2 bios squeaks. Long repeating BIOS beeps - what do they mean? Sound signals Award

Why do you need a BIOS:

1. When the computer boots, it checks for the presence of basic hardware and its functionality. If, for example, RAM, a processor, or another device necessary for PC operation has burned out, the BIOS will give a signal special sound(for each component the set of signals will be different).

2. The BIOS loads the bootloader, which in turn loads the OS.

3. BIOS allows the OS to communicate with peripheral equipment.

4. BIOS allows you to configure many hardware components, monitor their status and operating parameters. The settings made by the user are saved there, for example, the current date and time, and allows you to turn on and off the equipment built into the motherboard.
To determine the BIOS type I recommend looking at the time of boot, usually in the upper left part of the screen there is information about the manufacturer and BIOS version, or going into the BIOS settings, usually pressing the Delete key several times after turning on the PC.

UEFI BIOS

	Description of the error
1 short
2 short	There are non-critical errors.
3 long	The keyboard controller generated an error
1 short + 1 long	RAM is faulty
1 long + 2 short	The video card signals an error
1 long + 3 short	Video memory error
1 long + 9 short	Error reading from ROM
Continuous short beeps	Malfunction of the power supply or RAM
Continuous long beeps	RAM problems
Alternating long and short signals	Processor failure
Continuous signal	Indicates problems with the power supply

Sequence of beeps	Bios error description
1 short	Successful POST
1 beep and blank screen	Video system is faulty
2 short	Monitor not connected
3 long	Motherboard faulty (keyboard controller error)
1 long 1 short	Motherboard is faulty
1 long 2 short	Video system faulty (Mono/CGA)
1 long 3 short	Video system (EGA/VGA) is faulty
Repeating short	Malfunctions related to the power supply or motherboard
Continuous	Problems with the power supply or motherboard
Absent	The power supply, motherboard, or speaker is faulty

Sequence of beeps	Description of the error
1 short	Successful POST
2 short	Minor errors found. A prompt to log in appears on the monitor screen. into the CMOS Setup Utility program and correct the situation. Check the security of the fastening cables in connectors hard drive and motherboard.
3 long	Keyboard controller error
1 short 1 long	Random access memory (RAM) error
1 long 2 short	Video card error
1 long 3 short	Video memory error
1 long 9 short	Error reading from ROM
Repeating short	Problems with the power supply; RAM problems
Repeating long	RAM problems
Repeated high-low frequency	CPU problems
Continuous	Problems with the power supply

Sequence of beeps	Description of the error
1 short	No errors found, PC is working fine
2 short	RAM parity error or you forgot to turn off the scanner or printer
3 short	Error in the first 64 KB of RAM
4 short	System timer malfunction
5 short	Processor problems
6 short	Keyboard controller initialization error
7 short	Problems with the motherboard
8 short	Video card memory error
9 short	BIOS checksum is incorrect
10 short	CMOS write error
11 short	System board cache error
1 long 1 short	Problems with the power supply
1 long 2 short	Video card error (Mono-CGA)
1 long 3 short	Video card error (EGA-VGA)
1 long 4 short	No video card
1 long 8 short	Problems with the video card or the monitor is not connected
3 long	RAM - Read/Write test completed with error. Reinstall the memory or replace it with a working module.
Missing and blank screen	The processor is faulty. The contact leg of the processor may be bent (broken). Check the processor.
Continuous beep	The power supply is faulty or the computer is overheating

AST BIOS

Sequence of beeps	Description of the error
1 short	Error when checking processor registers. Processor failure
2 short	Keyboard controller buffer error. Keyboard controller malfunction.
3 short	Keyboard controller reset error. The keyboard controller or system board is faulty.
4 short	Keyboard communication error.
5 short	Keyboard error.
6 short	System board error.
9 short	Mismatch checksum BIOS ROM. The BIOS ROM chip is faulty.
10 short	System timer error. The system timer chip is faulty.
11 short	Chipset error.
12 short	Power management register error in non-volatile memory.
1 long	DMA controller error 0. The channel 0 DMA controller chip is faulty.
1 long 1 short	DMA controller error 1. The channel 1 DMA controller chip is faulty.
1 long 2 short	Frame retrace suppression error. The video adapter may be faulty.
1 long 3 short	Error in video memory. The memory of the video adapter is faulty.
1 long 4 short	Video adapter error. The video adapter is faulty.
1 long 5 short	Memory error 64K.
1 long 6 short	Failed to load interrupt vectors. BIOS was unable to load interrupt vectors into memory
1 long 7 short	Failed to initialize video hardware.
1 long 8 short	Video memory error.

Phoenix BIOS beeps consist of several series of short beeps that follow at a certain interval. For example, a signal with code 1-2-3 will sound like this: one short beep, pause, two short beeps, pause, three short beeps.

Signal	Meaning (decoding)
	Error when reading data from the built-in CMOS memory chip
	CMOS chip checksum error
	Error on system board
	System board DMA controller error
	Error reading or writing data to one of the DMA channels
	Error in RAM
	Error in the first 64 KB of main memory
	System board error
	RAM testing error
from 2-1-1 to 2-4-4	Error in one of the bits of the first 64 KB of RAM
	Error in the first DMA channel
	Error in the second DMA channel
	Error processing interrupts
	Motherboard interrupt controller error
	Keyboard controller error
	Video adapter error
	Error when testing video memory
	Error while searching for video memory
	System timer error
	Completion of testing
	Keyboard controller error
	Error central processor
	RAM testing error
	System timer error
	Real Time Clock Error
	Serial port error
	Parallel port error
	Math coprocessor error
	Error in the operation of adapters that have their own BIOS
	Error when calculating BIOS checksum
	Error in RAM operation
	Keyboard controller error
	Errors when testing RAM
	Error handling unexpected interrupts

Sequence of sound signals, description of errors without table:

1-1-2 Error during processor test. The processor is faulty. Replace the processor
1-1-3 Error writing/reading data to/from CMOS memory.
1-1-4 An error was detected when calculating the checksum of the BIOS contents.
1-2-1 Motherboard initialization error.
1-2-2 or 1-2-3 DMA controller initialization error.
1-3-1 Error in initializing the RAM regeneration circuit.
1-3-3 or 1-3-4 Error initializing the first 64 KB of RAM.
1-4-1 Motherboard initialization error.
1-4-2 Error initializing RAM.
1-4-3 Error initializing the system timer.
1-4-4 Error writing/reading to/from one of the I/O ports.
2-1-1 An error was detected while reading/writing bit 0 (in hexadecimal) of the first 64 KB of RAM
2-1-2 An error was detected when reading/writing the 1st bit (in hexadecimal) of the first 64 KB of RAM
2-1-3 An error was detected when reading/writing the 2nd bit (in hexadecimal) of the first 64 KB of RAM
2-1-4 An error was detected when reading/writing the 3rd bit (in hexadecimal) of the first 64 KB of RAM
2-2-1 An error was detected when reading/writing the 4th bit (in hexadecimal) of the first 64 KB of RAM
2-2-2 An error was detected when reading/writing the 5th bit (in hexadecimal) of the first 64 KB of RAM
2-2-3 An error was detected when reading/writing the 6th bit (in hexadecimal) of the first 64 KB of RAM
2-2-4 An error was detected when reading/writing the 7th bit (in hexadecimal) of the first 64 KB of RAM
2-3-1 An error was detected when reading/writing the 8th bit (in hexadecimal) of the first 64 KB of RAM
2-3-2 An error was detected when reading/writing the 9th bit (in hexadecimal) of the first 64 KB of RAM
2-3-3 An error was detected when reading/writing the 10th bit (in hexadecimal) of the first 64 KB of RAM
2-3-4 An error was detected when reading/writing the 11th bit (in hexadecimal) of the first 64 KB of RAM
2-4-1 An error was detected while reading/writing the 12th bit (in hexadecimal) of the first 64 KB of RAM
2-4-2 An error was detected when reading/writing the 13th bit (in hexadecimal) of the first 64 KB of RAM
2-4-3 An error was detected when reading/writing the 14th bit (in hexadecimal) of the first 64 KB of RAM
2-4-4 An error was detected when reading/writing the 15th bit (in hexadecimal) of the first 64 KB of RAM
3-1-1 Error initializing the second DMA channel.
3-1-2 or 3-1-4 Error initializing the first DMA channel.
3-2-4 Keyboard controller initialization error.
3-3-4 Error initializing video memory.
3-4-1 Serious problems occurred when trying to access the monitor.
3-4-2 The video card BIOS cannot be initialized.
4-2-1 System timer initialization error.
4-2-2 Testing completed.
4-2-3 Keyboard controller initialization error.
4-2-4 Critical error when the central processor enters protected mode.
4-3-1 Error initializing RAM.
4-3-2 Error initializing the first timer.
4-3-3 Error in initializing the second timer.
4-4-1 Error initializing one of the serial ports.
4-4-2 Parallel port initialization error.
4-4-3 Math coprocessor initialization error.
Long, continuous beeps—the motherboard is faulty.
The sound of a siren from high to low frequency means the video card is faulty, check the electrolytic capacitors for leaks or replace everything with new ones that are known to be good.
Continuous signal - the CPU cooler is not connected (faulty).

