Power-on self-test

When power is turned on, POST (Power-On Self-Test) is the diagnostic testing sequence that a computer's basic input/output system (or "starting program") runs to determine if the computer keyboard,
random access memory, disk drives, and other hardware are working correctly.
If the necessary hardware is detected and found to be operating properly, the computer begins to boot. If the hardware is not detected or is found not to be operating properly, the BIOS issues an error message which may be text on the display screen and/or a series of coded beeps, depending on the nature of the problem.The pattern of beeps may be a variable numbers of short beeps or a mixture of long and short beeps, depending on what type of BIOS is installed.
The patterns of beeps contain messages about the nature of the problem detected. For example, if the keyboard is not detected, a particular pattern of beeps will inform you of that fact. An error found in the POST is usually fatal (that is, it causes current program to stop running) and will halt the boot process, since the hardware checked is absolutely essential for the computer's functions.

General internal workings

• verify the integrity of the BIOS code itself

• determine the reason POST is being executed

• find, size, and verify system main memory

• discover, initialize, and catalog all system buses and devices

• pass control to other specialized BIOS-es (if and when required)

• provide a user interface for systems configuration

• identify, organize, and select which devices are available for booting

• construct whatever system environment that is required by the target OS

Fundamental structure/Error reporting/Original IBM POST error codes

• 1 short beep - Normal POST - system is OK

• 2 short beeps - POST error - error code shown on screen

• No beep - Power supply or system board problem

• Continuous beep - Power supply, system board, or keyboard problem

• Repeating short beeps - Power supply or system board problem or keyboard

• 1 long, 1 short beep - System board problem

• 1 long, 2 short beeps - Display adapter problem (MDA, CGA)

• 1 long, 3 short beeps - Enhanced Graphics Adapter (EGA)

• 3 long beeps - 3270 keyboard card

POST AMI BIOS beep codes

• 1 - Memory refresh timer error

• 2 - Parity error in base memory (first 64 KB block)

• 3 - Base memory read/write test error

• 4 - Mother board timer not operational

• 5 - Processor error

• 6 - 8042 Gate A20 test error (cannot switch to protected mode)

• 7 - General exception error (processor exception interrupt error)

• 8 - Display memory error (system video adapter)

• 9 - AMI BIOS ROM checksum error

• 10 - CMOS shutdown register read/write error

• 11 - Cache memory test failed

POST beep codes on CompTIA A+ Hardware Core exam Beeps Meaning

• Steady,short beeps Power supply may be bad

• Long continuous beep tone Power supply bad or not plugged into correctly

• Steady, long beeps Power supply bad

• No beep Power supply bad, system not plugged in, or power not turned on

• One long, two short beeps Video card failure

IBM POST diagnostic code descriptions

• 100 to 199 - System boards

• 200 to 299 - Memory

• 300 to 399 - Keyboard

• 400 to 499 - Monochrome display

• 500 to 599 - Color/graphics display

• 600 to 699 - Floppy-disk drive or adapter

• 700 to 799 - Math coprocessor

• 900 to 999 - Parallel printer port

• 1000 to 1099 - Alternate printer adapter

• 1100 to 1299 - Asynchronous communication device, adapter, or port

• 1300 to 1399 - Game port

• 1400 to 1499 - Color/graphics printer

• 1500 to 1599 - Synchronous communication device, adapter, or port

• 1700 to 1799 - Hard drive and/or adapter

• 1800 to 1899 - Expansion unit (XT)

• 2000 to 2199 - Bisynchronous communication adapter

• 2400 to 2599 - EGA system-board video (MCA)

• 3000 to 3199 - LAN adapter

• 4800 to 4999 - Internal modem

• 7000 to 7099 - Phoenix BIOS chips

• 7300 to 7399 - 3.5-inch disk drive

• 8900 to 8999 - MIDI adapter

• 11200 to 11299 - SCSI adapter

• 21000 to 21099 - SCSI fixed disk and controller

•  21500 to 21599 - SCSI CD-ROM system

Macintosh POST

• 1 beep = No RAM installed/detected

• 2 beeps = Incompatible RAM type installed (for example, EDO)

• 3 beeps = No RAM banks passed memory testing

• 4 beeps = Bad checksum for the remainder of the boot ROM

• 5 beeps = Bad checksum for the ROM boot block

• 1 beep = no RAM installed

• 2 beeps = incompatible RAM types

• 3 beeps = no good banks

• 4 beeps = no good boot images in the boot ROM (and/or bad sys config block)

• 5 beeps = processor is not usable

On power up, the main duties of POST are handled by the BIOS, which may hand some of these duties to other programs designed to initialize very specific peripheral devices, notably for video and SCSI initialization. These other duty-specific programs are generally known collectively as option ROMs or individually as the video BIOS, SCSI BIOS, etc.

