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Thread: BIOS Power-On Self Test (POST)

  1. #1
    HeadShot Master N1nja Cybr1d's Avatar
    Join Date
    Jul 2003
    Boston, MA

    BIOS Power-On Self Test (POST)

    This information is taken from various valid sources and its not all in my own words. I'm posting it to hopefully help some1 who has any problems with their comps.

    BIOS stands for Basic Input/Output System, although the full term is used very infrequently. The system BIOS is the lowest-level software in the computer; it acts as an interface between the hardware (especially the chipset and processor) and the operating system. The BIOS provides access to the system hardware and enables the creation of the higher-level operating systems (DOS, Windows 95, etc.) that you use to run your applications. The BIOS is also responsible for allowing you to control your computer's hardware settings, for booting up the machine when you turn on the power or hit the reset button, and various other system functions.

    No beep Power supply, system board
    1 short beep System OK
    2 short beeps POST Error displayed on monitor
    Repeating short beeps Power supply, system board
    3 long beeps 3270 keyboard card
    1 long, 1 short beeps System board
    1 long, 2 short beeps Display adapter (MDA, CGA)
    1 long, 3 short beeps EGA
    Continuous beep Power supply, system board

    Note: Some POST errors are considered "fatal" while others are not. A fatal error means that it will halt the boot process immediately (an example would be if no system memory at all is found). In fact, most POST boot errors are fatal, since the POST is testing vital system components

    Beep(s) Failure
    1 short DRAM refresh
    2 short Parity circuit
    3 short Base 64K RAM
    4 short System timer
    5 short Processor
    6 short Keyboard controller Gate A20 error
    7 short Virtual mode exception error
    8 short Display memory R/W test
    9 short ROM BIOS checksum
    1 long, 3 short Non-fatal--Conventional/extended memory
    1 long, 8 short Non-fatal--Display/retrace test

    Beep Non-Fatal Failures* code
    4-2-1 Timer tick interrupt test (or in progress)
    4-2-2 Shutdown test (or in progress)
    4-2-3 Gate A20 failure
    4-2-4 Unexpected interrupt in protected mode
    4-3-1 RAM test in progress or address failure > FFFFh
    4-3-3 Interval timer Channel 2
    4-3-4 Time-of-day clock (or test)
    4-4-1 Serial port (or test)
    4-4-2 Parallel port (or test)
    4-4-3 Math coprocessor (or test)
    low 1-1-2 System-board select
    low 1-1-3 Extended CMOS RAM

    Beep Fatal Failures* Beep code
    1-1-3 CMOS write/read (or real-time clock read/write)
    1-1-4 ROM BIOS checksum
    1-2-1 Programmable interval timer
    1-2-2 DMA initialization
    1-2-3 DMA page register write/read
    1-2-4 SRAM test and configuration (or test)
    1-3-1 RAM refresh verification
    1-3-3 1st 64kb RAM chip or data line failure, multibit
    1-3-4 First 64K RAM odd/even logic
    1-4-1 Address line failure first 64K RAM
    1-4-2 Parity failure first 64K RAM
    2-1-1 Bit 0 first 64K RAM
    2-1-2 Bit 1 first 64K RAM
    2-1-3 Bit 2 first 64K RAM
    2-1-4 Bit 3 first 64K RAM
    2-2-1 Bit 4 first 64K RAM
    2-2-2 Bit 5 first 64K RAM
    2-2-3 Bit 6 first 64K RAM
    2-2-4 Bit 7 first 64K RAM
    2-3-1 Bit 8 first 64K RAM
    2-3-2 Bit 9 first 64K RAM
    2-3-3 Bit 10 first 64K RAM
    2-3-4 Bit 11 first 64K RAM
    2-4-1 Bit 12 first 64K RAM
    2-4-2 Bit 13 first 64K RAM
    2-4-3 Bit 14 first 64K RAM
    2-4-4 Bit 15 first 64K RAM
    3-1-1 Slave DMA register
    3-1-2 Master DMA register
    3-1-3 Master interrupt mask register failure
    3-1-4 Slave interrupt mask register failure
    3-2-4 Keyboard controller test failure
    3-3-4 Screen initialization
    3-4-1 Screen retrace
    3-4-2 Search for video ROM in progress (not failure)