In contact with

In this article we have collected the most common BIOS signals for diagnosing computer malfunctions. But, if your computer is making a beep that is not listed below, please refer to the guide to identify the faulty hardware components.

The POST (power-on self-test) feature checks your computer's internal hardware to ensure compatibility and connectivity before booting. If your computer boots normally, it may beep once (some computers may beep twice) as it starts up and continues to boot. However, if the computer crashes, it will either not beep or beep, which indicates a problem.

Content:

AMI BIOS beeps

Below are the AMI BIOS beeps. However, due to the wide variety of different computer manufacturers running this BIOS, the beep codes may vary.

Sound signal	Description
1 short
2 short	Parity circuit failure
3 short	Base 64 K RAM failure
4 short	System timer failure
5 short	Process failure
6 short	Keyboard controller Gate A20 error
7 short	Virtual mode exception error
8 short	Display memory Read/Write test failure
9 short	ROM BIOS checksum failure
10 short	CMOS shutdown Read/Write error
11 short	Cache Memory error
1 long, 3 short	Conventional/Extended memory failure
1 long, 8 short	Display/Retrace test failed
Two tone siren

AWARD BIOS beeps

Below are the Award BIOS beep codes. Also, due to the wide variety of different computer manufacturers with this BIOS, the sound codes may differ.

Sound signal	Description
1 long, 2 short	Indicates a video error has occurred and the BIOS cannot initialize the video screen to display any additional information. (Video adapter not detected or video memory error)
1 long, 3 short	Video card not detected (reseat video card) or bad video card (Depending on the BIOS version, this signal may indicate a video adapter error or a keyboard error)
Endless repeating beep	RAM problem. (RAM problems)
Repeated high-frequency beeps while PC is running	Overheating processor (CPU)
Repeated beeps alternate between high and low frequencies	Issue with the processor (CPU), possibly damaged.

If any other hardware problems are detected, the BIOS will display a message.

Dell beeps

For other Dell signals, you can refer to the page.

IBM BIOS beeps

Below are the IBM BIOS beep codes.

Sound signal	Description
Absent	No Power, Loose Card, or Short. (The power supply, motherboard, or speaker is faulty)
1 short	Normal POST, computer is ok. (No errors found)
2 short	POST error, review screen for error code.
Continuous beep
Repeat short beep	No Power, Loose Card, or Short. (No power supply)
1 long 1 short	Motherboard issue. (Problem with motherboard)
1 long and 2 short	Video (Mono/CGA Display Circuitry) issue.
1 long 3 short.	Video (EGA) Display Circuitry.
3 long	Keyboard or Keyboard card error. (Keyboard problems)
1 Beep and black screen	Video Display Circuitry. (Faulty monitor)

Phoenix BIOS beeps

Below are the beep codes for Phoenix BIOS Q3.07 ​​OR 4.X

Sound signal	Description
1-1-1-1	Unconfirmed beep code. Reseat RAM chips or replace RAM chips as possible solution
1-1-1-3	Verify Real Mode. (Check Real Mode).
1-1-2-1	Get CPU Type. (Select processor type)
1-1-2-3	Initialize system hardware. (Initialize system hardware)
1-1-3-1	Initialize chipset registers with initial POST values. (Initialize the chipset register with POST initial values).
1-1-3-2	Set in POST flag. (Enable POST).
1-1-3-3	Initialize CPU registers. (Initialize the processor register).
1-1-4-1	Initialize cache to initial POST values.
1-1-4-3	Initialize I/O. (Initialize I/O).
1-2-1-1	Initialize Power Management. (Initialize power management).
1-2-1-2	Load alternate registers with initial POST values.
1-2-1-3	Jump to UserPatch0.
1-2-2-1	Initialize keyboard controller. (Initialize the keyboard controller).
1-2-2-3	BIOS ROM checksum. (BIOS ROM checksum).
1-2-3-1	8254 timer initialization. (8254 initialize timer)
1-2-3-3	8237 DMA controller initialization. (8237 initialize DMA controller).
1-2-4-1	Reset Programmable Interrupt Controller. (Reset the software interrupt controller).
1-3-1-1	Test DRAM refresh. (Check DRAM update).
1-3-1-3	Test 8742 Keyboard Controller. (8742 keyboard controller).
1-3-2-1	Set ES segment to register to 4 GB. (Set ES segment for registration to 4 GB).
1-3-3-1	28 Autosize DRAM. (28 Autosize DRAM).
1-3-3-3	Clear 512K base RAM.
1-3-4-1	Test 512 base address lines.
1-3-4-3	Test 512K base memory
1-4-1-3	Test CPU bus-clock frequency. (Check the CPU bus frequency.)
1-4-2-4	Reinitialize the chipset. (Re-initialize the chipset).
1-4-3-1	Shadow system BIOS ROM. ( Test system BIOS ROM).
1-4-3-2	Reinitialize the cache. (Reinitialize cache).
1-4-3-3	Autosize cache.
1-4-4-1	Configure advanced chipset registers.
1-4-4-2	Load alternate registers with CMOS values. (Loading alternate registers with CMOS values).
2-1-1-1	Set Initial CPU speed. (Set the initial processor speed)
2-1-1-3	Initialize interrupt vectors. (Initialize interrupt vectors).
2-1-2-1	Initialize BIOS interrupts. (Initialize BIOS interrupts).
2-1-2-3	Check ROM Copyright notice.
2-1-2-4	Initialize manager for PCI Options ROMs.
2-1-3-1	Check video configuration against CMOS. (Check the CMOS video configuration).
2-1-3-2	Initialize PCI bus and devices. (Initialize PCI and device bus).
2-1-3-3	Initialize all video adapters in system. (Initialize all video adapters in the system).
2-1-4-1	Shadow video BIOS ROM.
2-1-4-3	Display Copyright notice. (Copyright Notice).
2-2-1-1	Display CPU Type and speed. (Display processor type and speed).
2-2-1-3	Test keyboard. (Keyboard test).
2-2-2-1	Set key click if enabled. (Install the key if enabled).
2-2-2-3	56 Enable keyboard. (56 Turn on the keyboard).
2-2-3-1	Test for unexpected interrupts. (Check for unexpected interruptions).
2-2-3-3	Display prompt Press F2 to enter SETUP. (Prompt display Press F2 to enter SETUP.)
2-2-4-1	Test RAM between 512 and 640 k. (Check RAM between 512 and 640 k).
2-3-1-1	Test expanded memory. (Check memory expansion).
2-3-1-3	Test extended memory address lines. (Test extended memory address lines).
2-3-2-1	Jump to UserPatch1. (Jump to UserPatch1).
2-3-2-3	Configure advanced cache registers. (Configure extended cache registers).
2-3-3-1	Enable external and CPU caches. (Enable CPU cache).
2-3-3-3	Display external cache size. (Display external cache size).
2-3-4-1	Display shadow message. (Display shadow message).
2-3-4-3	Display non-disposable segments.
2-4-1-1	Display error messages.
2-4-1-3	Check for configuration errors. (Check for configuration errors).
2-4-2-1	Test real-time clock. (Check that the time is correct).
2-4-2-3	Check for keyboard errors.
2-4-4-1	Set up hardware interrupts vectors. (Configure hardware vector interrupts).
2-4-4-3	Test coprocessor if present. (Check the coprocessor if there is one).
3-1-1-1	Disable onboard I/O ports. (Disabled I/O ports).
3-1-1-3	Detect and install external RS232 ports.
3-1-2-1	Detect and install external parallel ports. (Detecting and installing external parallel ports).
3-1-2-3	Re-initialize onboard I/O ports. (Reinitialize the I/O ports).
3-1-3-1	Initialize BIOS Data Area. (Initialize BIOS data areas).
3-1-3-3	Initialize Extended BIOS Data Area. (Initialize BIOS data areas).
3-1-4-1	Initialize floppy controller. (Initialize the floppy disk controller).
3-2-1-1	Initialize hard disk controller. (Initialize the hard disk controller).
3-2-1-2	Initialize local bus hard disk controller. (Initialize local bus hard disk controller).
3-2-1-3	Jump to UserPatch2
3-2-2-1	Disable A20 address line. (Disable the A20 address bar).
3-2-2-3	Clear huge ES segment register.
3-2-3-1	Search for option ROMs.
3-2-3-3	Shadow option ROMs.
3-2-4-1	Set up Power Management. (Set up power management).
3-2-4-3	Enable hardware interrupts. (Enable hardware interrupts).
3-3-1-1	Set time of day. (Set time).
3-3-1-3	Check key lock. (Check the keypad lock).
3-3-3-1	Erase F2 prompt.
3-3-3-3	Scan for F2 key stroke.
3-3-4-1	Enter SETUP.
3-3-4-3	Clear in POST flag.
3-4-1-1	Erase F2 prompt. (Check for errors).
3-4-1-3	POST done, prepare to boot operating system.
3-4-2-3	Check password (optional). (Check your password).
3-4-3-1	Clear global descriptor table.
3-4-4-1	Clear parity checkers.
3-4-4-3	Clear screen (optional).
3-4-4-4	Check virus and backup reminders.
4-1-1-1	Try to boot with INT 19.
4-2-1-1	Interrupt handler error. (Interrupt handler error).
4-2-1-3	Unknown interrupt error. (Unknown interrupt error).
4-2-2-1	Pending interrupt error. (Pending interrupt error).
4-2-2-3	Initialize option ROM error.
4-2-3-1	Shutdown error. (Shutdown error).
4-2-3-3	Extended Block Move.
4-2-4-1	Shutdown 10 error.
4-3-1-3	Initialize the chipset. (Initialize chipset).
4-3-1-4	Initialize refresh counter. (Initialize update counter).
4-3-2-1	Check for Forced Flash.
4-3-2-2	Check HW status of ROM.
4-3-2-3	BIOS ROM is OK.
4-3-2-4	Do a complete RAM test. (Do a full RAM check).
4-3-3-1	Do OEM initialization.
4-3-3-2	Initialize interrupt controller. (Initialize interrupt controller).
4-3-3-3	Read in bootstrap code.
4-3-3-4	Initialize all vectors.
4-3-4-1	Boot the Flash program.
4-3-4-2	Initialize the boot device.
4-3-4-3	Boot code was read OK.
Two tone siren	Low CPU Fan speed, Voltage Level issue ( Low frequency CPU fan rotation, voltage level problem).

