Any computer repairman knows that the POST Card PCI is used to diagnose problems when repairing and upgrading computers such as IBM PC (or compatible ones).

Several companies produce such cards in Russia and the CIS: Master Kit (Moscow), e-KIT Post Cards, ACE Lab (N. Novgorod), BVG Group (Moscow), EPOS: PCI TESTCARD (Ukraine), IC Book: IC80 (Ukraine ), Jelezo: Jpost Full (Ukraine), VL Comp: PC Analyzer (Belarus). There are also foreign solutions, but we cannot find them on the open market.

POST Card PCI is a computer expansion card that can be installed in any free PCI slot (33 MHz) and is designed to display POST codes generated by the computer BIOS in a user-friendly form.

Conventionally, all POST cards can be divided into serial and non-serial (kits for self-assembly).

Review of existing POST cards

Let's look at the disadvantages of POST cards from various manufacturers.

The founder of the production of PCI POST cards in Russia is considered to be the company ACE Lab, which has a large presence in the production of software and hardware systems for diagnostics and repair of computers.

Master Keith POST Card PCI NM9221 (DIY kit)/BM9221 (finished board). One drawback is that the seven-segment indicator faces downwards.

Advantages of this POST Card: assembled on an FPGA of the EPM3XXX series, supporting Hot-socketing (more reliable, since there is less chance of burning the POST Card) and operating at 3.3V (better compatibility with modern PCI2.3 and PCI3.0 specifications), support for new and old chipsets thanks to removable firmware.

e-Kit_02 Disadvantages of this POST Card: it is assembled on an FPGA of the outdated EPM7XXX series, which does not support Hot-socketing (less reliable, since there is a greater chance of burning the POST Card) and operates at 5.0V (there may be problems with modern PCI2.3 and PCI3.0).

ACE Lab PC-POST PCI-2. It is not convenient that the indicator looks down, but it is possible to select one of 4 possible ports from which information will be read.

ACE Lab PC POWER PCI-2— a fully functional software and hardware complex that allows you to perform a number of diagnostic tests launched from the ROM installed on the board, aimed at identifying system errors and hardware conflicts.

BVG Group Dual POST. Advantages: simple and cheap POST card. Made on the basis of FPGA Altera EPM3032ALC44-10. It carries five LEDs (power supply to PCI - -12V, +12V, +3.3V, +5V, and RESET signal) and two seven-segment indicators on both sides of the board. The indicator may show one digit - this means that the PCI slot into which this POST is inserted is not receiving clocking.

A characteristic disadvantage of this card due to its stripped-down nature is the removal of clocking from the PCI slot in which this card is installed after the POST stage, at which the generator is initialized (for Award BIOS - 26h), as a result of which postcodes are no longer displayed. The methods of “fighting” this disease are as follows:

• If the BIOS Setup contains the Detect DIMM/PCI Clock item, setting it to Disable will prevent the generator from removing the frequency from unused slots, as a result of which Dual POST will work “as normal” ;), showing all the “required” postcodes.
• If the board being tested has Sharing PCI Slots (usually two connectors farthest from the processor, which have one interrupt “for two”), then you can insert any “normal” PCI device (video, audio, network, etc.) into one of them .), and in the other - a postcard. During initialization, the generator, seeing a “full-fledged” PCI device on the Sharing PCI Slots, often (depending on the specific BIOS board) does not remove the clock from both, which Dual POST will successfully “take advantage of”.

BVG Group POST Pro. Instead of seven-segment displays, an LCD display with a ticker is used, but the cost of the card is about 300 USD, which is unreasonably high.

EPOS: PCI TESTCARD. The advanced “Master” series of useful bells and whistles, by and large, only allows you to additionally select a diagnostic port in the range 0-3FFh using switches on the board, which is used to output POST codes. Disadvantages of this POST Card: it is assembled on an FPGA of the outdated EPM7XXX series, which does not support Hot-socketing (less reliable, since there is a greater chance of burning the POST Card) and operates at 5.0V (there may be problems with modern PCI2.3 and PCI3.0). There is also information about the output of incorrect POST codes on some motherboards.

IC Book: IC80. A well-known representative of “adult” postcards, the distinctive feature of which is the presence of not only “bells and whistles” in the field of monitoring, but also unique (unparalleled) capabilities for debugging the system in a step-by-step mode. The board has several distinctive features:

• Selection of addresses used for diagnostic purposes: 80h/81h and 84h/85h, 378h, 1080h
• Diagnostic codes are displayed on two indicators
• Displaying information on an external indicator
• Voltage indication Stand-By 3.3V
• PCI parity support
• Support for server PCI bus options

A small drawback: the step-by-step mode does not work quite correctly on new boards.

Jelezo: Jpost Full. On some motherboards (mainly GIGABYTE) it freezes to a black screen after the first reboot.

VL Comp: PC Analyzer. A simple and cheap post-controller, the highlight of which is the combination of two types of postcards in one design - for ISA and for PCI.

POST Card PCI BM9222 with LCD Display

Today we will look at the new generation PCI POST card POST Card PCI BM9222 produced by the Moscow company Musker Kit.

Specifications

• Supply voltage: +5 V.
• Current consumption, no more than: 100 mA.
• PCI bus frequency: 33 MHz.
• Diagnostic port address: 0080h
• Indication of POST codes: on the LCD display in two lines of 16 characters each (the first line is the POST code in hexadecimal and separated by a dash - the BIOS type, the second line is a description of the error in the form of a creeping line).
• Indication of PCI bus signals: LEDs on the front side of the board - RST (PCI reset signal) and
• CLK (PCI clock signal).
• Indicators of the presence of PCI bus supply voltages: +5V, +12V, -12V, +3.3V.
• Compatible with motherboard chipsets: Intel, VIA, SIS.
• PCB size: 95.5 x 73.6 mm.

Design

Structurally, the POST Card PCI is made on a double-sided printed circuit board made of foil fiberglass with dimensions of 95.5 x 73.6 mm. In order to improve the electrical conductivity of the device contacts, the lamellas are coated with nickel.

Operating principle of POST Card PCI

Every time you turn on the power of your IBM PC-compatible computer and before the operating system boots, the computer's processor runs a BIOS procedure called POST (Power On Self Test). The same procedure is also performed when you press the RESET button or when you soft restart the computer. To avoid misunderstandings, it should be noted here that in some special cases, in order to reduce the computer boot time, the POST procedure may be slightly shortened, for example, in Quick Boot mode or when exiting Hibernate sleep mode.

The main purpose of the POST procedure is to check the basic functions and subsystems of the computer (such as memory, processor, motherboard, video controller, keyboard, floppy and hard drives, etc.) before loading the operating system. This to some extent protects the user from trying to work on a faulty system, which could lead, for example, to the destruction of user data on the HDD. Before starting each test, the POST procedure generates a so-called POST code, which is output to a specific address in the address space of the computer's input/output devices. If a fault is detected in the device under test, the POST procedure simply freezes, and the pre-printed POST code uniquely determines which test the freeze occurred on. Thus, the depth and accuracy of diagnostics using POST codes is completely determined by the depth and accuracy of the tests of the corresponding POST BIOS procedure of the computer.

It should be noted that the POST code tables are different for different BIOS manufacturers and, due to the emergence of new tested devices and chipsets, are somewhat different even for different versions of the same BIOS manufacturer. Tables of POST codes can be found on the corresponding websites of BIOS manufacturers: for AMI this is http://www.ami.com, for AWARD - http://www.award.com, sometimes tables of POST codes are given in the manuals for motherboards.

