5AD2-E motherboard and some basic explanations of each of the major portions of the motherboard including the southbridge. As shown in the below picture, it’s common for the northbridge and southbridge to have a heatsink; in addition, the northbridge is usually slightly larger than the southbridge

CMOS (complementary metal-oxide semiconductor)

Also known as a RTC/NVRAM or CMOS RAM, CMOS is short for Complementary Metal-Oxide Semiconductor. CMOS is an on-board semiconductor chip powered by a CMOS battery inside IBM compatible computers that stores information such as the system time and system settings for your computer. A CMOS is similar to the Apple Macintosh computer’s PRAM.

Types of CMOS batteries – The following is a listing of the types of batteries found in computers to power the CMOS memory. The most common type of battery is the Coin cell battery (Lithium Battery). The coin cell battery is the size of a dime, as shown below.

Life time of a CMOS battery – The standard lifetime of a CMOS battery is around 10 Years; however, this amount of time can change depending on the use and environment that the computer resides.

CMOS (complementary metal-oxide semiconductor) is the semiconductor technology used in the transistors that are manufactured into most of today’s computer microchips. Semiconductors are made of silicon and germanium, materials which “sort of” conduct electricity, but not enthusiastically. Areas of these materials that are “doped” by adding impurities become full-scale conductors of either extra electrons with a negative charge (N-type transistors) or of positive charge carriers (P-type transistors). In CMOS technology, both kinds of transistors are used in a complementary way to form a current gate that forms an effective means of electrical control. CMOS transistors use almost no power when not needed. As the current direction changes more rapidly, however, the transistors become hot. This characteristic tends to limit the speed at which microprocessors can operate

BIOS (basic input/output system)

BIOS (basic input/output system) is the program a personal computer’s microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer’s operating system and attached devices such as the hard disk , video adapter , keyboard , mouse , and printer .

BIOS is an integral part of your computer and comes with it when you bring it home. (In contrast, the operating system can either be preinstalled by the manufacturer or vendor or installed by the user.) BIOS is a program that is made accessible to the microprocessor on an eraseable programmable read-only memory ( EPROM ) chip. When you turn on your computer, the microprocessor passes control to the BIOS program, which is always located at the same place on EPROM.

When BIOS boots up (starts up) your computer, it first determines whether all of the attachments are in place and operational and then it loads the operating system (or key parts of it) into your computer’s random access memory ( RAM ) from your hard disk or diskette drive.

With BIOS, your operating system and its applications are freed from having to understand exact details (such as hardware addresses) about the attached input/output devices. When device details change, only the BIOS program needs to be changed. Sometimes this change can be made during your system setup. In any case, neither your operating system or any applications you use need to be changed.

Although BIOS is theoretically always the intermediary between the microprocessor and I/O device control information and data flow, in some cases, BIOS can arrange for data to flow directly to memory from devices (such as video cards) that require faster data flow to be effective.

What BIOS Does

The BIOS software has a number of different roles, but its most important role is to load the operating system. When you turn on your computer and the microprocessor tries to execute its first instruction, it has to get that instruction from somewhere. It cannot get it from the operating system because the operating system is located on a hard disk, and the microprocessor cannot get to it without some instructions that tell it how. The BIOS provides those instructions. Some of the other common tasks that the BIOS performs include:

· A power-on self-test (POST) for all of the different hardware components in the system to make sure everything is working properly

· Activating other BIOS chips on different cards installed in the computer – For example, SCSI and graphics cards often have their own BIOS chips.

· Providing a set of low-level routines that the operating system uses to interface to different hardware devices – It is these routines that give the BIOS its name. They manage things like the keyboard, the screen, and the serial and parallel ports, especially when the computer is booting.

· Managing a collection of settings for the hard disks, clock, etc.

The BIOS is special software that interfaces the major hardware components of your computer with the operating system. It is usually stored on a Flash memory chip on the motherboard, but sometimes the chip is another type of ROM.

BIOS uses Flash memory, a type of ROM.

When you turn on your computer, the BIOS does several things. This is its usual sequence:

1. Check the CMOS Setup for custom settings

2. Load the interrupt handlers and device drivers

3. Initialize registers and power management

4. Perform the power-on self-test (POST)

5. Display system settings

6. Determine which devices are bootable

7. Initiate the bootstrap sequence

The first thing the BIOS does is check the information stored in a tiny (64 bytes) amount of RAM located on a complementary metal oxide semiconductor (CMOS) chip. The CMOS Setup provides detailed information particular to your system and can be altered as your system changes. The BIOS uses this information to modify or supplement its default programming as needed. We will talk more about these settings later.

