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:

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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