To display POST codes in a user-friendly form, devices called POST Card are used. The proposed POST Card for the PCI bus is a computer expansion card that is inserted (with the power off!) into any free PCI slot (33 MHz) and has a text indicator for displaying POST codes and text information about the current code. Among the operating features of this POST Card, I would like to note that after turning on the computer’s power and before the first active RESET PCI signal appears, the greeting message “BM9222 MASTERKIT POSTCARD” is displayed on the POST Card indicator.

In addition, the POST Card has LEDs that reflect the status of the CLK and RST signals of the PCI bus.

Troubleshooting using POST Card PCI

The sequence of actions when repairing a computer using a POST Card is as follows:

1. Turn off the power to the faulty computer.
2. Install the POST Card into any free PCI slot on the motherboard.
3. Turn on the computer's power.
4. If necessary, adjust the contrast (when installing an LCD screen, for PLED - no adjustment required) of the image by pressing the buttons (the button farthest from the motherboard increases the contrast, the closest one decreases) or change the type of displayed BIOS - by pressing and holding one of the buttons and clicking on the second (after releasing the buttons, the BIOS type will change, displayed in the first line of the indicator after the error code). All of the above settings are saved when the power is turned off and loaded the next time power is applied to the POST Card.
5. We read the information on the POST Card indicator - this is the POST code on which the computer boots “hangs”, and its description in the second line.
6. We comprehend the probable causes.
7. With the power off, we rearrange cables, memory modules and other components in order to eliminate the malfunction.
8. Repeat steps 3-7, ensuring stable completion of the POST procedure and the start of loading the operating system.
9. Using software utilities, we carry out final testing of hardware components, and in case of floating errors, we carry out a long run of the corresponding software tests.

When repairing a computer without using a POST Card, points 3-6 of this sequence are simply omitted and from the outside, computer repair looks like just a frantic rearrangement of the memory, processor, expansion cards, power supply, and, to top it all, the motherboard.

If large companies have a large supply of serviceable components, then for small companies and individuals, computer repair by installing known-good components turns into a complex problem.

How is a computer repaired using a POST-Card carried out in practice?

First of all, when the power is turned on, before the POST procedure can begin, the system must be reset with the RST (RESET) signal, which is indicated on the POST Card by changing the greeting message to other POST Card messages. If the change does not occur within 2-4 seconds (the welcome display time is approximately 0.7 seconds) or one of the “NO CODES” or “RESET” messages appears for more than 1 second, then in this case it is recommended to immediately turn off the computer, remove all cards and cables, as well as memory modules from the motherboard. In the system unit, you must leave the motherboard with the processor installed and the POST Card connected to the power supply. If the next time you turn on the computer, the system resets normally and the first POST codes appear, then, obviously, the problem lies in the temporarily removed computer components; it is also possible in incorrectly connected loops. By sequentially inserting the memory, video adapter, and then other cards, and observing the POST codes on the indicator, a faulty module is detected.

Let us now return to the case when the initial system reset does not even go through (the POST Card indicator does not change the greeting message to other messages). In this case, either the computer's power supply is faulty, or the motherboard itself (the RESET signal generation circuits are faulty) or the processor does not start. The exact cause can be determined by connecting a known-good power supply to the motherboard.

Let us now consider the case when the reset signal passes, but no POST codes are displayed on the indicator (the “NO CODES” message is held); in this case, as described earlier, a system consisting only of a motherboard, processor, POST Card and power supply is tested. If the motherboard is completely new, then the reason may be incorrectly installed motherboard jumpers. If all jumpers and the processor are installed correctly, but the motherboard still does not start, you should replace the processor with a known good one. If this does not help, then we can conclude that the motherboard or its components are faulty (for example, the cause of the malfunction may be damaged information in the FLASH BIOS).

The main advantage of the POST Card is that it does not require a monitor to operate. At the same time, testing a computer using a POST Card is possible in the early stages of the POST procedure, when sound diagnostics are not yet available. Another important feature is the display of POST codes on all types of BIOSes that output codes at address 0x0080), but not described in the ROM.

PLED indicator

This testing device is equipped with an indicator with a PLED type display element. The advantages of this type of display are that it has high contrast and a wide viewing angle - this is very important because often a POST card has to be installed in a computer case when other cards (network, sound, etc.) are installed in adjacent slots.

Multi-language support

The POST card allows you to display codes for various types of BIOS in various languages ​​(English and Russian by default). Changing the BIOS type is carried out by simultaneously pressing both buttons. This post card decrypts 3 types of BIOSes in 2 languages ​​(6 types in total). The Russified BIOS contains the string “RU” in its name.

The lines themselves describing the codes are located on the 24C256 - 32kB SEEPROM chip. This chip is installed in the socket, and experienced users can remove it and reprogram it with another (newer or different language) version if it appears on the website www.masterkit.ru. Updates occur regularly, tracking trends in the development of computer technology.

If this code is not decrypted in your version, then you should use the Internet to quickly search for a decryption of the test type, and also write a letter to the MasterKit company indicating this case, and in the next version this code will already be included.

For reprogramming, you can use the NM9215 (programmer) kit together with an adapter for this type of chip NM9216/4.

Testing a PC system unit with a Post Card PCI tester in practice

The sequence of testing computer components is as follows:

1. CPU testing.
2. Checking the ROM BIOS checksum.
3. Check and initialize DMA, IRQ and 8254 timer controllers.
After this stage, sound diagnostics become available.
4. Checking memory regeneration operations.
5. Testing the first 64 KB of memory.
6. Loading interrupt vectors.
7. Initialization of the video controller.
After this stage, diagnostic messages are displayed on the screen.
8. Testing the full amount of RAM.
9. Keyboard testing.
10. Testing CMOS memory.
11. Initialization of COM and LPT ports.
12. Initialization and test of the FDD controller.
13. Initialization and test of the HDD controller.
14. Search for additional ROM BIOS modules and initialize them.
15. Calling the operating system loader (INT 19h, Bootstrap), if the operating system cannot be loaded, try to launch ROM BASIC (INT 18h); if unsuccessful, system shutdown (HALT).

Taking tests

When passing each of the POST tests, a POST code is generated, which is written to a special diagnostic register. The information contained in the diagnostic register becomes available for observation when the POST Card diagnostic board is installed in a free computer slot and is displayed on a seven-segment display in the form of two hexadecimal digits. The diagnostic register address depends on the type of computer, in older versions it is: ISA, EISA-80h, ISA-Compaq-84h, ISA-PS/2-90h, MCA-PS/2-680h, 80h, some EISA-300h.

First of all, you need to determine the manufacturer of the motherboard BIOS. This can be done either by a sticker on the BIOS chip, or by the inscriptions that are displayed on the screen by a similar working motherboard. In Russia and the CIS, the most common BIOS are AMI and AWARD. Once you have gained some experience, you can confidently name the BIOS manufacturer based on the first POST codes.

POST code tables are different for different BIOS manufacturers and, due to the emergence of new tested devices and chipsets, are different even for different versions of the same BIOS manufacturer.

Historically, the values ​​of POST codes in the corresponding tables of BIOS manufacturers are given as hexadecimal numbers in the range 00h-FFh (0-255 in the decimal system), therefore, for the convenience of using such tables, it is necessary to ensure that POST codes are displayed in hexadecimal form.