Interrupt handlers are small pieces of software that act as translators between the hardware components and the operating system. For example, when you press a key on your keyboard, the signal is sent to the keyboard interrupt handler, which tells the CPU what it is and passes it on to the operating system. The device drivers are other pieces of software that identify the base hardware components such as keyboard, mouse, hard drive and floppy drive. Since the BIOS is constantly intercepting signals to and from the hardware, it is usually copied, or shadowed, into RAM to run faster

Booting the Computer

Whenever you turn on your computer, the first thing you see is the BIOS software doing its thing. On many machines, the BIOS displays text describing things like the amount of memory installed in your computer, the type of hard disk and so on. It turns out that, during this boot sequence, the BIOS is doing a remarkable amount of work to get your computer ready to run. This section briefly describes some of those activities for a typical PC.

After checking the CMOS Setup and loading the interrupt handlers, the BIOS determines whether the video card is operational. Most video cards have a miniature BIOS of their own that initializes the memory and graphics processor on the card. If they do not, there is usually video driver information on another ROM on the motherboard that the BIOS can load.

Next, the BIOS checks to see if this is a cold boot or a reboot. It does this by checking the value at memory address 0000:0472. A value of 1234h indicates a reboot, and the BIOS skips the rest of POST. Anything else is considered a cold boot.

If it is a cold boot, the BIOS verifies RAM by performing a read/write test of each memory address. It checks the PS/2 ports or USB ports for a keyboard and a mouse. It looks for a peripheral component interconnect (PCI) bus and, if it finds one, checks all the PCI cards. If the BIOS finds any errors during the POST, it will notify you by a series of beeps or a text message displayed on the screen. An error at this point is almost always a hardware problem.

The BIOS then displays some details about your system. This typically includes information about:

· The processor

· The floppy drive and hard drive

· Memory

· BIOS revision and date

· Display

Any special drivers, such as the ones for small computer system interface (SCSI) adapters, are loaded from the adapter, and the BIOS displays the information. The BIOS then looks at the sequence of storage devices identified as boot devices in the CMOS Setup. “Boot” is short for “bootstrap,” as in the old phrase, “Lift yourself up by your bootstraps.” Boot refers to the process of launching the operating system. The BIOS will try to initiate the boot sequence from the first device. If the BIOS does not find a device, it will try the next device in the list. If it does not find the proper files on a device, the startup process will halt. If you have ever left a floppy disk in the drive when you restarted your computer, you have probably seen this message.

The BIOS has tried to boot the computer off of the floppy disk left in the drive. Since it did not find the correct system files, it could not continue. Of course, this is an easy fix. Simply pop out the disk and press a key to continue.

Configuring BIOS

In the previous list, you saw that the BIOS checks the CMOS Setup for custom settings. Here’s what you do to change those settings.

To enter the CMOS Setup, you must press a certain key or combination of keys during the initial startup sequence. Most systems use “Esc,” “Del,” “F1,” “F2,” “Ctrl-Esc” or “Ctrl-Alt-Esc” to enter setup. There is usually a line of text at the bottom of the display that tells you “Press ___ to Enter Setup.”

Once you have entered setup, you will see a set of text screens with a number of options. Some of these are standard, while others vary according to the BIOS manufacturer. Common options include:

· System Time/Date – Set the system time and date

· Boot Sequence – The order that BIOS will try to load the operating system

· Plug and Play – A standard for auto-detecting connected devices; should be set to “Yes” if your computer and operating system both support it

· Mouse/Keyboard – “Enable Num Lock,” “Enable the Keyboard,” “Auto-Detect Mouse”…

· Drive Configuration – Configure hard drives, CD-ROM and floppy drives

· Memory – Direct the BIOS to shadow to a specific memory address

· Security – Set a password for accessing the computer

· Power Management – Select whether to use power management, as well as set the amount of time for standby and suspend

· Exit – Save your changes, discard your changes or restore default settings

Be very careful when making changes to setup. Incorrect settings may keep your computer from booting. When you are finished with your changes, you should choose “Save Changes” and exit. The BIOS will then restart your computer so that the new settings take effect.

The BIOS uses CMOS technology to save any changes made to the computer’s settings. With this technology, a small lithium or Ni-Cad battery can supply enough power to keep the data for years. In fact, some of the newer chips have a 10-year, tiny lithium battery built right into the CMOS chip!

Updating Your BIOS

Occasionally, a computer will need to have its BIOS updated. This is especially true of older machines. As new devices and standards arise, the BIOS needs to change in order to understand the new hardware. Since the BIOS is stored in some form of ROM, changing it is a bit harder than upgrading most other types of software.