    1 short Begin POST and End POST
    1 long, 1 short Floppy Disk Drive or Controller Failure
    Continuous short Parity Error in First 64K RAM
    Continuous tone First 64K RAM failure
    1 long Keyboard Failed or Locked, Interrupt or other system board error
    long short, long short, long short Video Initialization Failure, or Invalid Video Switch Setting

    Post Codes for EuroBIOS v4.71
    03 DMA Page registers OK
    04 DMA Page registers failed
    05 Keyboard did reply
    06 Keyboard did not reply
    07 Keyboard self-test passed
    08 Keyboard self-test failed
    09 8042 was able to read links
    0A 8042 was unable to read links
    0B RATMON/DIAG link OK
    0C Keyboard accepted 60h command
    0D Keyboard did not accept 60h
    0E Keyboard parameter accepted
    0F Keyboard parameter not accepted
    10 Able to read keyboard command byte
    11 Unable to read keyboard command byte
    12 Keyboard command byte came back OK
    13 Keyboard command byte came back corrupt
    14 RAM refresh clock ticking correctly
    15 RAM refresh clock not ticking correctly
    16 RAM bit test passed
    17 RAM bit test failed
    18 RAM parity OK
    19 RAM parity error
    1A CMOS RAM passed
    1B CMOS RAM failed
    1C CMOS RAM battery OK
    1D CMOS RAM battery faulty
    1E CMOS RAM checksum passed
    1F CMOS RAM checksum failed
    20 CMOS RAM battery fault bit set
    21 DMA controllers passed
    22 DMA controller 1 failed
    23 DMA controller 2 failed
    24 Protected mode entered safely
    25 RAM test completed
    26 ROM checksum correct
    27 ROM checksum incorrect
    28 Protected mode exit successful
    29 Keyboard power-up reply received
    2A Keyboard power-up reply not received
    2B Keyboard disable command accepted
    2C Keyboard disable command not accepted
    2D No video display
    2E Reported errors
    2F About to halt
    30 Protected mode entered safely
    31 RAM test complete
    32 PIC 1 (master) passed
    33 PIC 1 (master) failed
    34 PIC 2 (slave) passed
    35 PIC 2 (slave) failed
    36 Chipset initialised OK
    37 Chipset initilize failed
    38 Shadowed BIOS OK
    39 Shadowed BIOS failed
    3A Shadowed video BIOS OK
    3B Shadowed video BIOS failed

    I hope this helps.

  2. #2
    AO übergeek phishphreek's Avatar
    Join Date
    Jan 2002
    It was nice of you to compile all this info for us.
    I know that you stated that you took this from various sources and it is not all in your own words... so you really should put links to where you found this data.

    Plus it would be good for people having problems because they would have more info from the links that you did not include with your tutorial.
    Quitmzilla is a firefox extension that gives you stats on how long you have quit smoking, how much money you\'ve saved, how much you haven\'t smoked and recent milestones. Very helpful for people who quit smoking and used to smoke at their computers... Helps out with the urges.

  3. #3
    Senior Member
    Join Date
    Nov 2001

    other than your disclaimer and farewell, exactly what words ARE yours?

    plagiarism is not condoned here. at least re-write the paragraphs in your oun words and like phish says list your sources | or die
    Bukhari:V3B48N826 “The Prophet said, ‘Isn’t the witness of a woman equal to half of that of a man?’ The women said, ‘Yes.’ He said, ‘This is because of the deficiency of a woman’s mind.’”

  4. #4
    HeadShot Master N1nja Cybr1d's Avatar
    Join Date
    Jul 2003
    Boston, MA
    lol tedob....sorry for not putting the links....i was just surfing around and visited a site with this info...also...just the IBM information was from me which I got from a computer repair class i took in high school (worksheet). I'll be much more careful next time.

  5. #5
    Senior Member
    Join Date
    Nov 2001
    thanks! we all put allot of time in effort into writing tutorials. So when someone comes along and just copies and pastes something, speaking for myself, it really pisses me off. Its not really necessary to put "much" work into one just as long as its your own.
    Bukhari:V3B48N826 “The Prophet said, ‘Isn’t the witness of a woman equal to half of that of a man?’ The women said, ‘Yes.’ He said, ‘This is because of the deficiency of a woman’s mind.’”

  6. #6
    Join Date
    Aug 2001
    *Moved from Tutorials*

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