Fault codes

Award Software International, Inc.

AwardBIOS V4.51PG Elite

The dynamically developing company Award Software in 1995 proposed a new solution at that time 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.

Executing startup POST procedures from ROM

C0 External Cache prohibition. Internal Cache prohibition. Ban Shadow RAM. Programming DMA controller, interrupt controller, timer, RTC block

C1 Determining the type of memory, total volume and placement by lines

C3 Checking the first 256K DRAM for the Temporary Area organization. Unpacking BIOS in Temporary Area

C5 Running POST code is moved to Shadow

C6 Determining the presence, size and type of External Cache

C8 Checking the integrity of BIOS programs and tables

CF Determining the processor type

Performing a POST in Shadow RAM

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 Checking and initializing the keyboard controller

06 Test the memory area starting at address F000h, where the BIOS is located

07 Checking CMOS and battery operation

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 Generation of interrupt vector table. 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 Testing 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 System Timer Channel 2 Test

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 an NMI Interrupt Request

30 Determining the volume of Base Memory and Extended Memory. APIC setup. Software control of Write Allocation mode

Preparing tables, arrays and structures for starting the operating system

31 The main on-screen RAM test. 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 External Cache Controller Initialization and Cache Permissions

B.F. Setting up 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 Initializing serial and parallel ports

45 Initializing the FPU coprocessor

4E Error message display

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 Setting the DOS Time counter according to Real Time Clock

60 Installing BOOT Sector antivirus protection

61 Final steps to initialize the chipset

62 Reading keyboard ID. Setting its parameters

63 Correction of ESCD, DMI blocks. Clearing RAM

FF Transferring control to the bootloader. BIOS executes INT 19h command

Let's consider the procedure for testing the system unit of a personal computer. Let's install the BM9222 tester into a free PCI slot on the motherboard. Let's turn on the power. BIOS is a computer boot program stored in the motherboard ROM that sequentially polls all devices included in the system unit (processor, memory modules, hard drive, video card, controllers, optical drive, external peripherals: keyboard, mouse, etc.).

If all peripheral devices of the system unit are working properly, then after loading is complete, the following inscription FFh will light up on the tester screen.

“Let’s introduce a fault” into the system unit. Turn off the power and remove the memory module from the system unit.

After power is applied and the computer boots, the RAM error code 4Eh appears on the tester screen.

The tester accurately determined that the memory in the system unit is “faulty.” After turning off the power and returning the memory module to its place, the tester showed the health of the personal computer.

Similarly, you can determine the error codes of other peripheral devices and quickly resolve the problem by replacing the faulty unit with a working one.

conclusions

Description:

I bring to your attention the main POST codes forBIOSmanufacturerAMI. A short introduction. Immediately after pressing the POWER button on the system unit of the personal computer, control of the PC goes directly to the BIOS. At this time (at the beginning of the PC startup), the processor sends a signal to the BIOS chip, which initializes the loading of the BOOT-ROUTINE firmware of the Basic I/O System.
The BOOT-ROUTINE firmware calls the POST self-test routine.

Subroutine POST (Power-On Self Test) tests the equipment installed on the computer, configures it and prepares it for work.

A separate test is performed for each individual piece of equipment (processor, memory, video card, keyboard, input/output ports, etc.). Each test has its own unique number, which is called a POST code. POST code written to the Manufacturing Test Port (with address 0080H) before running each individual POST test.

After the POST test code is written to the Manufacturing Test Port, the testing procedure for the corresponding equipment begins. If the testing procedure fails, the POST code of the last procedure (which caused the error) remains in the Manufacturing Test Port. If you know the POST code of the last procedure, you can determine the device that caused the error.

Reading POST codes can be done in several ways.

• If your motherboard has a built-in POST code indicator, information about the POST code of the last procedure can be found from it.
• On some systems, the POST code of the last procedure performed may be displayed on the monitor screen during the POST procedure.
• A special expansion card can be used to read POST codes.

Since BIOS is produced by several manufacturers, each BIOS from an individual manufacturer has its own table of POST codes.

This table contains POST codes that are displayed during the full POST procedure.

• CF Detects processor type and tests CMOS read/write
• C0 The chipset and L1-, L2-cache are pre-initialized, the interrupt controller, DMA, timer are programmed
• C1 The type and amount of RAM is detected
• C3 BIOS code is unpacked into a temporary area of ​​RAM
• 0C BIOS checksums are checked
• C5 BIOS code is copied to shadow memory and control is transferred to the Boot Block module
• 01 XGROUP module is unpacked at physical address 1000:0000h
• 02 Processor initialization. The CR and MSR registers are set
• 03 I/O resources are determined (Super I/O)
• 05 Clears screen and CMOS status flag
• 06 Coprocessor is being checked
• 07 Keyboard controller is identified and tested
• 08 Keyboard interface is detected
• 09 Initializing the Serial ATA controller
• OA Detects the keyboard and mouse that are connected to the PS/2 ports
• 0B AC97 audio controller resources are being installed
• OE Testing memory segment F000h
• 10 The type of flash memory is determined
• 12 CMOS tested
• 14 Sets values ​​for chipset registers
• 16 The clock generator is initially initialized
• 18 The processor type, its parameters and L1 and L2 cache sizes are determined
• 1B The interrupt vector table is initialized
• 1C Checks CMOS checksums and battery voltage
• 1D Power management system is defined
• 1F Loads the keyboard matrix (for laptops)
• 21 The Hardware Power Management system is initializing (for laptops)
• 23 Math coprocessor, disk drive, chipset initialization are tested
• 24 The processor microcode is being updated. Creates a resource distribution map for Plug and Play devices
• 25 Initial PCI initialization: lists devices, searches for VGA adapter, writes VGA BIOS to C000:0
• 26 The clock frequency is set according to CMOS Setup. Synchronization of unused DIMM and PCI slots is disabled. The monitoring system (H/W Monitor) is initialized
• 27 Interrupt INT 09h enabled. The keyboard controller is initialized again
• 29 MTRR registers are programmed, APIC is initialized. The IDE controller is being programmed. The processor frequency is measured. The video system BIOS extension is called
• 2B Search for video adapter BIOS
• 2D The Award splash screen is displayed, information about the processor type and its speed
• 33 Keyboard reset
• 35 First DMA channel being tested
• 37 Second DMA channel being tested
• 39 DMA page registers are tested
• 3C Configuring 8254 controller (timer)
• 3E Checking the 8259 interrupt controller
• 43 Interrupt controller is checked
• 47 ISA/EISA buses are tested
• 49 The amount of RAM is calculated. Registers are being configured for the AMD K5 processor
• 4E MTRR registers are programmed for Syrix processors. L2 cache and APIC are initialized
• 50 USB bus detected
• 52 The RAM is tested and the results are displayed. Clearing extended memory
• 53 If the CMOS is cleared, the login password is reset
• 55 Displays the number of processors (for multiprocessor platforms)
• 57 The EPA logo is displayed. Initial Initialization of ISA PnP Devices
• 59 Virus protection system is determined
• 5B Prompt for running BIOS update from floppy disk
• 5D Launches Super I/O controller and integrated audio controller
• 60 Entering CMOS Setup if the Delete key was pressed
• 65 PS/2 mouse is initializing
• 69 L2 cache enabled
• 6B Chipset registers are configured according to BIOS Setup
• 6D Assigns resources for ISA PnP devices and COM ports for integrated devices
• 6F Initializes and configures the floppy disk controller
• 75 IDE devices are detected and installed: hard drives, CD/DVD, LS-120, ZIP, etc.
• 76 Information about detected IDE devices is displayed
• 77 Serial and parallel ports are initialized
• 7A The math coprocessor is reset and ready for operation.
• 7C Defines protection against unauthorized writing to hard drives
• 7F If there are errors, a message is displayed and the Delete and F1 keys are pressed
• 82 Memory is allocated for power management and changes are written to the ESCD table.
• The splash screen with the EPA logo is removed. Requests a password if needed
• 83 All data is saved from the temporary stack to CMOS
• 84 Displaying Initializing Plug and Play Cards message
• 85 USB initialization complete
• 87 SYSID tables are created in the DMI area
• 89 ACPI tables are being installed. Interrupts are assigned to PCI devices
• 8B Called by the BIOS of additional ISA or PCI controllers, with the exception of the video adapter
• 8D Sets RAM parity parameters using CMOS Setup. APM is initialized
• 8F IRQ 12 is allowed for hot plugging of a PS/2 mouse
• 94 Completion of chipset initialization. Displays the resource allocation table. Enable L2 cache. Setting the summer/winter time transition mode
• 95 Sets the keyboard auto-repeat frequency and Num Lock state
• 96 For multiprocessor systems, registers are configured (for Cyrix processors). The ESCD table is created. The DOS Time timer is set according to the RTC CMOS clock. Boot device partitions are saved for use by the built-in antivirus. The speaker announces the end of POST. The MSIRQ FF table is created. The BIOS INT 19h interrupt is executed. Search for the bootloader in the first sector of the boot device