To change the BIOS itself, you’ll probably need a special program from the computer or BIOS manufacturer. Look at the BIOS revision and date information displayed on system startup or check with your computer manufacturer to find out what type of BIOS you have. Then go to the BIOS manufacturer’s Web site to see if an upgrade is available. Download the upgrade and the utility program needed to install it. Sometimes the utility and update are combined in a single file to download. Copy the program, along with the BIOS update, onto a floppy disk. Restart your computer with the floppy disk in the drive, and the program erases the old BIOS and writes the new one. You can find a BIOS Wizard that will check your BIOS at BIOS Upgrades.

Major BIOS manufacturers include:

· American Megatrends Inc. (AMI)

· Phoenix Technologies

· ALi

· Winbond

As with changes to the CMOS Setup, be careful when upgrading your BIOS. Make sure you are upgrading to a version that is compatible with your computer system. Otherwise, you could corrupt the BIOS, which means you won’t be able to boot your computer. If in doubt, check with your computer manufacturer to be sure you need to upgrade.

BIOS Beep Codes

  • Whenever a recoverable error occurs during POST, the BIOS displays an error message describingthe problem (see Table 82).
  • The BIOS also issues a beep code (one long tone followed by two short tones) during POST if the video configuration fails (a faulty video card or no card installed)

or if an external ROM module does not properly checksum to zero.

  • An external ROM module (for example, a video BIOS) can also issue audible errors, usually consisting of one long tone followed by a series of short tones.
  • For more information on the beep codes issued, check the documentation for that external device.
  • There are several POST routines that issue a POST terminal error and shut down the system if they fail.
  • Before shutting down the system, the terminal-error handler issues a beep code signifying the test point error, writes the error to I/O port 80h, attempts to initialize the video and writes the error in the upper left corner of the screen (using both monochrome and color adapters).

Table 82. Beep Codes

Beep Description

1 Refresh failure

2 Parity cannot be reset

3 First 64 KB memory failure

4 Timer not operational

5 Not used

6 8042 GateA20 cannot be toggled

7 Exception interrupt error

8 Display memory R/W error

9 Not used

10 CMOS Shutdown register test error

11 Invalid BIOS (e.g. POST module not found, etc.)

POST (Power on Self Test)

The computer POST (Power on Self Test) tests the computer, insuring that it meets the necessary system requirements and that all hardware is working properly before starting the remainder of the boot process. If the computer passes the POST the computer will have a single beep (with some computer BIOS manufacturers it may beep twice) as the computer starts and the computer will continue to start normally. However, if the computer fails the POST, the computer will either not beep at all or will generate a beep code, which tells the user the source of the problem.

The steps of a POST

Each time the computer boots up the computer must past the POST. Below is the common steps a POST performs each time your computer starts.

1. Test the power supply to ensure that it is turned on and that it releases its reset signal.

2. CPU must exit the reset status mode and thereafter be able to execute instructions.

3. BIOS checksum must be valid, meaning that it must be readable.

4. CMOS checksum must be valid, meaning that it must be readable.

5. CPU must be able to read all forms of memory such as the memory controller, memory bus, and memory module.

6. The first 64KB of memory must be operational and have the capability to be read and written to and from, and capable of containing the POST code.

7. I/O bus / controller must be accessible.

8. I/O bus must be able to write / read from the video subsystem and be able to read all video RAM.

An irregular POST is a beep code that is different from the standard one or two beeps. This could be either no beeps at all or a combination of different beeps indicating what is causing the computer not to past the POST.

9. If you’re receiving an irregular POST contains all the steps a user can do to resolve the issue or help determine what hardware has failed in the computer so it can be replaced. If you’re getting a beep code the remainder of this page contains a listing of each of the major manufacturers beep codes and what they each mean

AMI BIOS beep codes

Below are the AMI BIOS Beep codes that can occur. However, because of the wide variety of different computer manufacturers with this BIOS, the beep codes may vary.

BIOS Setup Program


The BIOS Setup program can be used to view and change the BIOS settings for the computer. The BIOS Setup program is accessed by pressing the <F2> key after the Power-On Self-Test (POST) memory test begins and before the operating system boot begins. The menu bar is shown below.

Maintenance Main Advanced Security Power Boot Exit

Table 58 lists the BIOS Setup program menu features.

Table 58. BIOS Setup Program Menu Bar

Maintenance Main Advanced Security Power Boot Exit


passwords and

BIS credentials

and enables





resources for







through the




and security






Selects boot

options and

power supply


Saves or


changes to



BIOS Security Features

· The BIOS includes security features that restrict access to the BIOS Setup program and who can

boot the computer. A supervisor password and a user password can be set for the BIOS Setup

program and for booting the computer, with the following restrictions:

· The supervisor password gives unrestricted access to view and change all the Setup options in

the BIOS Setup program. This is the supervisor mode.