The principal duties of the main BIOS during POST are as follows:

The BIOS will begin its POST duties when the CPU is reset. The first memory location the CPU tries to execute is known as the reset vector. In the case of a hard reboot, the north-bridge will direct this code fetch (request) to the BIOS located on the system flash memory. For a warm boot, the BIOS will be located in the proper place in RAM and the north-bridge will direct the reset vector call to the RAM.
During the POST flow of a contemporary BIOS, one of the first things a BIOS should do is determine the reason it is executing. For a cold boot, for example, it may need to execute all of its functionality. If, however, the system supports power savings or quick boot methods, the BIOS may be able to circumvent the standard POST device discovery, and simply program the devices from a reloaded system device table.
The POST flow for the PC has developed from a very simple, straightforward process to one that is complex and convoluted. During POST, the BIOS must integrate a plethora of competing, evolving, and even mutually exclusive standards and initiatives for the matrix of hardware and OSes the PC is expected to support. However, the average user still knows the POST and BIOS only through its simple visible memory tests and setup screen.
In the case of the IBM PC compatible machines, the main BIOS is divided into two basic sections. The POST section, or POST code, is responsible for the tasks mentioned above, and the environment POST constructs for the OS is known as the run-time code, the run-time BIOS, or the run-time footprint. Primarily these two divisions can be distinguished in that POST code should be flushed from memory before control is passed to the target OS while the run-time code remains resident in memory. This division may be a misleading oversimplification, however, as many Run-time functions are executed while the system is Posting.
The original IBM BIOS reported errors detected during POST by outputting a number to a fixed I/O port address, 80. Using a logic analyzer or a dedicated POST card, an interface card that shows port 80 output on a small display, a technician could determine the origin of the problem. (Note that once an operating system is running on the computer, the code displayed by such a board is often meaningless, since some OSes, e.g. Linux, use port 80 for I/O timing operations.) In later years, BIOS vendors used a sequence of beeps from the motherboard-attached loudspeaker to signal error codes.
These POST beep codes are covered specifically on the CompTIA A+ Core Hardware Exam:

Apple's Macintosh computers also perform a POST after a cold boot. In the event of a fatal error, the Mac will not make its start-up chime.
Old World Macs (until 1998)
Macs made prior to 1998, upon failing the POST, will immediately halt with a "death chime," which is a sound that varies by model; it can be a beep, a car crash sound, the sound of shattering glass, a short musical tone, or more. On the screen will be the Sad Mac icon, along with two hexadecimal strings, which can be used to identify the problem.
New World Macs (1998-1999)
When Apple introduced the iMac in 1998, it was a radical departure from other Macs of the time. The iMac began the production of New World Macs, as they are called; New World Macs, such as the iMac, Power Macintosh G3 (Blue & White), Power Mac G4 (PCI Graphics), PowerBook G3 (bronze keyboard), and PowerBook G3 (FireWire), load the Mac OS ROM from the hard drive. In the event of a fatal error, they give these beeps:
New World Macs (1999 onward) and Intel-based Macs
The beep codes were revised in October 1999, and have been the same since. In addition, on some models, the power LED would flash in cadence.