A shortened procedure is performed by setting the Quick Power On Self Test option in the BIOS.

• 65 The video adapter is being reset. The sound controller and input/output devices are initialized, the keyboard and mouse are tested. BIOS integrity is checked
• 66 Cache is initializing. An interrupt vector table is created. The power management system is initializing
• 67 The CMOS checksum is checked and the battery is tested. The chipset is configured based on CMOS parameters
• 68 Video adapter is initializing
• 69 Configuring the interrupt controller
• 6A Testing RAM (accelerated)
• 6B Displays EPA logo, CPU and memory test results
• 70 A prompt to enter BIOS Setup is displayed. A mouse connected to PS/2 or USB is initialized
• 71 Cache controller is initializing
• 72 Chipset registers are being configured. A list of Plug and Play devices is created.& The drive controller is initialized
• 73 Hard disk controller is initializing
• 74 Coprocessor is initializing
• 75 If necessary, the hard drive is write-protected
• 77 If necessary, a password is requested and messages Press F1 to continue, DEL to enter Setup are displayed
• 78 Expansion cards with their own BIOS are initialized
• 79 Platform resources are initializing
• 7A The root table RSDT, device tables DSDT, FADT, etc. are generated.
• 7D Collects information about boot device partitions
• 7E BIOS is preparing to boot the operating system
• 7F The NumLock indicator status is set according to the settings
• BIOS Setup
• 80 INT 19 is called and the operating system starts

AMIBIOS8.0

• D0 Initialization of the processor and chipset. Verifying BIOS boot block checksums
• D1 Initialization of I/O ports. The command for the BAT self-test is sent to the keyboard controller
• D2 Disable L1/L2 cache. The amount of installed RAM is determined
• D3 Memory regeneration schemes are configured. Allowed to use cache memory
• D4 Test 512 KB memory. The stack is installed and the communication protocol with the cache memory is assigned
• D5 BIOS code is unpacked and copied to shadow memory
• D6 Checks BIOS checksums and pressing Ctrl+Home keys (BIOS recovery)
• D7 Control is transferred to the interface module, which unpacks the code into the Run-Time area
• D8 The executable code is unpacked from flash memory into operational memory. CPUID information is saved
• D9 The unpacked code is transferred from the temporary storage area to segments 0E000h and 0F000h of RAM
• DA CPUID registers are restored. POST execution is moved to RAM
• E1–E8, EC–EE Errors related to the system memory configuration
• 03 Processing of NMI, parity errors, and output of signals to the monitor is prohibited. An area is reserved for the GPNV event log, the initial values ​​of variables from the BIOS are set
• 04 Checks battery health and calculates CMOS checksum
• 05 The interrupt controller is initialized and the vector table is built
• 06 The timer is being tested and prepared for operation
• 08 Keyboard testing (keyboard lights flashing)
• C0 Initial processor initialization. Do not use cache memory. Defined by APIC
• C1 For multiprocessor systems, the processor responsible for starting the system is determined
• C2 Completes the assignment of the processor to start the system. Identification using CPUID
• C5 The number of processors is determined and their parameters are configured
• C6 Initializes cache memory for faster POST.
• C7 Processor initialization completes
• 0A Keyboard controller detected
• 0B Search for a mouse connected to the PS/2 port
• 0C Checking for keyboard presence
• 0E Various input devices are detected and initialized
• 13 Initial initialization of chipset registers
• 24 Platform-specific BIOS modules are unpacked and initialized.
• An interrupt vector table is created and interrupt processing is initialized.
• 2A The DIM mechanism identifies devices on local buses. The video adapter is being prepared for initialization, a resource distribution table is being built
• 2C Detection and initialization of the video adapter, the video adapter is called by the BIOS
• 2E Finding and initializing additional I/O devices
• 30 Prepares for SMI processing
• 31 ADM module is initialized and activated
• 33 The simplified loading module is initializing
• 37 Displays AMI logo, BIOS version, processor version, key prompt to enter BIOS
• 38 Using DIM, various devices on local buses are initialized
• 39 DMA controller is initializing
• 3A Sets the system time according to the RTC clock
• 3B RAM is tested and results are displayed
• 3C Chipset registers are configured
• 40 Serial and parallel ports, mathematical coprocessor, etc. are initialized.
• 52 Based on the results of the memory test, the RAM data in CMOS is updated
• 60 In BIOS Setup, the NumLock state is set and auto-repeat parameters are configured
• 75 The procedure for working with disk devices is started (interrupt INT 13h)
• 78 A list of IPL devices is created (from which the operating system can be loaded)
• 7C ESCD extended system configuration tables are created and written to NVRAM
• 84 Log errors encountered during POST
• 85 Messages are displayed about detected non-critical errors.
• 87 If necessary, BIOS Setup is launched, which is first unpacked into RAM
• 8C Chipset registers are configured in accordance with BIOS Setup
• 8D ACPI tables are built
• 8E Configures non-maskable interrupt (NMI) service
• 90 SMI is finally initialized
• A1 Clearing data that is not needed when loading the operating system
• A2 EFI modules are prepared to interact with the operating system
• A4 In accordance with the BIOS Setup language module is initialized
• A7 The POST procedure summary table is displayed
• A8 Sets the state of the MTRR registers
• A9 If necessary, waits for keyboard commands to be entered
• AA Removes POST interrupt vectors (INT 1Ch and INT 09h)
• AB Devices for loading the operating system are detected
• AC The final stages of setting up the chipset in accordance with BIOS Setup
• B1 ACPI interface is configured
• 00 Interrupt processing INT 19h is called (boot sector search, OS loading)