· The user password gives restricted access to view and change Setup options in the BIOS Setup

program. This is the user mode.

· If only the supervisor password is set, pressing the <Enter> key at the password prompt of the

BIOS Setup program allows the user restricted access to Setup.

· If both the supervisor and user passwords are set, users can enter either the supervisor

password or the user password to access Setup. Users have access to Setup respective to

which password is entered.

· Setting the user password restricts who can boot the computer. The password prompt will be

displayed before the computer is booted. If only the supervisor password is set, the computer

boots without asking for a password. If both passwords are set, the user can enter either

password to boot the computer.


Supplies power throughout the computer. Power supplies convert potentially lethal 110-115 or 220-230 volt alternating current (AC) into a steady low-voltage direct current (DC) usable by the computer. A power supply is rated by the number of watts it generates.

WARNING: Do not open the power supply, it contains capacitors which can hold Electricity (WHICH CAN KILL) even if the computer is power off for a week, if not longer. If you do open it, WHICH IS NOT RECOMMENDED, take all precautions and ensure you work with one arm behind your back to direct the electricity away from the heart. Also ensure that you have no jewelry on (such as a watch or rings). However, again, THIS IS NOT RECOMMENDED, and still cannot protect you 100% and is still potentially dangerous. Because of these precautions, no extensive information will be found on this page about opening power supplies.


Currently in the industry there are eight power supply form factors. Each of these form factors can have various amounts of configurations and power output levels.

Baby AT



The below illustration is the typical female connector which would be used to connect to a device such as a CD-ROM or Hard Drive. This connector is refereed to as a large Molex connector. Additional to these types of connectors you may also find a small Molex which is generally used for the floppy disk drive.


Wire Color















Pin Number






“Power Good”



Red (XT No Wire)

+5V DC




+12V DC




-12V DC
























-5V DC




+5V DC




+5V DC



Power management was designed for convenience as it easier to have your computer go into power standby and be able to press a key on your keyboard or move your mouse and instantaneously be back where you were and for saving power. This is especially important on portable computers when using the battery as your main power source

Power Management Methods

l Advanced Power Management (APM)

l AT Attachment (ATA) for IDE drives

l Display Power Management Signaling (DPMS) standards for monitors and video cards

l Advanced Configuration and Power Interface (ACPI)

Power Management Features

l Green timer on the motherboard

l Doze time

l Standby time

l Suspend time

l Hard drive standby time

Power Management is a way for the computer to save power by turning off certain features of the computer such as the monitor, hard disk drives and other computer peripherals.

APM, or Advanced Power Management, is an Application Program Interface, or API, developed by Microsoft and Intel which allows computer and BIOS manufacturers to include Power Management into their BIOSes.

In the near future, ACPI, or Advanced Configuration and Power Interface, developed by Microsoft, Intel and Toshiba will be used which will essentially allow computers equipped with future operating systems and capable hardware to shutdown the computer temporarily. When the computer is turned back on or a button is pressed, the computer will immediately come on within a few seconds.

The loss of electricity to a computer, peripherals and/or other electronic devices. When a power failure occurs, any data currently in a temporary storage, such as in the computer’ memory, is immediately lost and unrecoverable. Power failures may also cause data corruption and, in some cases, hardware to go bad

Also known as a power cable, mains cable or flex a power cord is the primary cable that provides power to the computer, printer, monitor, and components within a computer. The image to the left is an example of the power cord that is commonly used with computers, monitors, printers, and many other peripherals.

Switched-Mode Power Supply, SMPS is a type of power supply that uses a switching regulator to control and stabilize the output voltage by switching the load current on and off. These types of power supplies offer a greater power conversion and reduce the overall power loss.

The power supply of a desktop PC, sometimes also referred to as a Silverbox (Figure 1), supplies all the power needed in a desktop PC. During normal operation a number of DC power supply voltages have to be provided: a 12, 5 and 3.3V supply voltage, a 5V standby supply, and a low current, less accurate –12V supply. The 12, 5 and 3.3V supplies must each be capable of supplying 20A or more with a voltage accuracy of ±5%. The average efficiency per today at maximum load is about 70 percent, so when 300W is delivered to the load about 100W of power is wasted and converted into heat, which is subsequently removed using heat sinks and fans.

Alternating current (AC)

Cycles back and forth


Direct current (DC)

Travels in only one direction, from hot to ground

Required by most electronic devices

Computer power supply functions as both a transformer and rectifier

Potential Outcomes of a Faulty Power Supply

l Memory errors

l Data errors

l System hangs

l System reboots

l Damage to a motherboard or other component

Categories: EC1003 UNIT V
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