Reset BIOS to default settings

The easiest way to reset your computer's BIOS settings is through its menu. To open the menu, restart your computer and press the key that appears on the boot screen, in most cases this is Delete or F2.

In the BIOS, find the parameter ( Reset to default, Load factory defaults, Clear BIOS settings, Load setup defaults), or something similar. Select it using the arrow keys, press Enter and confirm the operation. The BIOS will now use its default settings.

Another way to reset the settings is to remove the battery that is located on the motherboard computer.

First, make sure your computer is turned off. Locate the round, flat battery on the motherboard and carefully remove it. Wait five minutes before replacing it. The settings will also be reset to factory settings.

Installation of new equipment

Compared to other BIOS manufacturers' beep sounds, BIOS AMI beep sounds are more varied. In most cases, these beeps allow you to identify a malfunction during the computer boot stage and the POST hardware test procedure. Typically, all you need to do to determine which component is causing the problem is to count the number of beeps emitted by the system speaker.

Below are the beeps produced by the BIOS AMI. In all cases, the number of signals and their type (long/short) are indicated.

• No signals

This situation is perhaps the most unpleasant that a user can encounter. As a rule, it means that power is not supplied to the motherboard or the BIOS is generally faulty. No power to the motherboard usually means either a faulty/broken power cable or a faulty computer power supply.

• One short

A single short signal is the same signal that all users are accustomed to hearing every time they start their PC. It means that no errors or problems were detected during the hardware check, and the computer can continue to boot.

• Long continuous

This signal means that the PC power supply is faulty. However, unlike the situation with a complete absence of signals, in this case power is supplied to the motherboard, but its parameters do not correspond to the nominal value.

• Two short

This signal indicates an error in the RAM. This error may indicate either a malfunction of the memory modules themselves, or simply that one of the modules is poorly inserted into the slot.

• Three short

This type of signal also indicates an error in the RAM. But this error is quite specific and rarely encountered - it is an error in the first 64 KB of RAM.

• Four short

This signal indicates a system timer malfunction. Fortunately, this type of malfunction occurs infrequently, but it is not uncommon the only way The solution is to replace the entire motherboard.

• Five short

In a similar way, the BIOS informs the user about a malfunction of the heart of the personal computer - the central processor. However, this malfunction may not always be associated with a defect in the processor chip itself. Often, to fix the problem, it is enough to check that the processor is securely installed in the socket.

• Six short

This message indicates that the keyboard controller is faulty or that the keyboard itself is missing. Very often, to correct this situation, it is enough to check the contact in the keyboard connector on the system unit.

• Seven short

Such a set of sounds indicates a rather serious malfunction - namely, a failure of the system board. However, sometimes the error may disappear after checking the power cable contacts on the motherboard.

• Eight short

BIOS message indicating video memory failure. But here, as with many other errors, sometimes the problem may simply be poor contact - in this case, between the motherboard slot and the video card.

• Nine short

In this case, the BIOS signals a BIOS memory checksum error. The reasons for this phenomenon can be different - an error in the new BIOS version or a random failure in the CMOS memory. Often the problem can be fixed by flashing the BIOS.

• Ten short

With this set of signals, the BIOS reports an error in writing to CMOS memory. As a rule, this error is more serious than the previous one and often requires the intervention of a specialist from a service workshop.

• Eleven short

• One long, then two, three or eight short

This type of informational message tells the user that there are video card errors. Typically, such sound signals are only generated when using old video cards (Mono/CGA/EGA), so the chance of encountering them is currently extremely small. In most cases, this malfunction can be eliminated by carefully installing the video card in the connector.

It is quite familiar to many users to hear a beep from system unit when you turn on the computer's power. A single short signal indicates that “everything is in order.” And if, for example, 1 long signal or a series of sounds sounds instead, then it immediately becomes clear that a problem has occurred. This emits signals from the BIOS, the very program that runs first and tests all the components of the computer (from the central processor to the monitor).

The BIOS emits signals during the initial testing of the components of the system unit, while the video card has not yet been initialized, which can display certain text and tabular data on the monitor. Using them, you can identify a faulty unit inside the system unit or identify poor contact of external connections.

BIOS errors are coded into a specific combination of long and short signals. Moreover, they are all the same for motherboards of different years of production from almost all manufacturers (from the most famous to “noname”). BIOS error codes have audio detailed description in the instructions for the motherboard, however, often in English.

The BIOS can produce sounds under one obligatory condition: a small system speaker, as it is called, must be connected to the motherboard. Otherwise, BIOS errors will go unnoticed and the user will only see dark screen monitor.

Sound signals: what is needed to decipher them?

If a single BIOS signal indicates normal startup of the computer, then a series of the same short or long sounds (combinations thereof) indicates the detection of problems, moreover, of a hardware nature. Then you will have to open the cover of the system unit. And even if the user does not interfere with the PC device himself, for example, due to the presence of factory seals on the cover screws, decoding these signals will help determine the source of the problem.

The beep sounds may be different for different computer manufacturers because they use different BIOS versions. However, among them you can find those that are typical and most frequently used.

Diagnostics using BIOS sound signals is one of the most effective methods, without the use of special test boards (such as POST-card), therefore, despite the systematic development of production technologies, all motherboards come with a small speaker or at least a connector for connecting it.

Sound signals are produced if there is a working power supply and speaker. If they are faulty, then no diagnosis will be possible. A faulty speaker can only be determined by replacing it with a known good one, which is not always available.

When everything works as intended, in order to decipher the error codes, you should use a special list that indicates typical signals for a given BIOS version.

Award BIOS beep codes

The most common among the numerous BIOS versions are considered to be those from the developer Award, which has been making its own programs for motherboards since the times when the Pentium brand did not even exist.