Phoenix Bios 4.0

• 02 Verify Real Mode
• 03 Disable Non-Maskable Interrupt (NMI)
• 04 Get CPU type
• 06 Initialize system hardware
• 08 Initialize chipset with initial POST values
• 09 Set IN POST flag
• 0A Initialize CPU registers
• 0B Enable CPU cache
• 0C Initialize caches to initial POST values
• 0E Initialize I/O component
• 0F Initialize the local bus IDE
• 10 Initialize Power Management
• 11 Load alternate registers with initial POST values
• 12 Restore CPU control word during warm boot
• 13 Initialize PCI Bus Mastering devices
• 14 Initialize keyboard controller
• 16 (1-2-2-3) BIOS ROM checksum
• 17 Initialize cache before memory autosize
• 18 8254 timer initialization
• 1A 8237 DMA controller initialization
• 1C Reset Programmable Interrupt Controller
• 20 (1-3-1-1) Test DRAM refresh
• 22 (1-3-1-3) Test 8742 Keyboard Controller
• 24 Set ES segment register to 4 GB
• 26 Enable A20 line
• 28 Autosize DRAM
• 29 Initialize POST Memory Manager
• 2A Clear 512 KB base RAM
• 2C (1-3-4-1) RAM failure on address line xxxx
• 2E (1-3-4-3) RAM failure on data bits xxxx of low byte of memory bus
• 2F Enable cache before system BIOS shadow
• 30 (1-4-1-1) RAM failure on data bits xxxx of high byte of memory bus
• 32 Test CPU bus-clock frequency
• 33 Initialize Phoenix Dispatch Manager
• 34 Disable Power Button during POST
• 35 Re-initialize registers
• 36 Warm start shut down
• 37 Re-initialize chipset
• 38 Shadow system BIOS ROM
• 39 Re-initialize cache
• 3A Autosize cache
• 3C Advanced configuration of chipset registers
• 3D Load alternate registers with CMOS values
• 40 CPU speed detection
• 42 Initialize interrupt vectors
• 45 POST device initialization
• 46 (2-1-2-3) Check ROM copyright notice
• 48 Check video configuration against CMOS
• 49 Initialize PCI bus and devices
• 4A Initialize all video adapters in system
• 4B QuietBoot start (optional)
• 4C Shadow video BIOS ROM
• 4E Display BIOS copyright notice
• 50 Display CPU type and speed
• 51 Initialize EISA board
• 52 Test keyboard The keyboard is being tested
• 54 Set key click if enabled
• 55 Initialize USB bus
• 58 (2-2-3-1) Test for unexpected interrupts
• 59 Initialize POST display service
• 5A Display prompt “Press F2 to enter SETUP”
• 5B Disable CPU cache
• 5C Test RAM between 512 and 640 KB
• 60 Test extended memory
• 62 Test extended memory address lines
• 64 Jump to UserPatch1
• 66 Configure advanced cache registers
• 67 Initialize Multi Processor APIC
• 68 Enable external and CPU caches
• 69 Setup System Management Mode (SMM) area
• 6A Display external L2 cache size
• 6B Load custom defaults (optional)
• 6C Display shadow-area message
• 6E Display possible high address for UMB recovery
• 70 Display error messages Error messages are displayed
• 72 Check for configuration errors
• 76 Check for keyboard errors
• 7C Set up hardware interrupt vectors
• 7D Initialize hardware monitoring
• 7E Initialize coprocessor if present
• 80 Disable onboard Super I/O ports and IRQs
• 81 Late POST device initialization
• 82 Detect and install external RS232 ports
• 83 Configure non-MCD IDE controllers
• 84 Detect and install external parallel ports
• 85 Initialize PC-compatible PnP ISA devices
• 86 Re-initialize onboard I/O ports
• 87 Configure Motheboard Configurable Devices (optional)
• 88 Initialize BIOS Data Area
• 89 Enable Non-Maskable Interrupts (NMIs)
• 8A Initialize Extended BIOS Data Area
• 8B Test and initialize PS/2 mouse
• 8C Initialize floppy controller
• 8F Determine number of ATA drives (optional)
• 90 Initialize hard-disk controllers
• 91 Initialize local-bus harddisk controllers
• 92 Jump to UserPatch2
• 93 Build MPTABLE for multi-processor boards
• 95 Install CD ROM for boot
• 96 Clear huge ES segment register
• 97 Fixup Multi Processor table
• 98 (1-2) Search for option ROMs. One long, two short beeps on checksum failure
• 99 Check for SMART Drive (optional)
• 9A Shadow option ROMs
• 9C Set up Power Management
• 9D Initialize security engine (optional)
• 9E Enable hardware interrupts
• 9F Determine number of ATA and SCSI drives
• A0 Set time of day
• A2 Check key lock
• A4 Initialize Typematic rate
• A8 Erase F2 prompt
• AA Scan for F2 key stroke
• AC Enter SETUP
• AE Clear Boot flag
• B0 Check for errors
• B2 POST done – prepare to boot operating system
• B4 (1) One short beep before boot
• B5 Terminate QuietBoot (optional)
• B6 Check password (optional)
• B9 Prepare Boot
• BA Initialize DMI parameters
• BB Initialize PnP Option ROMs
• BC Clear parity checkers
• BD Display MultiBoot menu
• BE Clear screen (optional)
• BF Check virus and backup reminders
• C0 Try to boot with INT 19
• C1 Initialize POST Error Manager (PEM)
• C2 Initialize error logging
• C3 Initialize error display function
• C4 Initialize system error handler
• C5 PnPnd dual CMOS (optional)
• C6 Initialize notebook docking (optional)
• C7 Initialize notebook docking late
• D2 Unknown interrupt
• E0 Initialize the chipset
• E1 Initialize the bridge
• E2 Initialize the CPU
• E3 Initialize system timer
• E4 Initialize system I/O
• E5 Check force recovery boot
• E6 Checksum BIOS ROM
• E7 Go to BIOS
• E8 Set Huge Segment
• E9 Initialize Multi Processor
• EA Initialize OEM special code
• EB Initialize PIC and DMA
• EC Initialize Memory type
• ED Initialize Memory size
• EE Shadow Boot Block
• EF System memory test
• F0 Initialize interrupt vectors
• F1 Initialize Real Time Clock
• F2 Initialize video
• F3 Initialize System Management Mode
• F4 (1) Output one beep before boot
• F5 Boot to Mini DOS
• F6 Clear Huge Segment
• F7 Boot to Full DOS