BIOS

What is BIOS?
BIOS or Basic Input/Output System is the first program accessed by the processor during start up to ensure that all the other basic programs, hard drives, ports, peripherals and the central processing unit are in good working condition. BIOS are different from the computer's operating system. The operating system resides in the hard drive and provides the user interface that can be seen on the screen after start up. The BIOS program, on the other hand, can be found right in a flash memory chip or ROM located in the motherboard. It is the basic requirement for booting a computer.
BIOS Functions
BIOS have several functions in a computer but its most important task is to load the operating system. BIOS provide the microprocessor its first instructions upon activating the computer. The instructions of the BIOS to the microprocessor during start up are the following: power on self test which tests the operating status of all the hardware in the computer, activation of other BIOS chips in some other computer components like SCSI and graphics cards, checking and management of computer peripherals through low level routines during the start-up process, and management of clock, hard drive and other settings.
BIOS Sequence
The usual sequence of the BIOS program during start up begins with checking the CMOS setup for any customized settings, loading the device drivers and interrupt handlers of various computer hardware, initializing power management and registers, performing the self test for power, displaying the system settings, determining the bootable devices in the computer, and initiating the boot sequence.
Changing Settings through CMOS
To change the settings in a CMOS setup, a certain key or a certain combination of keys must be pressed during the initial start up sequence. The instructions for this can usually be found at the bottom of the first screen display during the start up process. Upon entering the CMOS set up, several options are available to the user. Setting the system date and time as well as changing the boot sequence, plug and play settings, driver configurations, memory settings, password settings, and power settings are just some of the settings that can be changed on this page.
Updating BIOS
BIOS, especially on older computers, can be updated from time to time. This is so the BIOS program can recognize new devices that have just been recently manufactured. To upgrade or change a computer's BIOS, a special program from the BIOS manufacturer is needed. The BIOS update used must match the original BIOS variant.
The update is done by checking BIOS revision and date information provided on the screen during start up and comparing this with the update list in the BIOS manufacturer's website. The upgrade usually comes with a utility program but sometimes the update can be downloaded separately. This utility program and update must be copied into a floppy disk and inserted into the disk drive the next time your computer boots. This will erase the old BIOS program and install the new one.

Common manufacturers

American Megatrends

Insyde Software

Phoenix Technologies

Byosoft
POST
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. The step by step procedure that a POST performs each time your computer starts is given below.
Test the power supply to ensure that it is turned on and that it releases its reset signal.
CPU must exit the reset status mode and thereafter be able to execute instructions.
BIOS checksum must be valid, meaning that it must be readable.
CMOS checksum must be valid, meaning that it must be readable.
CPU must be able to read all forms of memory such as the memory controller, memory bus, and memory module.
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.
I/O bus / controller must be accessible.
I/O bus must be able to write / read from the video subsystem and be able to read all video RAM.
If the computer does not pass any of the above tests, your computer will receive an irregular POST. 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 that the computer failed in testing POST.
BIOS 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

AMI BIOS beep codes
Beep Code Descriptions

1 short DRAM refresh failure
2 short Parity circuit failure
3 short Base 64K RAM failure
4 short System timer failure
5 short Process failure
6 short Keyboard controller Gate A20 error
7 short Virtual mode exception error
1 long, 3 short Conventional/Extended memory failure

AWARD BIOS beep codes
Beep Code Description
1 long, 2 short :-Indicates a video error has occurred and BIOS initialize the video screen to display additional information
Any other beep(s):- RAM problem.

IBM BIOS beep codes
Beep Code Description

No Beeps No Power, Loose Card, or Short.
1 Short Beep Normal POST, computer is ok.
2 Short Beep POST error, review screen for error code.
Continuous Beep No Power, Loose Card, or Short.
Repeating Short Beep No Power, Loose Card, or Short.
One Long and one Short Beep Motherboard issue.
One Long and Two Short Beeps Video (Mono/CGA Display Circuitry) issue.
One Long and Three Short Beeps Video (EGA) Display Circuitry.
Three Long Beeps Keyboard / Keyboard card error.
One Beep, Blank or Incorrect Display Video Display Circuitry.

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.