The list of typical signals that are the same for all versions of Award BIOS is as follows:

1. Continuous signal. Damage to the power supply. The easiest way to check whether this is true is by replacing the power supply with a known good one.
2. 2 short. The BIOS pays attention to minor errors, which, however, require entering the correct parameters, for example, by loading standard factory settings.
3. 3 long. The problem is with the keyboard block on the motherboard. The cause may be a short circuit in the keyboard or connecting cable, or in the motherboard (connector, electronics, electrically conductive dust, etc.).
4. 1 long, 1 short. BIOS errors are caused by RAM modules. The easiest way to fix the problem is to remove the modules, blow the accumulated dust out of the connector, clean the contacts on the modules themselves and insert them back into the connector. You can leave only one module for the test period and, if necessary, change them, determining which one causes sound signals.
5. 1 long, 2 short. . For some video card models, such codes are issued when there is poor contact in the monitor connector, when at the moment of turning on the BIOS cannot detect the presence of a connection with it. To fix the problem, you can do the same with the video card as with the RAM in the previous paragraph.
6. 1 long, 3 short. The BIOS was unable to initialize the keyboard, which may indicate a problem with the keyboard itself or the connector or electronics of the motherboard. The easiest way is to temporarily disable the keyboard, then it will immediately become clear whether it is the source of the problem.
7. 1 long, 9 short. The BIOS chip itself is faulty. You just need to turn off your computer for a while and try to turn it on again. If the situation persists and the BIOS error codes do not change, then you should replace the motherboard or try to flash the chip using a special programmer.
8. 1 long, constantly repeating. Error while initializing memory. It is necessary to replace the modules or, at least, clean the contacts in the connector and try to turn on again.
9. 1 short, constantly repeated. Incorrect operation of the power supply. In any case, only replacing it with a working unit or repairing the existing unit will help. Bad contacts are practically never found here due to the large connectors compared to other components of the system unit.

AMI BIOS beep codes

The AMI developer is found less often in the BIOS of motherboards than its competitor Award, but, nevertheless, it has firmly occupied its own, albeit small, niche in this market, so you must be prepared to encounter its audio signal encoding system.

Decoding the coding of audio signals:

1. 2 short. The error is caused by incorrect operation of the RAM. In any case, you need to start by cleaning the connectors from dust, even if you plan to immediately install new modules to replace the “suspicious” ones.
2. 3 short. Like the previous point, this indicates a faulty RAM module.
3. 4 short. The system timer, which is the basis for the operation of all other components of the motherboard, is faulty. The only thing that can be done without replacing it is to turn off the system unit for a while.
4. 5 short. Error while initializing the CPU. You can either turn off the system unit for a while or remove the cooling system from the processor, pull it out of the connector, and then insert it back. If all else fails, then you will have to change the processor.
5. 6 short. The keyboard or its processing unit on the motherboard is faulty. To clarify the source, you can temporarily disable the keyboard and replace it with a known-good copy.
6. 7 short. There is a problem with the motherboard. In such a situation, a careful external inspection of the board for the presence of debris closing the contacts can help.
7. 8 short. The video card is faulty. You should replace it or, as a last resort, clean the contacts in the connector. You can temporarily turn on the built-in video card and check the computer's operation with it (if, of course, it is available).
8. 1 long, 2 short. Error while initializing the video card. The solutions are the same as in the previous paragraph.
9. 1 long, 3 short. There is a problem with the video card.
10. 1 long, 8 short. There is a problem with either the video card or the monitor.

The following lists of BIOS signals are the basis for diagnosing a computer when there are no other options. In most cases, they allow you to determine the source of the problem, which can simply be replaced with a known-good unit.

American Megatrends, Inc. (AMI)

The checkpoints of the POST procedures performed in AMIBIOS were redesigned and supplemented in 1995 and have not undergone significant changes to date. The first description of POST codes or, as AMI calls them, “check points” in their current form appeared in connection with the release of the V6.24 kernel, 07/15/95. Some changes have been made to AMIBIOS V7.0, which are reflected in this document.

Features of performing AMIBIOS startup procedures

If during the startup process the data 55h, AAh appears in the diagnostic port, you should not compare this information with POST codes - we are dealing with a typical test sequence, the task of which is to check the integrity of the data bus.

At the start stage, the output to the diagnostic port of data is specific to each platform. In some implementations, the first code rendered is associated with actions, which AMI calls chipset specific stuff. This procedure is accompanied by outputting the CCh value to port 80h and performing a number of actions to configure the system logic registers. As a rule, the CCh code appears in cases where system logic from Intel is used, built on the basis of the PIIX controller - these are TX, LX, BX chipsets.

Some on-board I/O chips contain an RTC and a keyboard controller, which are disabled at startup. The purpose of the BIOS is to initialize these board resources for further use. In this case, the first startup procedure associated with setting up the keyboard controller is accompanied by the output of the value 10h, then the RTC is initialized, as evidenced by the appearance of the DDh code in the diagnostic port. It should be noted that the failure of at least one of these resources will result in the system board as a whole not starting at the very first stage of POST execution.

On a number of boards, the initialization process begins with the CPU switching to protected mode. In this case, following the first rendered code 43h, the POST execution continues as described in the AMIBIOS documentation - control is transferred to point D0h.

Unpacked initialization procedure codes

Uncompressed Init Code Check Points

Error code	Description of the error
E.E.	In modern AMIBIOS implementations, the first code rendered is associated with accessing the device from which it is possible to boot to restore the BIOS
CC	Initializing system logic registers CD Flash ROM type not recognized
C.E.	Checksum mismatch in the starting BIOS CF Error in accessing the spare Flash ROM chip
DD	Early initialization of the RTC, which is integrated into the SIO chip
D0	Disable non-maskable NMI interrupt. Testing the time delay for attenuation of transient processes. Checking the Boot Block checksum, stopping if there is a mismatch
D1	Perform memory regeneration procedure and Basic Assurance Test. Switching to 4 GB memory addressing mode
D3	Determination of capacity and primary memory test
D4	Return to real memory addressing mode. Early initialization of the chip set. Stack Installation
D5	Transferring the POST module from Flash ROM to the transit memory area
D6	If the checksum does not match or CTRL+Home, a transition to the procedure is performed Flash recovery ROM (Code E0)
D7	Transfer of control utility program, which unpacks the system BIOS
D8	Full unboxing system BIOS
D9	Transferring system BIOS control to Shadow RAM
D.A.	Reading information from SPD (Serial Presence Detect) DIMM DB modules Setting MTRR of CPU registers
DC	The memory controller is programmed according to data received from SPD DE System memory configuration error. Fatal error
DF	System memory configuration error. Beep 10 Early
11	Return from STR (Suspend to RAM) state
12	Restoring access to SMRAM (System Management RAM)
13	Memory regeneration restoration
14	Finding and initializing VGA BIOS

Flash ROM rewrite procedure codes

Boot Block Recovery Codes

Error code	Description of the error
E0	Preparations are being made to intercept INT19 and the ability to start the system in simplified mode is checked.
E1	Setting interrupt vectors
E3	Recovering CMOS contents, searching and initializing BIOS
E2	Preparing interrupt controllers and direct memory access
E6	Enable system timer and FDC interrupts
E.C.	Reinitializing IRQ and DMA ED controllers Initializing the disk drive
E.E.	Reading boot sector from EF floppy Disk operation error
F0	Finding the AMIBOOT.ROM file
F1	The file AMIBOOT.ROM was not found in the root directory F2 Read FAT
F3	Reading AMIBOOT.ROM
F4	The size of the AMIBOOT.ROM file does not match the size of the Flash ROM
F5	Disabling Internal Cache
FB	Flash ROM Type Definition
F.C.	Erasing the main Flash ROM block
FD	Programming the main Flash ROM block
FF	Restart BIOS