Original and reliable tables of POST codes can be found on the corresponding websites of BIOS manufacturers: “AMI” and “Award”. Sometimes POST code tables are provided in motherboard manuals.
1. Test of software-accessible processor registers (POST codes: 01, 02).
2. Checking the RAM regeneration period (POST code: 04).
3. Initialize the keyboard controller (POST code: 05).
4. Preliminary check of the performance of non-volatile memory (CMOS) and the condition of the CMOS battery (POST code: 07).
5. Initialization of chipset registers with default values ​​(POST code: BE, hex).
6. Checking the presence and determining the size of RAM (POST code: C1, hex).
7. Determining the presence and size of external cache memory (POST code: C6, hex).
8. Checking the first 64 KB of RAM (POST code: 08).
9. Initialization of interrupt vectors (POST code: 0A, hex).
10. Checking the CMOS checksum (POST code: 0V, hex).
11. Detection and initialization of the video controller (POST code: 0D, hex).
12. Video memory check (POST code: 0E, hex).
13. Checking the BIOS checksum (POST code: 0F, hex).
14. Checking controllers and DMA page registers (POST codes: 10,
11, hex).
15. Checking the system timer (POST code: 14, hex).
16. Checking and initializing interrupt controllers (POST codes: 15...18, hex).
17. Initialization of expansion bus slots (POST codes: 20...2F, hex).
18. Determining the size and checking the main and extended memory (POST codes: 30, 31, hex).
19. Re-initialize the chipset registers in accordance with the values ​​​​set in CMOS Setup (POST code: BF, hex).
20. Initialization of the FDD controller (POST code: 41, hex).
21. Initialization of the HDD controller (POST code: 42, hex).
22. Initialization of COM and LPT ports (POST code: 43, hex).
23. Detection and initialization of the math coprocessor (POST code: 45, hex).
24. Checking whether a password is required (POST code: 4F, ​​hex).
25. Initializing BIOS extensions (POST code: 52, hex).
26. Setting the Virus Protect, Boot Speed, NumLock, Boot Attempt parameters in accordance with the values ​​​​set in CMOS Setup (POST codes: 60...63, hex).
27. Calling the operating system boot procedure (POST code: FF, hex).
As can be seen from the above sequence, the ability to display diagnostic messages on the monitor screen appears only after the video controller is initialized, and if the POST procedure stopped at one of the previous stages, then it is not possible to see at which one.

Compaq BIOS:

	Error Message	Description
		System is booting properly
	BIOS ROM checksum error	The contents of the BIOS ROM to not match the expected contents. If possible, reload the BIOS from the PAQ
		Check the video adapter and ensure it"s seated properly. If possible, replace the video adapter
7 beeps (1 long, 1s, 1l, 1 short, pause, 1 long, 1 short, 1 short)		The AGP video card is faulty. Reseat the card or replace it outright. This beep pertains to Compaq Deskpro systems
1 long never ending beep		Memory error. Bad RAM. Replace and test
		Reseat RAM then retest; replace RAM if failure continues

IBM Desktop BIOS:

	Error Message	Description
		System is booting properly
	Initialization error	Error code is displayed
	System board error
	Video adapter error
	EGA/VGA adapter error
	3270 keyboard adapter error
	Power supply error	Replace the power supply
	Power supply error	Replace the power supply
		Replace the power supply

IBM Thinkpad BIOS:

Beeps/Error	Description
Continuous beeping	System board failure
One beep; Unreadable, blank or flashing LCD	LCD connector problem; LCD backlight inverter failure; video adapter faulty; LCD assembly faulty; System board failure; power supply failure
One beep; Message "Unable to access boot source"	Boot device failure; system board failure
One long, two short beeps	System board failure; Video adapter problem; LCD assembly failure
One long, four short beeps	Low battery voltage
One beep every second	Low battery voltage
Two short beeps with error codes	POST error message
	System board failure

IBM Intellistation BIOS:

Beep error code:	Action / Run diagnostics on the following components:
1-1-3 CMOS read/write error	1.Run Setup 2.System Board
1-1-4 ROM BIOS check error	1.System Board
1-2-X DMA error	1.System Board
1-3-X	1.Memory Module 2.System Board
1-4-4	1. Keyboard 2.System Board
1-4-X Error detected in first 64 KB of RAM.	1.Memory Module 2.System Board
2-1-1, 2-1-2	1.Run Setup 2.System Board
2-1-X First 64 KB of RAM failed.	1.Memory Module 2.System Board
2-2-2	2.System Board
2-2-X First 64 KB of RAM failed.	1.Memory Module 2.System Board
2-3-X	1.Memory Module 2.System Board
2-4-X	1.Run Setup 2. Memory Module 3.System Board
3-1-X DMA register failed.	1.System Board
3-2-4 Keyboard controller failed.	1.System Board 2. Keyboard
3-3-4 Screen initialization failed.	1. Video Adapter (if installed) 2.System Board 3.Display
3-4-1 Screen retrace detected an error.	1. Video Adapter (if installed) 2.System Board 3.Display
3-4-2 POST is searching for video ROM.	1. Video Adapter (if installed) 2.System Board
4	1. Video Adapter (if installed) 2.System Board
All other beep code sequences.	1.System Board
One long and one short beep during POST. Base 640 KB memory error or shadow RAM error.	1.Memory Module 2.System Board
One long beep and two or three short beeps during POST.(Video error)	1. Video Adapter (if installed) 2.System Board
Three short beeps during POST.	1. See "System board memory" on page 62. 2.System Board
Continuous beep.	1.System Board
Repeating short beeps.	1. Keyboard stuck key? 2.Keyboard Cable 3.System Board

Mylex BIOS:

	Error Message	Description
		System is booting normally
	Video adapter error	The video adapter is either faulty or not seated properly. Check the adapter
	Keyboard controller error	The keyboard controller IC is faulty. Replace the IC if possible
		The keyboard controller IC is faulty or the keyboard is faulty. Replace the keyboard, if problem still persists, replace the keyboard controller IC
		The programmable interrupt controller is faulty. Replace the IC if possible
		The programmable interrupt controller is faulty. replace the IC if possible
	DMA page register error	The DMA controller IC is faulty. Replace the IC if possible
	RAM refresh error
	RAM parity error
	DMA controller 0 error	The DMA controller IC for channel 0 has failed
		The CMOS RAM has failed
	DMA controller 1 error	The DMA controller IC for channel 1 has failed
	CMOS RAM battery error	The CMOS RAM battery has failed. If possible, replace the CMOS or battery
	CMOS RAM checksum error	The CMOS RAM has failed. If possible, replace the CMOS
	BIOS ROM checksum error	The BIOS ROM has failed. If possible replace the BIOS or upgrade it

Mylex 386 BIOS:

	Error Message	Description
		System is booting normally
	Video adapter failure	Either the video adapter is faulty, not seated properly or is missing
1 long, 1 short, 1 long	Keyboard controller error	Either the keyboard controller IC is faulty or the system board circuitry is faulty
1 long, 2 short, 1 long		Either the keyboard controller is faulty or the system board circuitry is faulty
1 long, 3 short, 1 long
1 long 4 short, 1 long		The programmable interrupt controller IC is faulty
1 long, 5 short, 1 long	DMA page register error	The DMA controller IC 1 or 2 is faulty or the system board circuitry is faulty
1 long, 6 short, 1 long	RAM refresh error
1 long, 7 short, 1 long
1 long, 8 short, 1 long	RAM parity error
1 long, 9 short, 1 long	DMA controller 1 error	The DMA controller for channel 0 is faulty or the system board circuitry is faulty
1 long, 10 short, 1 long		Either the CMOS RAM is faulty. Replace the CMOS
1 long, 11 short, 1 long	DMA controller 2 error	The DMA controller for channel 1 is faulty or the system board circuitry is faulty
1 long, 12 short, 1 long	CMOS RAM battery error	The CMOS RAM battery is faulty or the CMOS RAM is bad. Replace the battery if possible
1 long, 13 short, 1 long	CMOS checksum error	The CMOS RAM is faulty
1 long 14 short, 1 long	BIOS ROM checksum failure	The BIOS ROM checksum is faulty. Replace the BIOS or upgrade

Phoenix ISA/MCA/EISA BIOS:

The beep codes are represented in the number of beeps. E.g. 1-1-2 would mean 1 beep, a pause, 1 beep, a pause, and 2 beeps.