BIOS Troubleshooting
Because the BIOS is the essential "glue" that joins hardware to the operating system, you need to know how to deal with errors. Follow these steps to solve BIOS problems.
Incorrect CMOS Configuration
If the system can't start after a BIOS upgrade or a battery replacement, the CMOS might be corrupted. Re-enter the correct settings, save changes, and restart. An onscreen error message will usually indicate a CMOS problem. Otherwise, the settings might have been adjusted by a user. Try using the BIOS Setup auto-configure options, double-check drive configurations, save changes, and restart.
Incorrect Flash BIOS or Failed Update
If you use the wrong flash BIOS file to update your BIOS, or if the update process doesn't finish, your system can't start. You might need to contact the system or motherboard maker for service. Some BIOSes contain a "mini-BIOS" that can be reinstalled from a reserved part of the chip. Systems with this feature have a jumper on the motherboard called the "flash recovery" jumper. Micro Firmware's Web site lists popular motherboards using Phoenix BIOSes that have this feature.
To use this feature, download the correct flash BIOS, make the floppy disk, and take it to the computer with the defective BIOS. Set the jumper to Recovery, insert the floppy disk, and rerun the setup process. Listen for beeps and watch for the drive light to run during this process, because the video won't work. Turn off the computer, reset the jumper to Normal, and restart the computer.
If the update can't be installed, your motherboard might have a jumper that writes-protects the flash BIOS. Check the manual to see if your system has this feature. To update BIOS on a system with a write protected jumper, you must
1Disable the write-protection.
2.Perform the update.
3.Re-enable the write-protection to keep unauthorized people from changing the BIOS.
Summary
The BIOS contains a POST (power on self test) routine that tests memory, video, hard drives, floppy disk drives, and other important system components.
The BIOS also contains a bootstrap program that locates the operating system after the POST and transfers control to it.
The BIOS uses three methods to report errors: beep codes, onscreen error messages, and BIOS POST codes.
The BIOS contains tables of supported devices and options; the CMOS chip is used to store the options chosen with the BIOS setup program.
The CMOS chip is battery-backed.
You must verify correct floppy disk drive and hard drive configurations before a system can be started. These settings are found in the standard CMOS setup screen.
By making adjustments to other BIOS screens, you can adjust the performance of the system, configure the system for compatibility with Windows PnP-compatible boards, adjust or disable built-in ports, and control power management.
A BIOS needs to be upgraded when you want to use new hardware, new software, or new features not included in the current BIOS.
BIOS upgrades can be performed with software (flash BIOS) or by replacing the chip.

Complementary Metal Oxide Semiconductor

Complementary Metal Oxide Semiconductor(CMOS) is a small portion of battery powered memory on the motherboard that contains system settings like types of drives, device types in the system, which drive to start up from etc.
The battery used is a 3volt battery.
CMOS and BIOS are often interchanged although they are different things. Think of the BIOS as the skeleton frame upon which the CMOS settings hang.
All computer memory forgets everything it holds when power to it is shut off. If the power was totally shut off to your CMOS, your computer would forget its start up settings, and you’d have to re-enter these settings every time you started your computer! Fortunately this is not the case as your CMOS always receives enough power to remember its settings, even when your computer is off. How? It is powered by a small lithium battery on your motherboard. Lithium batteries are designed to last years, and often outlive the usefulness of the computer they reside in. If you keep a computer long enough, you will have to replace the battery. This is usually an easy task. Just lift the retaining clip, pop out the old battery and put in a new one. Make sure your computer is off though, and beware of static discharge! After you replace the battery, you WILL HAVE TO re-enter all startup settings into CMOS setup.
It is a good idea to enter the CMOS setup and write down the information it contains. Unless you are fairly knowledgeable in computer support, have original manuals or like frustrating experiences, it is a good idea to keep the CMOS information on paper in case it gets erased.
HOW TO GET INTO THE CMOS?
Computers differ on how to enter setup. Normally when you start your computer, it will say something like "Hit or to enter setup. Based on different company or model the cmos entering key also varies " Take note of what key (or combinations of keys to hit. You can safely look around the setup program. If you accidentally change something, just exit without saving
What is CMOS Setup?
Various devices are attached to a computer. These devices have got various parameters such as IRQ settings, DMA channel settings, etc. Thus this information about the devices or peripherals attached to the computer must be known at the time of startup. These parameters are manually set if the devices are of older types that are non-plug-n-play. But if these devices are plug-n-play then the parameters are detected automatically. This information about the devices is to be stored or else it has to be set every time the machine is started. So this information is set and stored in the CMOS setup.
The CMOS has got a jumper. This jumper is used only for clearing the data stored in the CMOS.
Setting up CMOS setup.
The listing below is showing all the information’s stored into the BIOS;
· Time and Date
· Number of Floppy Disk Drives
· Floppy Disk Drives information’s (size, number of track, sectors, head, etc)
· Number of Hard Disk Drives
· Hard Disk Drives information’s (size, number of track, sectors, head, mode, etc)
· Number of CD-ROM Drives
· CD-ROM Drives information’s (operating mode, etc)
· Boot sequence ( Enable the user to decide what disk will be checked first when booting)
· Cache Memory information’s (size, type, timing, etc)
· Main Memory Information’s (size, type, timing, etc)
· ROM Shadowing information’s (Enabling or disabling of Video and System ROM shadow)
· Basic Video mode information’s (EGA, VGA, etc)
· Setting of PCI and ISA slots
· AGP Port Settings (aperture size, etc)
· Virus Protection Warning
· Setting of COM Ports (Enabling or disabling of Com port 2 for instance)
· Password Protection (enable the user to set his password)
· Energy saving information’s (snooze modes for the HDD and monitor)
Depending on your BIOS type there could be many a lot of other information not listed above that can possibly be stored in the BIOS memory. Note that some of the information in the above list may not be a part of the BIOS installed on your computer.