Unpacked system BIOS codes executed in ShadowRAM

Runtime code is uncompressed in F000 shadow RAM

Error code	Description of the error
03	Disable non-maskable NMI interrupt. Reset Type Definition
05	Stack initialization. Disable memory caching and USB controller
06	Executing a utility program in RAM
07	Processor recognition and APIC initialization
08	Checking the CMOS checksum
09	Checking the operation of the End/Ins keys
0A	Battery failure check
0B	Clearing the keyboard controller buffer registers
0C	A test command is sent to the keyboard controller
0E	Search additional devices served by the keyboard controller
0F	Initializing the keyboard
10	A reset command is sent to the keyboard
11	If the End or Ins key is pressed, the CMOS 12 is reset. Placing the DMA controllers in a passive state.
13	Chipset initialization and L2 cache
14	Checking the system timer
19	DRAM regeneration request generation test is running
1A	Checking the duration of the regeneration cycle
20	Initializing Output Devices
23	The keyboard controller input port is read. Keylock Switch and Manufacture Test Switch are interrogated
24	Preparing to initialize the interrupt vector table
25	Interrupt vector initialization complete
26	The status of the Turbo Switch jumper is polled through the keyboard controller input port
27	Primary initialization of the USB controller. Updating the microcode of the starting processor
28	Preparing to install video mode
29	Initializing the LCD panel
2A	Search for devices supported by additional ROMs
2B	Initializing VGA BIOS, checking its checksum
2C	Executing VGA BIOS
2D	Matching INT 10h and INT 42h
2E	Search for CGA video adapters
2F	CGA adapter video memory test
30	Test of CGA adapter scan generation circuits
31	Error in video memory or scanning circuits. Finding an alternative CGA video adapter
32	Test of video memory of an alternative CGA video adapter and scan circuits
33	Poll the status of the Mono/Color jumper
34	Setting text mode 80x25
37	Video mode is set. Screen cleared
38	Initialization of on-board devices
39	Displaying error messages from the previous step
3A	Displaying the “Hit DEL” message to enter CMOS Setup
3B	Start preparing for a memory test in protected mode
40	Preparing GDT and IDT descriptor tables
42	Switching to protected mode
43	The processor is in protected mode. Interrupts enabled
44	Preparing to test the A20 line
45	A20 line test
46	RAM size determination completed
47	Test data recorded in Conventional Memory
48	Rechecking Conventional Memory
49	Extended Memory Test
4B	Memory reset
4C	Indication of the zeroing process
4D	Recording in CMOS the resulting sizes Conventional and Extended memory 4E Indication of the actual amount of system memory
4F	Extended Conventional Memory test running
50	Conventional Memory size correction
51	Extended Memory test
52	Conventional Memory and Extended Memory volumes saved
53	Delayed parity error handling
54	Disable parity and non-maskable interrupt processing
57	Initializing the memory region for POST Memory Manager
58	You are prompted to enter CMOS Setup
59	Returning the processor to real mode
60	Checking page DMA registers
62	Test of address registers and forwarding length of DMA#1 controller
63	Test of address registers and forwarding length of DMA#2 controller
65	Programming DMA controllers
66	Clearing the Write Request and Mask Set POST registers
67	Programming Interrupt Controllers
7F	Resolving NMI request from additional sources
80	Sets the interrupt servicing mode from the PS/2 port
81	Keyboard interface test for reset errors
82	Setting the keyboard controller operating mode
83	Checking Keylock Status
84	Memory capacity verification
85	Displaying Error Messages
86	Configuring the system for Setup operation
87	Unpacking the CMOS Setup program into Conventional Memory.
88	Setup program completed by user
89	Completed state recovery after Setup operation
8B	Reserving memory for an additional BIOS variable block
8C	Programming Configuration Registers
8D	Primary initialization of HDD and FDD controllers
8F	Reinitializing the FDD Controller
91	Controller configuration hard drives
95	Performing a ROM Scan to look for additional BIOSes
96	Additional configuration of system resources
97	Verifying the signature and checksum of the optional BIOS
98	Setting up System Management RAM
99	Setting the timer counter and parallel port variables 9A Generating a list of serial ports
9B	Preparing an area in memory for a coprocessor test
9C	Initializing the coprocessor
9D	Coprocessor information is stored in CMOS RAM
9E	Keyboard Type Identification
9F	Search for additional input devices
A0	Formation of MTRR registers (Memory Type Range Registers)
A2	Error messages from previous initialization steps
A3	Setting the keyboard auto-repeat timing
A4	Defragmenting unused RAM regions
A5	Setting the video mode
A6	Cleaning the screen
A7	Transferring BIOS executable code to Shadow RAM area
A8	Initializing additional BIOS in segment E000h
A9	Returning control to the system BIOS AA Initializing the USB bus
AB	Preparing the INT13 module to serve disk services
A.C.	Building AIOPIC tables to support multiprocessor AD systems Preparing the INT10 module to serve video services
A.E.	DMI initialization
B0	System Configuration Table Output B1 ACPI BIOS Initialization
00	Software interrupt INT19h – Boot Sector loading

Features of the Device Initialization Manager

In addition to the above POST codes, messages about events during the execution of Device Initialization Manager (DIM) are output to the diagnostic port. There are several control points that indicate the initialization status of system or local buses.

The information is displayed in word format, the low byte of which coincides with the system POST code, and the high byte indicates the type of initialization procedure being performed. The most significant tetrad in the high byte indicates the type of procedure being executed, and the low tetrad determines the bus topology for its application.

Senior tetrad

Junior tetrad

If a system memory configuration error is detected, the DE code, DF code, and configuration error code are output to port 80h sequentially in an endless loop, which can take the following values:

2. Award BIOS V4.51PG Elite

AwardBIOS V4.51PG Elite

The dynamically developing company Award Software in 1995 proposed a new solution in the field of low-level software- AwardBIOS "Elite", better known as V4.50PG. The control point maintenance mode has not changed either in the widespread version V4.51 or in the rare version V4.60. The suffixes P and G denote support for the PnP mechanism and support for energy saving functions (Green Function), respectively.

Performing a POST in Shadow RAM

Error code	Description of the error
03	Disable NMI, PIE (Periodic Interrupt Enable), AIE (Alarm Interrupt Enable), UIE (Update Interrupt Enable). Prohibition of generation of programmable frequency SQWV
04	Checking the generation of requests for DRAM regeneration
05
06	Test the memory area starting at address F000h, where BIOS 07 is located Checking the functioning of CMOS and battery power
BE	Programming the configuration registers of the South and North Bridges
09	Initializing the L2 Cache and Advanced Cache Control Registers on the Cyrix Processor
0A	Generating a table of interrupt vectors. Configuring Power Management Resources and Setting the SMI Vector
0B	Checking the CMOS checksum. Scanning PCI bus devices. Processor microcode update
0C	Initializing the Keyboard Controller
0D	Finding and initializing the video adapter. Setting up IOAPIC. Clock measurements, FSB setting
0E	MPC initialization. Video memory test. Displaying the Award Logo
0F	Checking the first DMA 8237 controller. Keyboard detection and internal test. BIOS checksum verification
10	Checking the second DMA 8237 controller
11	Checking DMA controller page registers
14	Test of system timer channel 2 15 Test of the request masking register of the 1st interrupt controller
16	Test of the request masking register of the 2nd interrupt controller 19 Checking the passivity of the NMI non-maskable interrupt request
30	Determination of the volume of Base Memory and Extended Memory. APIC setup. Software control Write Allocation mode

Error code	Description of the error
31	The main on-screen RAM test. USB initialization
32	The Plug and Play BIOS Extension splash screen appears. Setting up Super I/O resources. Programmable Onboard Audio Device
39	Programming the clock generator via the I2C bus
3C	Setting the software flag to allow entry into Setup
3D	Initializing PS/2 mouse
3E	Initializing the External Cache controller and enabling Cache BF Setting up the chipset configuration registers
41	Initializing the floppy disk subsystem
42	Disable IRQ12 if PS/2 mouse is missing. The hard drive controller is being soft reset. Scanning other IDE devices
43
45	Initializing the FPU coprocessor
4E	Display of error messages
4F	Password Request
50	Restoring a previously stored CMOS state in RAM
51	Resolution of 32 bit access to HDD. Configuring ISA/PnP Resources
52	Initializing additional BIOS. Setting the values ​​of PIIX configuration registers. Formation of NMI and SMI
53
60	Installing BOOT Sector antivirus protection
61	Final steps to initialize the chip set
62	Reading the keyboard ID. Setting its parameters
63	Correction of ESCD, DMI blocks. Clearing RAM
FF	Transferring control to the bootloader. BIOS executes INT 19h command

3. Award BIOS V6.0 Medallion

AwardBIOS V6.0 Medallion

The first mention of Award Medallion BIOS, Version 6.0 dates back to May 12, 1999. The structure of the new product remained unchanged, retaining the early (Early), late (Late) and final (System) initialization phases hardware. Significant changes affected the POST execution algorithms, which was reflected in the new encoding of checkpoints, significantly expanding their scope of application. However, in the new BIOS there was no place for outdated technologies such as EISA, and for this reason a number of POST codes were abolished.

Executing startup POST procedures from ROM

At the early initialization stage, the BIOS program code is executed from the Boot Block in the Flash ROM, and is accompanied by the output of checkpoints 91h...FFh to the diagnostic port

Error code	Description of the error
91	Selecting a startup script for the CF platform Determining the processor type
C0	External Cache prohibition. Internal Cache prohibition. Ban Shadow RAM. Programming the DMA controller, interrupt controller, timer, RTC C1 block Determining the memory type, total volume and placement on 0C lines Checking checksums
C3	Checking the first 256K DRAM for the Temporary Area organization. Unpacking BIOS in Temporary Area
C5	If the checksums match, the POST code being executed is transferred to Shadow. Otherwise, control is transferred to the BIOS recovery procedure
B0	Initializing North Bridge
A0-AF	Hardware-dependent system logic initialization procedure E0-EF Error during system logic initialization process

BIOS recovery

Performing a POST in Shadow RAM

Late initialization is performed in RAM and continues until the user menu is called - CMOS Setup. This POST phase is characterized by the use of memory segment E000h, in which the passage of checkpoints from 01h to 7Fh is processed.