• With a Dell computer, a 1-2 beep code can also indicate that a bootable add-in card is installed but no boot device is attached. For example, in you insert a Promise Ultra-66 card but do not connect a hard drive to it, you will get the beep code. I verified this with a SIIG (crap -- avoid like the plague) Ultra-66 card, and then confirmed the results with Dell.

	Error Message	Description
	CPU test failure	The CPU is faulty. Replace the CPU
	System board select failure	The motherboard is having an undetermined fault. Replace the motherboard
	CMOS read/write error	The real time clock/CMOS is faulty. Replace the CMOS if possible
	Extended CMOS RAM failure	The extended portion of the CMOS RAM has failed. Replace the CMOS if possible
	BIOS ROM checksum error	The BIOS ROM has failed. Replace the BIOS or upgrade if possible
		The programmable interrupt timer has failed. Replace if possible
	DMA read/write failure	The DMA controller has failed. Replace the IC if possible
	RAM refresh failure	The RAM refresh controller has failed
	64KB RAM failure	The test of the first 64KB RAM has failed to start
	First 64KB RAM failure	The first RAM IC has failed. Replace the IC if possible
	First 64KB logic failure	The first RAM control logic has failed
	Address line failure	The address line to the first 64KB RAM has failed
	Parity RAM failure	The first RAM IC has failed. Replace if possible
	EISA fail-safe timer test	Replace the motherboard
	EISA NMI port 462 test	Replace the motherboard
	64KB RAM failure	Bit 0; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 1; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 2; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 3; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 4; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 5; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 6; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 7; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 8; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 9; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 10; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 11; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 12; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 13; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 14; This data bit on the first RAM IC has failed. Replace the IC if possible
	64KB RAM failure	Bit 15; This data bit on the first RAM IC has failed. Replace the IC if possible
	Slave DMA register failure	The DMA controller has failed. Replace the controller if possible
	Master DMA register failure	The DMA controller had failed. Replace the controller if possible
	Master interrupt mask register failure
	Slave interrupt mask register failure	The interrupt controller IC has failed
	Interrupt vector error	The BIOS was unable to load the interrupt vectors into memory. Replace the motherboard
	Keyboard controller failure
	CMOS RAM power bad	Replace the CMOS battery or CMOS RAM if possible
	CMOS configuration error	The CMOS configuration has failed. Restore the configuration or replace the battery if possible
	Video memory failure	There is a problem with the video memory. Replace the video adapter if possible
	Video initialization failure	There is a problem with the video adapter. Reseat the adapter or replace the adapter if possible
		The system's timer IC has failed. Replace the IC if possible
	Shutdown failure	The CMOS has failed. Replace the CMOS IC if possible
	Gate A20 failure	The keyboard controller has failed. Replace the IC if possible
	Unexpected interrupt in protected mode	This is a CPU problem. Replace the CPU and retest
	RAM test failure	System RAM addressing circuitry is faulty. Replace the motherboard
	Interval timer channel 2 failure	The system timer IC has failed. Replace the IC if possible
	Time of day clock failure	The real time clock/CMOS has failed. Replace the CMOS if possible
	Serial port failure	A error has occurred in the serial port circuitry
	Parallel port failure	A error has occurred in the parallel port circuitry
	Math coprocessor failure	The math coprocessor has failed. If possible, replace the MPU

	Description
	Verify real mode
	Initialize system hardware
	Initialize chipset registers with initial values
	Set in POST flag
	Initialize CPU registers
	Initialize cache to initial values
	Initialize power management
	Load alternative registers with initial POST values
	Jump to UserPatch0
	Initialize timer initialization
	8254 timer initialization
	8237 DMA controller initialization
	Reset Programmable Interrupt Controller
	Test DRAM refresh
	Test 8742 Keyboard Controller
	Set ES segment register to 4GB
	Clear 512K base memory
	Test 512K base address lines
	Test 51K base memory
	Test CPU bus-clock frequency
	CMOS RAM read/write failure (this commonly indicates a problem on the ISA bus such as a card not seated)
	Reinitialize the chipset
	Shadow system BIOS ROM
	Reinitialize the cache
	Autosize the cache
	Configure advanced chipset registers
	Load alternate registers with CMOS values
	Set initial CPU speed
	Initialize interrupt vectors
	Initialize BIOS interrupts
	Check ROM copyright notice
	Initialize manager for PCI Options ROMs
	Check video configuration against CMOS
	Initialize PCI bus and devices
	initialize all video adapters in system
	Shadow video BIOS ROM
	Display copyright notice
	Display CPU type and speed
	Set key click if enabled
	Test for unexpected interrupts
	Display prompt "Press F2 to enter setup"
	Test RAM between 512K and 640K
	Test expanded memory
	Test extended memory address lines
	Jump to UserPatch1
	Configure advanced cache registers
	Enable external and CPU caches
	Initialize SMI handler
	Display external cache size
	Display shadow message
	Display non-disposable segments
	Display error messages
	Check for configuration errors
	Test real-time clock
	Check for keyboard errors
	Setup hardware interrupt vectors
	Test coprocessor if present
	Disable onboard I/O ports
	Detect and install external RS232 ports
	Detect and install external parallel ports
	Reinitialize onboard I/O ports
	Initialize BIOS Data Area
	Initialize Extended BIOS Data Area
	Initialize floppy controller
	Initialize hard disk controller
	Initialize local bus hard disk controller
	Jump to UserPatch2
	Disable A20 address line
	Clear huge ES segment register
	Search for option ROMs
	Shadow option ROMs
	Setup power management
	Enable hardware interrupts
	Scan for F2 keystroke
	Clear in-POST flag
	Check for errors
	POST done - prepare to boot operating system
	Check password (optional)
	Clear global descriptor table
	Clear parity checkers
	Check virus and backup reminders
	Try to boot with INT 19
	Interrupt handler error
	Unknown interrupt error
	Pending interrupt error
	Initialize option ROM error
	Extended Block Move
	Shutdown 10 error
	Keyboard Controller failure (most likely problem is with RAM or cache unless no video is present)
	Initialize the chipset
	Initialize refresh counter
	Check for Forced Flash
	Do a complete RAM test
	Do OEM initialization
	Initialize interrupt controller
	Read in bootstrap code
	Initialize all vectors
	Initialize the boot device
	Boot code was read OK

Quadtel BIOS:

	Error Messages	Description
		System is booting normally
		The CMOS RAM is faulty. Replace the IC if possible
		The video adapter is faulty. Reseat the video adapter or replace the adapter if possible
	Peripheral controller error	One or more of the system peripheral controllers is bad. Replace the controllers and retest

A POST card or POST tester is a PCI expansion card that has a digital indicator that displays motherboard initialization codes. Using this code, you can find which of the board components has a malfunction. The codes often depend on the BIOS manufacturer. If there are no errors and the test is successful, then POST produces a code that does not change the value, for example, on most motherboards
When initialization is completed, the code “FF” is displayed. Testers are also often equipped with LEDs that display voltages +5 +3.3 +12, −12.