Motherboard

A computer motherboard is the most important part of a computer.
It is the main printed circuit board (PCB) in the computer and is sometimes referred to as the system board or mainboard.
The motherboard itself is just a piece of fiberglass. It's actually the hardware mounted on it that does all the work in the computer.
The motherboard connects directly or indirectly to every other part of the computer.
Its dimensions vary with the size of the system for which it was made. There are fine copper traces etched onto the board which forms the bus.
The bus carries power and information between the components on the motherboard.
Numerous tiny holes are drilled in the bus on the motherboard into which chips, sockets and other electronic components are installed.
These electronic components are held in place by soldered joints on the underside of the board.
There are also other holes drilled into the motherboard to accept spacers and screws for securing the motherboard to the case.
The evolution of the motherboard has caused more devices to be integrated into the motherboard.



Typical Motherboard Diagram
The parts of the computer motherboard such as RAM and CPU that are more subject to change, have been integrated into sockets so that they can be easily removed and replaced for upgrading.
You will encounter many different types and sizes of motherboards which will be determined by its form factor.
The form factor determines the size and shape of the mainboard and also dictates what kind of case it will fit into.
Listed below are the different types of form factors.
PC/XT - Although it wasn't the first PC, it had many features that were not available with previous PC designs. One such feature was that it was the first computer to have a hard drive.
It also had a large computer motherboard that was installed into a full size horizontal or desktop case.
Full-Size AT - The full-size AT mainboards were large in order to accommodate a lot of circuitry and could be installed in full-size AT desktop and tower cases. At present, full-size AT motherboards are no longer produced.
Baby-AT - Between 1983 to 1986, Baby-AT form factor became the most popular computer motherboard because it was able to fit into a number of different case designs. Today, you may still be able to get motherboards of this design.
In 1996, the Baby-AT was replaced by the ATX design.
LPX - This board was a semi-proprietary motherboard design which was difficult to repair and upgrade. Also, replacement parts for upgrades were expensive thus making it more economical to purchase a brand new non-proprietary design.
ATX - This design improved upon the Baby-AT and the LPX designs. Its physical dimensions are approximaely 12" x 9.6". This design is not compatible with AT designs because the motherboard is turned sideways in the case and has a different power supply connector.
Micro ATX - This is a smaller version of the ATX form factor. Its physical dimensions are approximately 9.6" x 9.6".
All form factors that precede the ATX are now obsolete. A new form factor called BTX is now emerging. There will be three basic sizes:
picoBTX - 7.9" x 10.4".
microBTX - 10.3" x 10.4".
BTX - 12.7" x 10.4".
NOTE: Today, the ATX is the most popular design of the newer motherboards and it is easily upgradeable.
Computer motherboard designs are constantly changing. Listed below are the major components of the motherboard:
BIOS:
Another important component is the basic input/output system (BIOS) chip which contains startup programs such as the power on/self-test (POST) and drivers of the computer.
This chip controls communication between the systems hardware and operating system. BIOS can also be referred to as firmware.
Expansion Slots:
Expansion slots enable the CPU to communicate with the peripheral devices which expand the capability of the computer.
Different cards can be plugged into these slots to enhance the computer such as video cards to improve graphics and sound cards to provide better audio.
Battery:
This battery is referred to as CMOS battery and is responsible for keeping the time and date. It usually has a life span of about 3 to 4 years.
Memory:
In a computer system, the CPU needs information and instructions to perform properly. This information and instructions for the CPU are stored in Random Access Memory (RAM). This memory is sometimes referred to as Primary Memory or Main Memory.
Ports:
Ports allow external devices to be connected to the computer motherboard. There are different types of ports located on the motherboard such as parallel, serial, universal serial bus (USB) and SCSI (small computer system interface).
Until up to a few years ago, printers were connected to parallel ports but now they are being replaced with the faster USB port. Low speed peripherals such as modems, mice and some scanners were connected to the serial port.
Again, this port is being replaced by the USB port which can support up to 127 devices. The SCSI bus can also support a number of peripherals such as hard disks, tape drives, CD-ROM drives, scanners, etc.
Power Connector:
This is a 20-pin male connector located on the computer motherboard. The power supply is plugged into this connector which supplies power for the motherboard, its components and some peripherals.
Most new motherboards now come with a 24-pin connector. Older motherboards with 20-pin connectors can still be used with a 24-pin power supply since this 24-pin connector can be separated into 20-pin and 4-pin connectors.
Integrated Graphics and Audio:
Today, most of the motherboards manufactured include integrated graphics, audio and LAN.
Hard Drive Data Transfer Modes-(Interface):
Motherboards are designed to provide different data transfer rates. First time computers used the UDMA/33 interface but this was increased to UDMA/66 which doubled the data-transfer rate.
The data transfer rate of a hard drive is the time used to read/write information. This interface mode was upgraded to UDMA/100 and then finally to UDMA/133.
These characteristics apply to Parallel ATA hard drives. For a long time, the UDMA/133 remained the fastest interface until the inception of the Serial ATA drive which has a data transfer rate of 150MBS/sec. These have now improved to data transfer rates of 300MBS/sec.
These hard drives can be operated in different modes called RAID (Redundant Array of Independent Disks). RAID requires more than one hard drive.
This provides speed by writing/reading information to more than one drive simultaneously - called 'striping' (RAID, 0).
Another feature is data security or 'mirroring' which duplicates data on both hard drives (RAID,1).