Error code	Description of the error
01	Unpacking XGROUP at physical address 1000:0000h
03	Early
05	Setting the initial values ​​of variables that specify image attributes. Checking the CMOS Status Flag
07	Checking and initializing the keyboard controller
08	Determining the interface type of the connected keyboard
0A	Procedure for autodetection of keyboard and mouse. Final settings of the keyboard controller using PCI space registers
0E	Testing memory segment F000h
10	Type definitions installed memory FlashROM
12	CMOS test
14	Chipset register initialization procedure
16	Primary initialization of the on-board frequency synthesizer
18	Definitions of the installed processor and the size of its Cache L1 and L2 1B Generation of the interrupt vector table
1C
1D	Initial setup of the Power Management system
1F	Loading the keyboard matrix from the XGROUP external module
21	Initializing the Hardware Power Management subsystem
23	Coprocessor testing. Determining the FDD drive type. Preparatory stage for creating a resource map of PnP devices
24	Processor microcode update procedure. Resource distribution map update
25	Initialization and scanning of the PCI bus
26	Configuring the logic that serves the VID (Voltage Identification Device) lines. Initialization of the on-board voltage and temperature monitoring system
27	Reinitializing the Keyboard Controller
29	Initialization of the APIC included in the central processor. Measuring the frequency at which the processor operates. Setting up system logic registers. Initializing the IDE Controller
2A
2B	Search VGA BIOS
2D	Displaying processor information
33	Performing a Reset on a connected keyboard
35	Checking the first channel of the 8237 DMA controller
37	Checking the second channel of the DMA 8237 controller
39	Testing DMA page registers
3C	Setting up the Programmable Interval Timer (8254) controller
3E	Initializing the 8259 Master Controller
40	Initialization of Slave controller 8259
43	Preparing the interrupt controller for operation. Interrupts are disabled, they are enabled later, after a memory test
45	Checking the Passivity of a Non-Maskable Interrupt (NMI) Request
47	Performing ISA/EISA tests
49	Determining the amount of basic and extended memory. Software control of Writes Allocation mode by adjusting AMD K5 registers
4E	Testing memory within the first megabyte and visualizing the results on the display screen. Initializing caching schemes for single and multiprocessor systems, setting up Cyrix M1 processor registers
50	USB initialization
52	Testing of all available system memory, including the region for the built-in video controller (Shared Memory). Visualization of results on the display screen
53	Resetting your login password
55	Visualization of the number of detected processors
57	Initial initialization of ISA PnP devices, each of which is assigned a CSN (Card Select Number). Rendering of the EPA logo
59	Initializing the anti-virus support system
5B	Start of the procedure BIOS updates from a 5D floppy drive Initializing on-board SIO and Audio controllers
60	Access to CMOS Setup is open
63	Initializing PS/2 Mouse
65	Initializing USB Mouse
67	Use of IRQ12 by PCI devices if there is no PS/2 Mouse in the system 69 Full initialization of the L2 cache controller
6B	Chipset initialization according to CMOS Setup
6D	Configuring Resources for ISA PnP Devices in SIO 6F Configuration Mode Initializing the Floppy Disk Subsystem
73	Preliminary steps to initialize the hard drive subsystem. On some platforms - poll ALT+F2 to launch AwardFlash
75	Finding and initializing IDE devices
77	Initializing serial and parallel ports
7A	Software reset of the coprocessor, writing the control word to the FPU register CW 7C Installing protection against unauthorized writing to hard drives
7F	Display error messages. Maintaining the DEL and F1 keys

Preparing tables, arrays and structures for starting the operating system

Starting with code 82h, POST configures the system according to the CMOS settings. Its final phase is executed from the Shadow RAM area (segment E800h) and ends with the transfer of control to the operating system - code FFh.

Error code	Description of the error
82	Allocates an area in system memory for power management
83	Recovering data from a temporary storage stack in CMOS
84	Displaying the message “Initializing Plug and Play Cards...”
85	USB initialization complete
86	Reserved, Carry Flag clearing
87	Building SYSID tables in the DMI area
88	Reserved, Carry Flag clearing
89	Generating ACPI Service Tables
8A	Reserved, Carry Flag clearing
8B	Searching and initializing BIOS for additional devices
8C	Reserved, Carry Flag clearing
8D	Initializing parity bit maintenance routines
8E	Reserved, Carry Flag clearing
8F	IRQ12 resolution for mouse hot plugging 90 Reserved, clear Carry Flag
91	Initializing Legacy platform resources
92	Reserved, Carry Flag clearing
93	Presumably not used
94	Final steps to initialize the core logic before loading operating system. The power management system completes initialization. The BIOS startup screen is removed and the resource allocation table is displayed. AMD K6® family processors have specific settings. Microcode update for family processors Intel Pentium® II and higher
95	Setting the automatic transition to winter/summer time. Programming the keyboard controller for the auto-repeat frequency
96	In multiprocessor systems, final system settings are performed and service tables and fields are created. For Cyrix family processors, additional register settings are performed. Building the ESCD "Extended System Configuration Data" table. Setting the DOS Time counter in accordance with Real Time Clock. Boot device partitions are saved for further use by built-in antivirus tools: Trend AntiVirus or Paragon Anti-Virus Protection. The system speaker emits a POST completion signal. The MSIRQ table is built and saved

A number of processes occurring in the Award Medallion BIOS are designated by special groups of control points. These include:

System Event codes - control points of system events.

Power Management Debug codes are checkpoints that occur during the execution of APM or ACPI services.

System Error codes - messages about fatal errors.

Debug codes for MP system - initialization points for multiprocessor platforms.

Features of accelerated POST passage

To reduce system boot time, the user can select the "Quick Power On Self Test" option in CMOS Setup. In this case, POST will be accelerated by eliminating some procedures ( Quick Boot).

The Quick Boot operating pattern replaces the late and final POST phases and does not affect the operation of the boot block. Award Software offers a codification of the executable procedures for expedited POST that differs from the standard one. Quick Boot begins with the output of checkpoint 65h to the diagnostic port and ends with POST code 80h. Then control is transferred to the operating system with the usual Award BIOS code FFh displayed.

Error code	Description of the error
65	Early initialization of the SIO controller, software reset of the video controller. Setting up the keyboard controller, testing the keyboard and mouse. Initializing the sound controller. Checking the integrity of BIOS structures. Unpacking Flash ROM maintenance procedures. Initializing the onboard frequency synthesizer
66	Initializes the L1/L2 cache according to the results obtained from the CPUID command. Generation of a vector table consisting of pointers to interrupt handling routines. Initializing Power Management Hardware
67	Checking CMOS and battery power plausibility. Configuring chipset registers according to CMOS settings. Initializing the keyboard controller as part of the chipset. Generating BIOS Data Area Variables
68	Initializing the video system
69	Configuring i8259 interrupt controller
6A	An accelerated single-pass RAM test is performed using a special algorithm
6B	Visualization of the number of detected processors, the EPA logo and a prompt to launch the AwardFlash utility. Configuring embedded I/O controller resources in configuration mode
70	Invitations to enter Setup. Initializing PS/2 and USB Mouse
71	Initializing the cache controller
72	Setting up system logic configuration registers. Formation of the Plug and list Play devices. Initializing the FDD controller
73	Initializing the HDD controller
74	Initializing the coprocessor
75	If specified by the user in CMOS Setup, the IDE HDD is write protected.
77	Request for a password and display the message: “Press F1 to continue, DEL to enter Setup”
78	Initializing BIOS for additional devices on ISA and PCI buses
79	Initializing Legacy platform resources
7A	Generating the root table RSDT and device tables DSDT, FADT, etc.
7D	Finding information about boot device partitions
7E	Configuring BIOS services before booting the operating system
7F	Setting the NumLock flag according to CMOS SetUp
80	Transferring control to the operating system

Performing a POST in Power Saving Mode

One of the platform states, when the contents of RAM are stored on the hard disk, is called Hibernate. In the ACPI specification ("Advanced Configuration and Power Interface Specification", Revision 2.0a dated 03/31/2002) it is defined as the S4 (Non-Volatile Sleep) power saving mode. Returning to full functioning requires a special way of completing POST.

The ACPI S4 operating scheme, as with the accelerated start, replaces the late and final phases of POST. An essential point is checking the startup script in the boot block. Depending on what ACPI state the system is in after the hardware Reset signal, a decision is made to exit state S4, which begins with the output of test point 90h to the diagnostic port and ends with POST code 9Fh.