Here are the error codes suitable for most BIOS versions:

POST code	Description
D0	Pre-initialization of the motherboard and processor chipset. Checking the BIOS checksum. Disable non-maskable NMI interrupt. The Super I/O controller is being checked and the CMOS is being checked.
D1	The keyboard controller performs a self-test (BAT test). Initial initialization of the I/O ports is performed. Initializing the DMA controller.
D2	Disable the use of cache memory. The procedure for determining the amount of installed RAM is performed.
D3	The generation of requests for dynamic RAM regeneration is checked. Enable the use of cache memory.
D4	Testing 512 KB of memory. The stack address is set and the cache memory is configured.
D5	The system BIOS code is unpacked and rewritten into Shadow RAM.
D6	The BIOS checksum is calculated and the Ctrl+Home key combination is checked. If at least one of these conditions is met, the BIOS recovery procedure starts.
D7	If the BIOS checksums are successfully verified, control is transferred to the InterfaceModule, which unpacks the executable code into the Run-Time area.
D8	The Run-Time code is unpacked from flash memory into RAM. The CPUID information is stored in RAM.
D9	The unpacked Run-Time code is transferred from the temporary storage area to RAM. Control is transferred to the unpacked module.
D.A.	The CPUID registers are being restored. The POST procedure is in progress.
E0	Initializing floppy drive controller registers. The interrupt controller is initialized and interrupt vectors are set. Enable L1 cache.
E9	Setting up floppy drive registers.
E.A.	The read operation from ATAPI CD-ROM and disk memory is checked.
E.B.	Return to checkpoint E9 in case of errors during operations with ATAPI CD-ROM.
E.F.	Return to EB checkpoint if errors occur during disk operations.
F0	It looks for a recovery file named AMIBOOT.ROM.
F1	A transition is made to point F1 if the recovery file is not found.
F5	Disable L1 cache.
FB	FlashROM type definition. Search the FlashROM for a section for storing chipset settings.
F4	A transition is made to point F4 if the recovery file named AMIBOOT.ROM has an incorrect size.
F.C.	Resetting the main Flash BIOS block.
FD	The main Flash BIOS block is being programmed.
FF	The FF point is moved to if Flash BIOS programming has been successfully completed. Writing to FlashROM is prohibited. ATAPI hardware is being disabled. The CPUID value is restored.
03	Processing of non-maskable interrupts (NMI) and checking of RAM parity errors are prohibited. The data area of ​​the current BIOS execution and POST is initialized.
04	Checking the CMOS checksum and battery voltage.
05	The interrupt controller is initialized and the interrupt vector table is generated.
06	Preparing for the interval timer to work.
08	The keyboard controller performs a self-test (BAT test). Initializing the CPU.
C0	Disable the use of cache memory. APIC controller initialization. Preparing the processor for operation.
C1	Configuring processor operation parameters.
C2	Identifying the processor using the CPUID command.
C5	Determining the number of processors and setting their parameters.
C6	Initializing the processor cache.
C7	Completing the initialization process of the central processor.
0A	Initializing the keyboard controller.
0B	Searches for a mouse connected via the PS/2 interface.
0C	Searching for a keyboard.
0E	Finding and initializing I/O devices. Interrupt capture INT 09h. Displays the BIOS logo on the screen.
13	The initial initialization of the chipset registers is performed.
24	The BIOS modules are unpacked and initialized. Preparing to initialize the interrupt vector table.
25	Completed initialization of the interrupt vector table.
2A	Devices are initialized on local buses (using the DIM-Device Initialization Manager mechanism). Preparing to initialize the video adapter.
2C	Finding and initializing the video card.
2E	Additional I/O devices are searched for and initialized.
30	The SMI (System Management Interrupt) component is initializing.
31	Unpacking the ADM module. Initialization and activation of ADM.
33	Initializing the bootloader module.
37	Displays the AMI logo, information about the BIOS version, information about the type of processor and its speed on the monitor screen. Displays on the monitor the name of the key that can be used to enter Bios Setup.
38	Devices are initialized on local buses (using the DIM-Device Initialization Manager mechanism).
39	The DMA controller is initializing.
3A	Set the system time according to the Real Time Clock (RTC).
3B	The RAM is tested and the test results are then displayed on the monitor.
3C	Setting up chipset registers.
40	The math coprocessor, parallel and serial ports are initialized.
50	The memory control modules are being adjusted.
52	The information in CMOS about the amount of RAM is adjusted (according to the results of the RAM test).
60	Programming the keyboard controller for the auto-repeat frequency and the waiting time before entering auto-repeat mode according to the BIOS Setup settings. Setting the state of the Numlock indicator according to the BIOS Setup settings.
75	The INT 13h interrupt is being initialized, which is used to work with disk devices.
78	A list of devices from which you can boot the OS is created.
7A	The remaining BIOS extensions are being initialized.
7C	Creating and saving the ESCD table.
84	A report is being compiled on errors that were detected during the POST procedure.
85	Displays information on the monitor about errors detected during the POST procedure.
87	At this stage, it is possible to enter the BIOS Setup program.
8C	Setting up chipset registers.
8D	The ACPI table is being built.
8E	Maintenance of NMI interrupts. Configuring peripheral device parameters.
90	Final SMI initialization in progress
A0	Request for a boot password (if this is provided in the BIOS Setup settings).
A1	This clears data that is not required to boot the OS.
A2	Preparing EFI modules.
A4	The language module is initializing.
A7	Displaying a table of the final results of completing the POST procedure.
A8	Programming MTRR (Memory Type Range Register) registers.
A9	Waiting for keyboard commands to be entered.
A.A.	Resetting interrupts INT 1C, INT 09. Disabling the procedure maintenance module (ADM).
AB	Determining devices from which you can boot the OS.
A.C.	The final stage of initializing the chipset registers in accordance with the BIOS Setup parameters
B1	The ACPI interface is being configured.
00	Performing BIOS INT 19h interrupt. Control of the boot process is transferred to the operating system loader. The OS starts loading.

POST (Power-On Self-Test) - self-testing of the main components of the computer after switching on, performed by special program code in the BIOS. As you know, the POST procedure is an important part of initializing computer hardware. It precedes the launch of vital computer components, its start. However, as a result of a breakdown or incorrect BIOS settings, the computer may refuse to start. What to do then? After all, in this case, no diagnostic messages are displayed on the screen. Diagnostics will come to the rescue and decoding of audio postcodes. If you are repairing a computer with your own hands for the first time, a brief table of decoding postcodes and associated faults will be a good help.

Decoding audio post-signals, POST BIOS signals

Below is post signal decoding list quite common Avard BIOS In working condition, the speaker located on the motherboard emits only a short beep. In the event of a malfunction of one or another component (but not the motherboard itself), the speaker produces a series of sound signals, the postcodes of which we will now decipher.

POST beep sequence	Description of the error
1 short	Successful POST
2 short	Minor errors have been detected. A prompt appears on the monitor screen to enter the CMOS Setup Utility program and correct the situation. The keyboard may not be connected or is faulty
3 long.	Keyboard controller error
1 short, 1 long.	RAM memory error
1 long, 2 short	Video card error
1 long, 3 short.	No video card or video memory error (video card is faulty)
1 long, 9 short.	Error when reading from ROM (the chip in which the BIOS program is written)
Repeating short	Problems with RAM memory
Repeating long.	RAM problems
Repeated high-low frequency.	CPU problems
Continuous.	Problems with the power supply

PCI Postcard. Decoding postcard codes

Decoding the beeper (speaker) codes makes sense if the motherboard is working. If it fails, we will get complete silence. In this case, a postmap will come to the rescue.

Decoding postcard codes in PDF format available at .

Video of a Chinese pci postcard working on an Altera FPGA