BIOS Problems

General BIOS Problems

Problem: The BIOS fails to detect the hard disk(s), CD-ROM, floppy drive, etc.

Cause: All of a sudden, hard drives and floppies disappear from the list of devices, or you cannot boot because the BIOS declares that you have no hard drive!

Solution: The most common reason for this error is a bad or loose­ly connected cable or incorrect jumper settings on the device. Check all the cable connections to the device. Ensure that the data cable and the power cable are properly plugged in both to the device and to the motherboard. Next, check the jumper settings. If two disks are connected to a single port, make sure one is set to Master and the other to Slave. Also check the BIOS setup program and ensure that IDE controllers are enabled. Go to the Integrated Peripherals menu and confirm that the Primary and Secondary Channels are enabled. If you are not comfortable changing indi­vidual values, reset the settings using the “Load Fail-safe (or Factory) Defaults” option.

Problem: After powering off the PC and switching it back on after a few hours, the time has changed

Cause: The CMOS battery powers the real-time clock. This symp­tom indicates that the battery is dying. In rare cases, it could also mean there’s a problem with the battery port of the CMOS. Solution: Replace the battery. If the symptom persists, there’s a good chance that the battery port is damaged. In this latter case, you may need to replace the motherboard! Get it checked by a computer technician first.

Problem: An error message says there is a problem with IRQ, I/Oport, DMA configuration or resource allocation, and refers totroubleshooting the BIOS

Cause: The BIOS configures and allocates resources to the IRQ,and I/O ports. In most BIOSes, this allocation cannot be changed or modified by the user. Some BIOSes may provide a “soft menu” to change these allocations.

Solution: It’s preferable to get the BIOS checked by a computer engineer. Use the “Load Fail-safe (Factory) Defaults” options in the setup menu. If a soft menu is available, ensure you read up the associated documentation before changing any settings.

Problem: An error message asks to update the BIOS

Cause: The BIOS firmware does not support the device without an update.

Solution: See the Updating the BIOS section

BIOS Beep Codes

BIOS Beep Codes

When your system has a problem that won’t let it start up proper­ly, the first thing you will hear is warning beeps. These could be because of hardware or even because of the BIOS itself.