Error code	Description of the error
90	Early initialization of the SIO controller, software reset of the video controller. Setting up the keyboard controller, testing the keyboard and mouse
91	CMOS and Battery Validation Check
92	Initialization of system logic registers and on-board frequency synthesizer
93	Initializing the cache using CPUID information
94	Generation of a vector table consisting of pointers to interrupt handling routines. Initializing Power Management Hardware
95	PCI bus scanning
96	Initializing the embedded keyboard controller
97	Initializing the video system
98	VGA adapter message output
99	Checking the first channel of the DMA8237 controller by writing and test reading the base address and forwarding block length registers 9A Configuring the i8259 interrupt controller
9B	Initializing PS/2 and USB Mouse. Unpacking ACPI code. Initializing the cache controller
9C	Setting up system logic configuration registers. Generating a list of Plug and Play devices. Initialization of FDD and HDD controllers
9D	The PM region is not reserved in system memory if it is created in Shadow RAM or SMRAM. In some cases, a repeated, final initialization of the USB bus is required, performed with the L1 cache disabled
9E	Setting up Power Management, which is part of the system logic. Initialization of SMI generation circuits and installation of the SMI vector. Programming resources responsible for monitoring PM system events
9F	The disable and enable operation clears the L1/L2 cache and restores its current size. The power saving mode control settings specified in CMOS Setup are saved in PM RAM. For mobile platforms, a check is made to return to full operation after turning off all supply voltages (Zero Volt Suspend mode)

4. Phoenix BIOS 4.0 Release 6.0

Phoenix Technologies, Ltd.

One of the leaders in the development of low-level software, Phoenix Technologies, timed the release of Windows95 new version PhoenixBIOS 4.0. Family support Intel processors Pentium is reflected in the name of the intermediate revisions. One of the latest - Release 6.0 - formed the basis for all released BIOS. With the advent of Release 6.1, there were no significant changes in the execution of POST procedures, and, therefore, this did not affect the indication of checkpoints.

A distinctive feature of PhoenixBIOS is that if during the POST execution errors occur when testing 512 KB of main memory (codes 2Ch, 2Eh, 30h), additional information is output to port 80h in word format, the bits of which identify the failed address line or data cell. For example, the code "2C 0002" means that a memory fault has been detected on address line 1. The code "2E 1020" in this case will mean that a fault has been detected on data lines 12 and 5 in the low byte of the memory data bus. On 386SX systems that use a sixteen-bit data bus, it is not possible for an error to occur during code execution step 30h

The POST code output to the diagnostic port is accompanied by an audio signal output to the system speaker. The sound signal generation scheme is as follows:

• The eight-bit code is converted into four two-bit groups
• The value of each group increases by one
• Based on the received value, a short sound signal is generated (for example: code 16h = 00 01 01 10 = 1-2-2-3)

Executing startup POST procedures from ROM

Error code	Description of the error
01	Initializing the Baseboard Management Controller (BMC)
02	Checking the current processor operating mode
03	Disabling non-maskable interrupts
04	The type of installed processor is determined
06	Initial settings of the PIC and DMA registers
07	The memory area designated for the BIOS copy is reset to zero
08	Early initialization of system logic registers
09	Setting the POST software flag
0A	Initializing processor software resources
0B	Internal Cache permission
0E	Initializing Super I/O Resources
0C	Initialize L1/L2 cache according to CMOS values
0F	Initializing the IDE
10	Initializing the Power Management subsystem
11	Setting Alternate Register Values
12	The value of the MSW (Machine Status Word) register is being set.
13	Early provisioning of PCI devices
14	Initializing the Keyboard Controller
16	Checking the ROM BIOS checksum
17	Determining L1/L2 cache size
18	Initializing the 8254 system timer
1A	Initializing the DMA Controller
1C	Resetting programmable interrupt controller values
20	Checking the generation of DRAM regeneration requests
22	Checking the operation of the keyboard controller
24	Installing a selector for servicing a flat 4Gb memory model
26	A20 line resolution
28	Determining the total amount of installed memory
29	Initializing POST Memory Manager (PMM)
2A	Resetting 640Kb of main memory
2C	Testing address lines
2E	Failure on one of the data lines in the low byte of the memory data bus
2F	Selecting a cache memory protocol
30	Available system memory test
32	Determining CPU clock parameters and bus frequency

Error code	Description of the error
33	Initializing Phoenix Dispatch Manager
34	Prohibiting Power Off Using ATX Power Button
35	Settings of system logic registers that control the formation of timing characteristics of access to memory, input/output ports, system and local buses
36	A restart is performed if the transition to the next POST procedure fails. The sequence of procedures is managed by Watch Dog Service
37	The process of setting up system logic registers is completed.
38	The contents of the BIOS Runtime module are unpacked and rewritten into the area intended for Shadow RAM
39	Reinitializing the Cache Controller
3A	L2 cache resize
3B	Initializing BIOS Execution Trace
3C	Additional configuration of logic registers to configure PCI-PCI bridges and support for distributed PCI buses
3D	The system logic registers are configured in accordance with the CMOS Setup settings
3E	Read Hardware Configuration
3E	Checking the ROM Pilot system connection
40	Determining CPU clock parameters
41	Initializing ROM Pilot - remote boot control
42
44	Set BIOS Interrupt
45	Initializing devices before enabling the PnP mechanism
46	The BIOS checksum is calculated using a special algorithm
47	Initializing I2O I/O controllers
48	Search for video adapter
49	PCI Initialization
4A	Initializing system video adapters
4B	Quiet Boot is running - a shortened system startup sequence used to speed up POST.
4C	VGA BIOS contents are rewritten to the transit area
4E	Visualization of BIOS text string Copyright
4F	Reserving memory for the boot device selection menu
50	The processor type and its clock frequency are visualized
51	Initializing the EISA controller and devices
52	Keyboard Controller Programming
54	Mode activated soundtrack keys
55
58	Finding unserviced interrupt requests
59	Initializing the POST Display Service (PDS) procedure 5A Displaying the message “Press F2 to enter SETUP”
5B	Disable CPU Internal Cache
5C	Conventional Memory Check
5E	Detect Base Address
60	Extended Memory Check
62	Checking Extended Memory Address Lines
64	Transferring control to an executable block generated by the motherboard manufacturer (Patch1)
66	Configuring cache control registers
67	Minimal initialization of APIC controllers
68	L1/L2 cache resolution
69	Preparing System Management Mode RAM
6A	External Cache volume is visualized
6B	Setting CMOS Setup Defaults
6C	Visualization of Shadow RAM usage information
6E	Visualization of information about Upper Memory Blocks (UMB)
70	Displaying Error Messages
72	Checking the current system configuration and CMOS information
76	Checking Keyboard Error Information
7A	Checking the status of software (System Password) or hardware (Key Lock Switch) keyboard locking tools
7C	Setting hardware interrupt vectors
7D	Initializing the power tracking system
7E	Initializing the coprocessor
80	On-board SIO I/O controller is prohibited
81	Preparing to boot the operating system
82	Finding and identifying RS232 ports
83	Configuring external IDE controllers
84	Finding and identifying parallel ports
85	Initializing ISA PnP Devices
86	On-board resources of the SIO controller are configured in accordance with the CMOS Setup settings
87	Configuring MCD (Motherboard Configurable Devices)
88	The values ​​of the variable block in the BIOS Data Area are set
89	Allows generation of a non-maskable interrupt
8A	Setting the values ​​of variables located in the Extended BIOS Data Area
8B	Checking PS/2 Mouse connection diagrams
8C	Initializing the drive controller
8F	Determining the number of connected ATA devices
90	Initializing and configuring hard drive controllers
91	Setting temporary parameters for hard drive operation in PIO mode
92	Transferring control to an executable block generated by the motherboard manufacturer (Patch2)
93	Building a multiprocessor system configuration table
95	Selecting CD-ROM Maintenance Procedure
96	Return to Real Mode
97	Building MP Configuration Table
98	ROM Scan in progress
99	Checking the status of the SMART parameter 9A The contents of the ROM are written to RAM
9C	Setting up the Power Management subsystem
9D	Initializing resources to protect against unauthorized access
9E	Hardware interrupts are enabled
9F	The number of IDE and SCSI drives is determined
A0	Setting DOS Time based on RTC state A1 The purpose of this code is unknown A2 Checking the Key Lock state
A4	Keyboard Auto-Repeat Characteristics Settings
A8	The "Press F2 to enter Setup" message is removed from the screen
A.A.	The presence of the SCAN code of the F2 key in the input buffer AC is checked. The Setup program is launched.
A.E.	The restart flag executed by CTRL+ALT+DEL B0 is cleared. The message "Press F1 to resume, F2 to Setup" is generated.
B1	POST progress flag is cleared B2 POST completed
B4	Sound signal before booting
B5	Quiet Boot phase completed
B6	Password check if this mode is enabled in Setup B7 Initializing ACPI BIOS
B9	Search for boot devices on USB bus BA Initialize DMI parameters
BB	Repeating the ROM Scan procedure
B.C.	The RAM parity error latching trigger is reset.
BD	A menu is displayed for selecting a boot device BE Clearing the screen before loading the operating system BF Activating anti-virus support
C0	The software interrupt processing procedure INT 19h is launched - the Boot Sector loader. The interrupt service routine sequentially attempts to load the Boot Sector by polling disk devices in the order prescribed by Setup
C1	Initialization of fault maintenance routine (PEM) C2 Calling service routines for error logging
C3	Visualization of error messages in the order they were received C4 Setting initial state flags
C5	Initializing an extended block of CMOS RAM cells
C6	Initial initialization of the docking station
C7	Lazy dock initialization
C8	Execution of test procedures included in the Boot Block to determine the integrity of BIOS structures
C9	Checking the integrity of structures and/or modules external to the system BIOS
C.A.	Running Console Redirect to serve a remote CB keyboard Emulate disk devices in RAM/ROM
CC	Run Console Redirect to serve video CDs Support PCMCIA communications
C.E.	Setting up the Light Pen Controller

