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POST Error Beep Codes

Every time a computer is switched on it performs a short diagnostic routine known as the POST, or Power On Self Test. The POST is a small program contained in the BIOS. It checks that basic hardware is present and performs a rudimentary memory test. The POST announces the results of its routine both audibly (a series of beeps on the PC speaker) and visually (displaying a brief summary or codes on the screen).

The audible method is essential since a fault may exist with the graphics card or monitor. If all is well, the computer typically emits a single beep and carries on booting. The number and duration of the beeps is intended as a coded message and understanding them will allow you to diagnose any problems the computer may have.

The codes vary according to the manufacturer of the BIOS. Here are some of the more common codes:


AMI I Award I IBM I Phoenix

AMI BIOS

Number and Duration of Beeps

Message

one short DRAM refresh failure (Problem with memory)
two short Parity circuit failure
three short Base 64K RAM failure
four short System Timer failure
five short Processor failure
six short Keyboard Controller / Gate A20 failure
seven short Virtual Mode Exception error
eight short Display Memory Read/Write failure (fault with video card)
nine short ROM BIOS Checksum error (fault with BIOS chip)
ten short CMOS Shutdown Read/Write error
eleven short Cache memory
one long Passed (no errors)
one long, two short Video failure
one long, three short Base / Extended Memory failure
one long, eight short Display / Retrace Test failure

Award BIOS

Number and Duration of Beeps

Message

one short Passed (no errors)
two short Any non-fatal error
one long, two short Video failure
one long, three short Keyboard Controller failure (applies to 286, 386 and 486)

IBM BIOS

Number and Duration of Beeps

Message

none Power Supply or System Board failure (possible short)
one short Passed (no errors)
one short (blank screen) Video error (check cable)
one short (no boot) Floppy Drive error
two short Configuration Error (displayed on screen)
repeating short Power Supply or System Board failure
continuous Power Supply or System Board / Keyboard stuck
one long, one short System Board failure
one long, two short Video (Mono/CGA) failure (check cable)
one long, three short Video (EGA) failure (check cable)
three long Keyboard Card error

Phoenix BIOS

Number of Beeps

Message

one, one, three CMOS Read/Write
one, one, four ROM BIOS Checksum failure
one, two, one Programmable Interval Timer failure
one, two, two DMA Initialisation failure
one, two, three DMA Page Register Read/Write failure
one, three, one RAM Refresh Verification error
one, three, three First 64K RAM Chip/Data Line failure
one, three, four First 64K RAM Odd/Even Logic
one, four, one First 64K RAM: Address Line
one, four, two First 64K RAM: Parity failure
one, four, three Fail-Safe Timer Feature (EISA only)
one, four, four Software NMI Port failure (EISA only)
two (followed by various combinations) First 64K RAM Chip/Data Line failure (combinations indicate which bit)
three, one, one Slave DMA Register failure
three, one, two Master DMA Register failure
three, one, three Master Interrupt Mask Register failure
three, one, four Slave Interrupt Mask Register failure
three, two, four Keyboard Controller failure
three, three, four Display Memory failure
three, four, one Display Retrace failure
three, four, two Video ROM search proceeding
four, two, one Timer Tick failure
four, two, two Shutdown failure
four, two, three Gate A20 failure
four, two, four Unexpected Interrupt in Protected Mode
four, three, one RAM test above 64K failure
four, three, two/three Programmable Interval Timer, Channel 2 failure
four, three, four Realtime Clock failure
four, four, one Serial Port error
four, four, two Parallel Port error
four, four, three Math Co-processor failure
(tone) one, one, two System Board Select
(tone) one, one, three Extender CMOS RAM

 

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