Unfortunately, beep codes are not standardized across BIOS vendors and motherboard manufacturers. Below are mentioned the beep codes, along with the possible problem that could be causing the beep, and some suggestions towards resolution. These are for two popular BIOS vendors—AMI and Award. If your BIOS is from any other vendor, you will need to refer to the motherboard manufacturer’s or the BIOS vendor’s manual for details.

Also, motherboard manufacturers may modify the beep codes to their convenience and not maintain consistency. Keep an open mind when you decipher the beep, and don’t get into a tizzy if the codes don’t match what is in here or in the BIOS vendor’s manual! You should always try and contact the manufacturer to get the correct beep codes.

AMIBIOS (American Megatrends Inc.)

One beep: RAM failure

Problem: Motherboard problem or failed RAM.

Solution: Troubleshoot the motherboard and/or the RAM.

Two beeps: Parity Circuit Failure

Problem: Motherboard problem or failed RAM.

Solution: Troubleshoot the motherboard and/or the RAM.

Three beeps: Base 64K RAM failure

Problem: There is a failure within the first 64K of memory.

Solution: Troubleshoot the motherboard and/or the RAM.

Four beeps: System Timer Failure

Problem: One or more of the system timers on the motherboard has failed; usually indicates motherboard failure.

Solution: Troubleshoot the motherboard. You may need to replace it.

Five beeps: Processor Failure

Problem: The processor is generating an error condition. This does not mean that the processor is not working—with a dead proces­sor, the computer won’t boot at all.

Solution: Check if the processor is overheating, and whether it is set correctly on the motherboard. Troubleshoot the motherboard.

Six beeps: Keyboard controller or gate A20 failure

Problem: Keyboard, keyboard controller or motherboard error.

Solution: Check if the keyboard is connected properly. Use anoth­er keyboard to see if the problem persists. If it does, look for the keyboard controller chip on the motherboard and see if it is seat­ed properly and that it is not damaged. If the problem continues, troubleshoot the motherboard.

Seven beeps: Virtual mode exception error

Problem: This error is reported when testing the processor’s virtu­al mode. Solution: Troubleshoot the motherboard/processor. Verify that all jumpers are properly configured.

Eight beeps: Display memory read/write failure

Problem: The BIOS is not able to read/write the display card’s memory.

Solution: Troubleshoot the motherboard and/or display card.

Nine beeps: BIOS’ ROM checksum failure

Problem: The BIOS CMOS chip is most likely defective. May also be a problem with the motherboard.

Solution: The CMOS chip can be replaced, but replacing the moth­erboard is simpler and more cost-effective.

10 beeps: CMOS shutdown register read/write error

Problem: A motherboard component is creating an error when interacting with the CMOS.

Solution: Troubleshoot the motherboard and verify that all com­ponents are properly set up and configured.

11 beeps: Cache memory error

Problem: There is an problem with the processor’s L2 cache.

Solution: Verify that the L2 cache chip is inserted correctly. Verify that all connections inside the PC are correct. Replace the cache module if the problem persists.

Continuous beeps: Video / Memory problem

Problem: A problem with the RAM, display card or motherboard.

Solution: Troubleshoot the RAM first, followed by the display card and then the motherboard.

Other beeps: Check motherboard manual

Problem: Check the motherboard manual or the vendor’s Web site for more information. Treat it as a motherboard problem.

Solution: Troubleshoot the motherboard.

Award BIOS Award has the least number of documented beep codes. They prefer to display an error message on the screen. Beep codes are used only if the BIOS can’t access the display subsystem.

One long beep: Memory problem

Problem: A problem with the memory or motherboard

Solution: Troubleshoot the memory and the motherboard

One long and two short beeps: Video error

Problem: The BIOS is not able to access the video sub-system

Solution: Troubleshoot the video card, and if the problem persists, go on to the motherboard.

One long and three short beeps: Video error

Problem: The BIOS is not able to access the video sub-system

Solution: Troubleshoot the video card, and the if problem persists, go on to the motherboard.

Continuous beeps: Video / memory problem

Problem: There is a problem with the RAM, display card or motherboard.

Solution: Troubleshoot the RAM first, followed by the display card and then the motherboard.

Other beeps: Check the motherboard manual

Problem: Check the motherboard manual or the vendor’s Web site for more information. Treat it as a motherboard problem.

Solution: Check the motherboard manual. Troubleshoot the motherboard.