Fatal Error Messages

D0 Error caused by an exceptional situation (Exception error) D2 Calling an interrupt handling procedure from an unidentified source D4 Error associated with a violation of the protocol for issuing and clearing interrupt requests D6 Exiting protected mode with software reset generation D7 To save the state of the video adapter, more is required amount of memory than is available in SMRAM D8 Error during software generation of the processor reset pulse DA Loss of control when returning to Real Mode DC Exit from protected mode with software reset generation without re-initializing the interrupt controller DD Error when testing extended memory DE Keyboard controller error DF Line control error A20 19

Executing Procedures from Boot Block

Error code	Description of the error
E0	Setting up E1 chipset configuration registers Initializing the North and South Bridges
E2	Initializing the CPU
E3	Initializing the system timer
E4	Initializing Super I/O Resources
E5	Checking the status of Recovery Jumper, the installation of which forces the BIOS Recovery mode to start
E6	BIOS checksum verification
E7	Control is transferred to the BIOS if its checksum is calculated correctly E8 Initialize MPS support
E9	Transition to a flat 4Gb memory model
E.A.	Initialization of non-standard equipment
E.B.	Configuring the interrupt controller and direct memory access
E.C.	By writing and control readings using a special algorithm, the memory type is determined: FPM, EDO, SDRAM, and the Host Bridge configuration registers are configured in accordance with the result
ED	By means of records and control readings using a special algorithm, the volume of memory banks and placement in rows are determined. In accordance with the result, the Host Bridge configuration registers (DRAM Row Boundary) are configured
E.E.	The contents of the Boot Block are copied to Shadow RAM EF Preparing SMM RAM for the SMI handler
F0	Memory test
F1	Initializing interrupt vectors
F2	Initializing Real Time Clock
F3	Initializing the video subsystem
F4	Generating a beep before booting
F5	Loading the operating system stored in Flash ROM
F6	Return to Real Mode
F7	Boot to Full DOS
F8	Initializing the USB controller
FA…FF	Codes for interaction with the PhDebug procedure

5. Insyde BIOS Mobile Pro

Insyde Software Corp.

The mobile systems market insider has firmly established itself in areas where loyalty to tradition and a conservative approach to BIOS design is required. Having inherited source from SystemSoft, the company is constantly working to improve it. The latest revision of MobilePRO is actively used in Mitac and Clevo laptops, the documentation for which formed the basis of the Error Codes table - this is what Insyde Software calls POST checkpoints.

Boot block checkpoints

Despite the fact that Insyde Software created its first BIOS in 1992, the established model of the boot block - or Boot Loader, as the creators themselves called it - was finally formed only by the end of 1995. From this moment on, the starting procedure was numbered by version and creation date.

The most significant point from the point of view of a service engineer examining the loading process computer system with InsydeBIOS, the device becomes a diagnostic code display device. Although, as a rule, Boot Loader uses Manufacture's Diagnostic Port 80h, standard in such cases, in some cases, test point output is performed only on the PIO Port (Parallel Input/Output port for diagnostic purpose), which is nothing more than a parallel port 378h There are implementations in which the diagnostic codes sent to port 80h are duplicated to the parallel port.

Error code	Description of the error
00	Starting point for boot block execution 01 Inhibit line A20 (not used)
02	CPU microcode update
03	Testing RAM
04	Transferring the boot block to RAM
05	Executing a boot block from RAM
06	Forcing the Flash ROM recovery procedure
07	Transferring the system BIOS to RAM
08	System BIOS checksum verification
09	Running the POST procedure
0A	Starting the Flash ROM recovery procedure from an FDD drive
0B	Initializing the frequency synthesizer
0C	Completing the BIOS recovery procedure
0D	Alternative procedure for recovering Flash ROM from FDD
0F	Stopping if a fatal error occurs
BB	LPC SIO early initialization
CC	Starting point for starting Flash ROM recovery
88	Enabling ACPI Features
99	Error when exiting STR mode
60	Switching to Big Real Mode
61	Initialization of SM Bus. SPD data is stored in CMOS A0 Read and parse SPD fields previously stored in CMOS A1 Memory controller initialization
A2	Defining logical banks of a DIMM
A3	Programming DRB registers (DRAM Row Boundary)
A4	Programming DRA Registers (DRAM Row Attributes)
A.E.	DIMMs have been detected in the system that differ in their Error Correcting Codes (ECC) functions.
A.F.	Primary initialization of memory controller registers mapped to memory space
E1	The boot procedure fails if the DIMM is not equipped with an SPD chip
E2	DIMM type does not match system requirements
E.A.	The minimum time between activating DIMM strings and entering the regeneration state does not meet system requirements
E.C.	Register modules are not supported ED Checking CAS Latency Modes
E.E.	DIMM organization not supported by motherboard

Executing POSTs from RAM

The most modern solutions InsydeBIOS use 16-bit checkpoint mapping. This is done using ports 80h and 81h, the latter of which is intended to extend standard diagnostics.

The study of control points is made difficult by their irregular construction, when processes of different meaning are accompanied by the same codes. In dual diagnostic systems, there are differences of a different order: some POST codes are displayed only in one of the ports without the usual duplication in such cases.

Error code	Description of the error
10	Cache initialization, CMOS check
11	Line A20 prohibited. Setting registers for 8259 controllers.
12	Determining the boot method
13	Initializing the Memory Controller
14	Searching for a video adapter connected to the ISA bus
15	Setting System Timer Values
16	Setting system logic registers using CMOS
17	Calculating the total amount of RAM
18	Testing the low page of Conventional Memory
19	Verifying the checksum of the Flash ROM image
1A	Resetting the Interrupt Controller Registers
1B	Initializing the video adapter
1C	Initializing a subset of video adapter registers compatible with program model 6845
1D	Initializing the EGA adapter
1E	Initializing the CGA adapter
1F	DMA controller page register test
20	Checking the keyboard controller
21	Initializing the Keyboard Controller
22	Comparison of the resulting amount of RAM with the value in CMOS
23	Checking battery backup and Extended CMOS
24	Testing DMA Controller Registers
25	Setting DMA controller parameters
26	Formation of the interrupt vector table
27	Accelerated determination of the amount of installed memory
28	Protected Mode
29	System memory test completed
2A	Exiting Protected Mode
2B	Transferring the Setup procedure to RAM
2C	Starting the video initialization procedure
2D	Re-search for CGA adapter
2E	Re-search for EGA/VGA adapter
2F	Displaying VGA BIOS messages
30	Custom Keyboard Controller Initialization Routine
31	Checking the connected keyboard
32	Checking the passage of a request from the keyboard
33	Checking the Keyboard Status Register
34	Test and reset system memory
35	Protected Mode
36	Extended memory test completed
37	Exiting Protected Mode
38	A20 line ban
39	Initializing Cache Controller 3A Checking the System Timer
3B	Setting the DOS Time counter according to Real Time Clock
3C	Initializing the hardware interrupt table
3D	Finding and initializing manipulators and pointers
3E	Setting the status of the NumLock key
3F	Initializing serial and parallel ports
40	Configuring Serial and Parallel Ports
41	Initializing the FDD controller
42	Initializing the HDD controller
43	Initializing Power Management for the USB Bus
44	Finding and initializing additional BIOS
45	Resetting the NumLock key status
46	Checking coprocessor functionality
47	Initializing PCMCIA
48	Preparing to start the operating system
49	Transferring control to executable Bootstrap code
50	ACPI initialization
51	Initializing Power Management
52	Initializing the USB Bus Controller